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  • 101
    Electronic Resource
    Electronic Resource
    Theory of free-electron maser with two-dimensional distributed feedback driven by an annular electron beam (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1619-1629 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The use of two-dimensional (2D) distributed feedback is considered as a method of providing spatially coherent radiation from an oversized annular electron beam. To realize the feedback mechanism, 2D Bragg structures formed from doubly-corrugated waveguide sections of coaxial geometry are suggested. The properties of two types of coaxial cavities formed using such structures are compared: a single-section 2D Bragg cavity and a two-mirror cavity. The eigenmodes of both cavities are found and their high selectivity over both azimuthal and longitudinal indices was demonstrated. Time-domain analyses of the excitation of the cavities by an annular electron beam were carried out. The influence of the cavity parameters on the oscillation regime is analyzed and discussed. It was shown that for a specific set of 2D Bragg cavity parameters it is possible to obtain a regime of steady-state oscillations when the transverse size of the beam exceeds the wavelength by a few orders of magnitude, while outside this parameter space multimode oscillation takes place. The design of a 2D Bragg free-electron maser oscillator based on a high-current accelerator at the University of Strathclyde is discussed. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1481193
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  • 102
    Electronic Resource
    Electronic Resource
    Sensitivity of reflection transducers (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1630-1642 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This article discusses the sensitivity of new high-speed optical transducers for measuring acoustic transients propagating in water. These devices are based upon the measurement of reflectance at a solid–water interface using a probe beam, perturbations in reflected intensity being brought about by the changes in pressure from an acoustic transient traversing the boundary. It is found that the sensitivity of such transducers is highly dependent not only upon the angle of incidence of the probe beam used to measure reflectance, but also the divergence of the probe beam and the acoustic properties of the transducer material. This results in a trade off between obtaining high spatial resolution and high sensitivity with such a transducer, and higher sensitivities give rise to a more nonlinear response. The fabrication and calibration of a robust prototype transducer made out of perspex is discussed and initial experimental results measuring acoustic transients associated with laser cavitation are shown. High spatial resolution and sensitivity were achieved by focusing the probe beam onto the interface at an angle which was slightly smaller than the critical angle. Finally, a transducer with yet higher sensitivity fabricated out of glass is demonstrated, allowing the study of smaller amplitude rarefaction waves. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1489497
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  • 103
    Electronic Resource
    Electronic Resource
    Ultrafast electron optics: Propagation dynamics of femtosecond electron packets (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1643-1648 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Time-resolved electron diffraction harbors great promise for resolving the fastest chemical processes with atomic level detail. The main obstacles to achieving this real-time view of a chemical reaction are associated with delivering short electron pulses with sufficient electron density to the sample. In this article, the propagation dynamics of femtosecond electron packets in the drift region of a photoelectron gun are investigated with an N-body numerical simulation and mean-field model. It is found that space-charge effects can broaden the electron pulse to many times its original length and generate many eV of kinetic energy bandwidth in only a few nanoseconds. There is excellent agreement between the N-body simulation and the mean-field model for both space-charge induced temporal and kinetic energy distribution broadening. The numerical simulation also shows that the redistribution of electrons inside the packet results in changes to the pulse envelope and the development of a spatially linear axial velocity distribution. These results are important for (or have the potential to impact on) the interpretation of time-resolved electron diffraction experiments and can be used in the design of photoelectron guns and streak tubes with temporal resolution of several hundred femtoseconds. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1487437
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  • 104
    Electronic Resource
    Electronic Resource
    Growth kinetics and mechanisms of aluminum-oxide films formed by thermal oxidation of aluminum (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1649-1656 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The growth kinetics and mechanisms of thin aluminum-oxide films formed by the dry, thermal oxidation of a bare Al(431) substrate at a partial oxygen pressure of 1.33×10−4 Pa in the temperature range of 373–773 K were studied using x-ray photoelectron spectroscopy. The initial oxidation of the bare Al substrate proceeds by an island-by-layer growth mechanism, involving the lateral diffusion over the bare Al substrate surface of mobile oxygen species. At low temperatures (T≤573 K), an amorphous oxide film develops that attains a limiting (uniform) thickness. At high temperatures (T〉573 K), growth is not impeded at a limiting thickness. Kinetic analysis established the occurrences of two different oxide-film growth regimes: an initial regime of very fast oxide-film growth and a second, much slower oxidation stage that is observed only at T〉573 K. These results could be discussed in terms of electric-field controlled, interstitial, outward transport of Al cations through a close packing of O anions in the amorphous films, and inward diffusion of O along grain boundaries in the crystalline films, respectively. For the electric-field controlled Al cation motion, a value of 2.6 eV was determined for the rate-limiting energy barrier, which is located at the metal/oxide interface. This corresponds with a Mott potential of −1.6 V. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1491591
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  • 105
    Electronic Resource
    Electronic Resource
    Electron collision cross sections for tetraethoxysilane (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1663-1667 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We describe the development of a consistent set of low-energy electron-collision cross sections for tetraethoxysilane, also known as tetraethylorthosilicate. Ab initio calculations are used to obtain the elastic and momentum-transfer cross sections. These are combined with measured values of the ionization cross section and with model vibrational and electronic excitation cross sections to form a preliminary cross section set, which is then adjusted to achieve consistency with measured swarm parameters. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1491024
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  • 106
    Electronic Resource
    Electronic Resource
    Measured cross sections and ion energies for a CHF3 discharge (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1657-1662 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Trifluoromethane (CHF3) is used in semiconductor plasma processing chambers to achieve high-etch selectivity of an oxide layer over a silicon substrate. Such surface etching is governed by the ion and molecule fluxes near the surface, the concentrations of which are dependent upon species interactions in and their transport through the plasma. In order to assist in the interpretation of ion flux measurements and to provide fundamental data required for plasma modeling, we report the first total cross sections for significant ion-molecule reactions occurring in CHF3 discharges. The reactions studied include collision-induced dissociation for CF3+ on CHF3, dissociative charge transfer for CF3+ and F+ on CHF3, and electron detachment from F− on CHF3. Collision energies range from a few to a few hundred electron volts. In addition, ion-flux energy distributions and relative ion intensities have been measured and are presented for dc townsend discharges with E/N values ranging from 5×10−18 to 25×10−18 V m2 [5 to 25 kTd]. The townsend discharge results are qualitatively interpreted using the cross-section measurements. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1491276
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  • 107
    Electronic Resource
    Electronic Resource
    Improving solar cell efficiencies by down-conversion of high-energy photons (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1668-1674 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: One of the major loss mechanisms leading to low energy conversion efficiencies of solar cells is the thermalization of charge carriers generated by the absorption of high-energy photons. These losses can largely be reduced in a solar cell if more than one electron–hole pair can be generated per incident photon. A method to realize multiple electron–hole pair generation per incident photon is proposed in this article. Incident photons with energies larger than twice the band gap of the solar cell are absorbed by a luminescence converter, which transforms them into two or more lower energy photons. The theoretical efficiency limit of this system for nonconcentrated sunlight is determined as a function of the solar cell's band gap using detailed balance calculations. It is shown that a maximum conversion efficiency of 39.63% can be achieved for a 6000 K blackbody spectrum and for a luminescence converter with one intermediate level. This is a substantial improvement over the limiting efficiency of 30.9%, which a solar cell exposed directly to nonconcentrated radiation may have under the same assumption of radiative recombination only. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1492021
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  • 108
    Electronic Resource
    Electronic Resource
    Space-charge-limited current in electron diodes under the influence of collisions (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1690-1698 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An analytical theory is given for the space-charge-limited (SCL) current of an electron diode in the presence of collisions. It extends the improved SCL current formula, which already takes into account the effect of nonzero electron injection velocities v0, by treating collisions within a simple model, with a friction parameter ν. The general current–voltage characteristic is obtained numerically. Within the Child–Langmuir limit v0→0, however, our model not only recovers analytically both the ballistic Child–Langmuir law (as ν(very-much-less-than)1) and the nonballistic drift Mott–Gurney law (as ν(very-much-greater-than)1), but also provides SCL for any ν. Based on the present analysis, the nonreflective nature of SCL is emphasized. Extensive use is made of the Lagrangian description of the cold-fluid equations and from proper knowledge about the correct definition of the SCL. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1490616
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  • 109
    Electronic Resource
    Electronic Resource
    Nondegenerate monopole mode of single defect two-dimensional triangular photonic band-gap cavity (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 654-659 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The two-dimensional monopole mode is investigated as a candidate for a nondegenerate photonic band-gap (PBG) cavity mode. This monopole mode formed in a single defect triangular PBG cavity is truly nondegenerate and remains nondegenerate in the sense that the introduction of asymmetry does not result in splitting of the mode. Several methods to tune the resonant frequency of the mode are studied. The radii, positions, and shapes of the nearest-neighbor air holes are varied in this analysis using the three-dimensional finite-difference time-domain calculation. The quality factor of the monopole mode formed in a slab waveguide structure is found to be larger than that of the dipole mode when the shape of the nearest-neighbor holes is elliptical. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1481965
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  • 110
    Electronic Resource
    Electronic Resource
    Amorphous silicon waveguides for microphotonics (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 649-653 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Amorphous silicon a-Si was made by ion irradiation of crystalline silicon with 1×1015 Xe ions cm−2 at 77 K in the 1–4 MeV energy range. Thermal relaxation of the amorphous network at 500 °C for 1 h leads to an amorphous layer with a refractive index of n=3.73, significantly higher than that of crystalline silicon (n=3.45 at λ=1.55 μm). a-Si can thus serve as a waveguide core in Si based optical waveguides. Channel waveguides were made by anisotropic etching of a 1.5 μm silicon-on-insulator structure that was partly amorphized. Transmission measurements of these waveguides as function of the amorphous silicon length show that the a-Si part of the waveguides exhibit a modal propagation loss of 70 cm−1 (0.03 dB μm−1) and a bulk propagation loss of 115 cm−1 (0.05 dB μm−1). Losses due to sidewall roughness are estimated, and are negligible compared to the modal loss. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1486055
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  • 111
    Electronic Resource
    Electronic Resource
    Strain-electric field hysteresis measurement in a Pb0.65Ba0.35Nb2O6 thin film using optical reflection (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1168-1170 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a simple method using direct laser beam reflection from the MgO substrate of a PBN:65 thin film to measure strain–electric field hysteresis produced by electric field-induced bending. We obtained both the strain–electric field and time–electric field relationships from these hysteresis curves. In addition, we determined time constants for strain saturation, obtained a quadratic relationship between strain and electric field, and calculated a value of 0.000 875 μm2/V2 for the electrostrictive constant. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1489709
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  • 112
    Electronic Resource
    Electronic Resource
    Improved light extraction from emitters in high refractive index materials using solid immersion lenses (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 660-665 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Solid immersion lenses (SILs) are optically transparent, truncated spheres, brought in contact with a sample to be imaged. The combination of a conventional optical microscope and a SIL results in a highly effective numerical aperture of the imaging system that can improve the resolution. In addition, when imaging high refractive index samples, such as semiconductors, the light collection efficiency can be increased drastically. We investigate the collection efficiency as a function of the SILs geometry and refractive index, using an analytical expression for the light dispersion through an arbitrarily truncated sphere. The theoretical results are compared to experimental measurements obtained on single quantum dots and are found to be in good agreement. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1487913
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  • 113
    Electronic Resource
    Electronic Resource
    Dissociative recombination coefficient for low temperature equilibrium cesium plasma (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 690-697 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The dissociative recombination (DR) coefficient in decaying low temperature Cs plasma is calculated based on the experimentally measured relaxation time of decaying Cs plasma by L. P. Harris [J. Appl. Phys. 36, 1543 (1965)]. Results showed that DR is the dominant recombination process over three-body recombination at T〈1650 K and PCs of 0.5–20 Torr (67–2666 Pa). The estimated DR coefficient for Cs is between 10−12 and 10−13 m3/s at T〈1750 K and PCs of 0.5–20 Torr. Although theory predicts that DR coefficient solely depends on temperature, the present results show pressure dependency. For typical operating conditions in thermionic converters (T〈1650 K and PCs≤400 Pa), DR is constant and ∼5.26×10−13 m3/s. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1486250
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  • 114
    Electronic Resource
    Electronic Resource
    Effects of NH3 and N2 additions to hot filament activated CH4/H2 gas mixtures (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 672-681 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Resonance enhanced multiphoton ionization and cavity ring down spectroscopies have been used to provide spatially resolved measurements of relative H atom and CH3 radical number densities, and NH column densities, in a hot filament (HF) reactor designed for diamond chemical vapor deposition and here operating with a 1% CH4/n/H2 gas mixture—where n represents defined additions of N2 or NH3. Three-dimensional modeling of the H/C/N chemistry prevailing in such HF activated gas mixtures allows the relative number density measurements to be placed on an absolute scale. Experiment and theory both indicate that N2 is largely unreactive under the prevailing experimental conditions, but NH3 additions are shown to have a major effect on the gas phase chemistry and composition. Specifically, NH3 additions introduce an additional series of "H-shift" reactions of the form NHx+H(r harp over l)NHx−1+H2 which result in the formation of N atoms with calculated steady state number densities 〉1013 cm−3 in the case of 1% NH3 additions in the hotter regions of the reactor. These react, irreversibly, with C1 hydrocarbon species forming HCN products, thereby reducing the concentration of free hydrocarbon species (notably CH3) available to participate in diamond growth. The deduced reduction in CH3 number density due to competing gas phase chemistry is shown to be compounded by NH3 induced modifications to the hot filament surface, which reduce its efficiency as a catalyst for H2 dissociation, thus lowering the steady state gas phase H atom concentrations and the extent and efficiency of all subsequent gas phase transformations. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1481961
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  • 115
    Electronic Resource
    Electronic Resource
    Diagnostics of nanosecond dynamics of the plasma produced during KrF excimer laser ablation of zirconia in vacuum (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 666-671 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A 248 nm KrF excimer laser was used to ablate the yttria stabilized ZrO2 target in vacuum while an intensified charge coupled device camera was used to get the time-resolved side view images of the induced plume/plasma. Two components, plume and plasma, can be clearly distinguished from the images with delay time less than 300 ns. The center of the plasma is found moving along the direction tilted ∼55°, instead of 90°, from the surface of the target while the processing laser came along ∼40°. The movement velocities and the explosion rates of the plasma during the first 2 μs after the laser strike were calculated. Time- and spatial-resolved emission spectra from excited Zr atoms in the plasma have been measured to determine the corresponding excitation temperature. The dynamic evolution of the plasma is outlined based on the experimental results. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1483394
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  • 116
    Electronic Resource
    Electronic Resource
    Vacuum ultraviolet emission dynamics of a coplanar electrode microdischarge: dependence on voltage and Xe concentration (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 682-689 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report nanosecond time-resolved measurements of the vacuum ultraviolet (VUV) emission and current waveforms for a planar, surface-discharge plasma display electrode in Xe/Ne mixtures. The 173 nm excimer emission is separately resolved from the overall VUV emission by a removable fused silica filter. The time difference between the maximum of excimer emission and that of resonant atomic emission is measured at high Xe concentration. The decay time of the overall VUV emission decreases strongly as the Xe concentration increases due to three-body collisions leading to Xe2 formation. The decay time constants versus Xe concentration and pressure are measured and compared with published rate constants. The efficiency of VUV emission increases rapidly from 4% to 10% Xe, but only marginally with further increase to 30% Xe. For fixed Xe ratio, the VUV emission efficiency drops with increasing driving voltage. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1486041
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  • 117
    Electronic Resource
    Electronic Resource
    Detection of hydrogen atoms in SiH4–H2 radio-frequency plasmas using two-photon laser-induced fluorescence (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 710-715 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Two-photon laser-induced fluorescence spectroscopy is used to detect ground-state atomic hydrogen in highly diluted SiH4–H2 radio-frequency discharges currently used for microcrystalline silicon thin film deposition. Along with the fluorescence coming from the hydrogen atoms created in the discharge, additional atoms arising from photodissociation of silicon containing species at 205 nm are observed. This parasitic effect is identified as resulting mainly from the disilane molecules formed in the plasma. Hydrogen atoms created in the plasma and originating from the photodissociation are discriminated by a spectral analysis of the laser-induced fluorescence line profile and relative densities are deduced. Some results on the hydrogen atom and disilane concentrations as functions of the silane dilution, radio-frequency power, gas pressure, and gas temperature are given to illustrate the potentiality of such a diagnostic in SiH4–H2 discharges containing up to 6% of silane. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1486033
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  • 118
    Electronic Resource
    Electronic Resource
    Laser ionization and radio frequency sustainment of high-pressure seeded plasmas (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 698-709 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The feasibility of using a photoionized, low-ionization potential organic seed gas to initiate a high pressure plasma discharge is examined and compared to radio frequency breakdown of high pressure argon alone. The seed gas, tetrakis(dimethylamino)ethylene, which has an ionization potential of 6.1 eV is ionized by an ultraviolet laser through 6.4 eV photon absorption, and forms a plasma column inside a vacuum chamber. The plasma absorbs additional power through inductive coupling of 13.56 MHz helical antenna radio frequency wave fields to the plasma through electron acceleration, ionization, and collisional damping. Laser initiation of 2–6 mTorr of the seed gas in 1–150 Torr of argon is accomplished and produces steady-state line-average plasma densities of ne(approximate)4×1012 cm−3 in a volume of 300 cm3. The two-body recombination coefficient of the organic seed gas and its optimum partial pressure when mixed with argon are experimentally determined and analyzed. Particle loss and power requirements for maintaining the discharge are evaluated by examining ionization, diffusion, and recombination processes. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1487905
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  • 119
    Electronic Resource
    Electronic Resource
    Harmonic content of electron-impact source functions in inductively coupled plasmas using an "on-the-fly" Monte Carlo technique (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 736-748 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electron temperatures in low-pressure (〈10s mTorr) inductively coupled plasma (ICP) reactors operating at 10s MHz do not significantly vary during the radio frequency (rf) cycle. There can be, however, considerable modulation of electron-impact source functions having high-threshold energies due to modulation of the tail of the electron energy distributions (EEDs). In many instances, it is convenient to use cycle-averaged values for these quantities in models due to the computational burden of computing and storing spatial and time-dependent EEDs. In this paper an "on-the-fly" (OTF) Monte Carlo technique is described to address these time-dependent plasma parameters. The OTF method directly computes moments of the EEDs during advancement of the trajectories of the pseudoparticles, thereby reducing computational complexities. The method can also be used to directly calculate the harmonic components of excitation, which can subsequently be used to reconstruct the time-dependent source functions. The OTF technique was incorporated into a two-dimensional plasma equipment model to investigate the time dependence of electron-impact source functions in low-pressure ICP systems. We found that even harmonics dominated the source functions for high-threshold processes, and that the harmonic content decreased with increasing frequency and increased with increasing pressure. We also observed axial pulses of excitation and increasing harmonic content at low pressures which are attributed to nonlinear Lorentz force acceleration and nonlocal transport. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1487455
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  • 120
    Electronic Resource
    Electronic Resource
    Plasma characterization during laser ablation of graphite in nitrogen for the growth of fullerene-like CNx films (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 724-735 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Chemistry, energy, and spatial distributions of species in carbon–nitrogen plasma plumes were investigated to define plasma conditions for growth of carbon nitride CNx films with a fullerene-like structure. Plumes were generated by ablation of graphite using a 248 nm excimer laser in the presence of low-pressure nitrogen. The plumes were investigated using element specific imaging, time-of-flight experiments, fluorescence spectroscopy, and molecular vibration sequence analyses. Studies showed the importance of plume/substrate interaction in causing secondary excitation phenomena. For N2 pressures within the 5–50 mTorr range, plasmas at the substrate vicinity were found to consist mostly of atomic carbon, CN and C2 molecules. Kinetic energies were calculated within 10–20 eV for mono atomic carbon, 30–55 eV for CN, and 20–40 eV for C2. Excited CN and C2 molecules were generated by laser ablation and by collisions of the plume with the substrate surface. Their vibrational energies were strongly influenced by nitrogen pressure and time after a laser pulse. For pressures below 30 mTorr, vibrational energy was as high as 4.0 eV at 2–4 μs for CN and 2.5 eV at 8–10 μs for C2. This low pressure was suggested for the growth of fullerene-like CNx films based on correlations between plasma parameters and film composition and bonding. Synthesis of the fullerene-like structure required high molecular temperatures at the condensation surface. High concentrations of CN radicals in the plasma promoted nitrogen incorporation into the films. Correlations among CNx film composition/bonding, excitation maximums, and kinetic/vibrational energies of atomic carbon, CN and C2 species located near the condensation surface are discussed. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1481972
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  • 121
    Electronic Resource
    Electronic Resource
    Optical modeling of a-Si:H solar cells deposited on textured glass/SnO2 substrates (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 749-755 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this article we determine descriptive scattering parameters—haze and angular distribution functions—of scattered light for textured glass/SnO2 Asahi U-type substrates. These scattering parameters are input parameters of our optical model that enables us to analyze multilayer optical systems with rough interfaces. The scalar scattering theory is used to calculate the haze parameters of all internal rough interfaces in the a-Si:H solar cells deposited on the glass/SnO2 substrates. In the equations of the scalar scattering theory the correction functions are introduced in order to match the calculations with the measurements of the haze parameters of the substrates. The angular distribution functions of the substrates are applied to the rough internal interfaces. Using these scattering parameters we investigate the optical behavior of a-Si:H solar cells with different intrinsic layer thicknesses deposited on the textured glass/SnO2 substrates with different roughnesses. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1487910
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    Effect of hydrogen and oxygen on stainless steel nitriding (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 764-770 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The influence of hydrogen and oxygen on stainless steel implanted by nitrogen low-energy ions is systematically studied. It is shown that hydrogen intervenes moderately in the process only when the oxygen partial pressure in the deposition chamber is relatively high. For very low-oxygen partial pressures, the energetic nitrogen molecules impinging on the substrate sputter the thin oxide layer formed on the substrate. This allows the growing of a rich nitrogen layer beneath the surface, improving the diffusing of the implanted atom deeper in the bulk material. For higher-oxygen partial pressures, the sputtering is ineffective, and an oxide layer partially covers the surface even in the presence of hydrogen. The maximum depth penetration of nitrogen depends on the degree of oxygen coverage, which is fairly well described by a Langmuir absorption isothermal. Hardness depth profiling is consistent with the existence of a diffusion barrier formed by the oxygen absorbed on the surface. In order to understand the role of hydrogen on the nitriding process, samples preimplanted with hydrogen were subsequently treated with nitrogen and the hardness depth profiling analyzed. These results may provide a clue about the practical consequences of oxygen and hydrogen on the nitriding process. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1483893
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    In situ study of void growth kinetics in electroplated Cu lines (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1803-1810 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An in situ electromigration apparatus was used to study the kinetics of void growth in unpassivated, electropolated copper damascene lines. Voids were observed to grow by consuming grains in a stepwise fashion, either by grain thinning or by an edge displacement mechanism. Surface diffusion was found to be the primary diffusion path for void growth. In addition, grain boundaries provided a secondary path for copper diffusion in polycrystalline structures and nucleation sites for void growth in bamboo structures. Void growth rate was measured as a function of sample temperature and linewidth using a scanning electron microscope. An electromigration activation energy of 0.9±0.1 eV was determined for the copper voiding process. The effect of linewidth on void growth rate was also investigated and found to be negligible, consistent with a surface-diffusion dominated model for void growth. The in situ apparatus also made it possible to directly correlate changes in electrical resistance with physical changes taking place in the test structures. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1492871
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    Ion-beam doping of silver in amorphous As2S3 thin films (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1821-1824 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Double layers of metallic Ag/amorphous (a-)As2S3 on silica substrates were irradiated with 300 keV He+ ions to examine doping of Ag+ into a-As2S3 by dense electronic excitation. The irradiating ions passed through the double layers and came to rest in the silica substrates. Thus, energy deposition from energetic He+ ions into the double layers was completely almost due to electronic processes (99.4%). Ionized silver found to diffuse into a-As2S3 as a result of electronic excitation by ion-beam irradiation. Rutherford backscattering spectroscopy revealed that the highest concentration of silver doped into a-As2S3 was 35 at. %. When the resulting Ag-doped a-As2S3 was illuminated by band gap light, photo-surface-deposition of metallic silver particles, which was not observed for Ag photo-doped specimens, was observed. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1492862
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  • 125
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    Optical response of one-dimensional (Si/SiO2)m photonic crystals (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1816-1820 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: One-dimensional photonic crystals made of (Si/SiO2)m multilayers with m=2,...8 have been grown on SiO2 4-in. wafers by repeated polysilicon low-pressure chemical vapor deposition, oxidation, and wet etching steps. The poly-Si and SiO2 layers were about 220 and 660 nm thick, respectively, thus realizing λ/4 distributed Bragg reflectors. Spectroscopic ellipsometry in the 1.4–5 eV range was used to determine the dielectric function of poly-Si and the actual layer thicknesses, as well as to check the structural and compositional homogeneity of the structures. In order to measure the photonic crystal properties, specular reflectance and transmittance measurements were performed from 0.2 to 6 eV at different angles of incidence θ≤50° and for transverse electric and transverse magnetic polarizations. The stop-bands characteristic of Bragg reflector multilayers appear up to the fifth order and become more pronounced with increasing m, reaching almost complete rejection for m=4 periods. The experimental spectra were fitted by the transfer-matrix method, both versus θ and m. Moreover, the experimental stop bands of the finite multilayers matched the calculated photonic band gaps of an infinite one-dimensional photonic crystal very well. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1492866
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    Crystal growth and characterization of the cubic semiconductor Cu2SnSe4 (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1811-1815 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: X-ray powder diffraction study of the p-type semiconductor Cu2SnSe4 shows that this material crystallizes in the cubic structure, space group F43m, with unit cell parameter a=5.6846(3) Å. The temperature variation of the hole concentration between 120 and 300 K, obtained from the Hall effect and electrical resistivity measurements, is due to the thermal activation of an acceptor level with ionization energy of about 0.02 eV. The temperature variation of the hole mobility is explained by considering the scattering of charge carriers by ionized impurities and acoustic phonons. From this analysis, the density-of-states effective mass of the holes is estimated to be about 0.8 me, me being the free electron effective mass. From the optical absorption spectra, the fundamental absorption edge is found to be direct. The value of the lowest energy gap and the spin-orbit splitting were estimated to be about 0.35 and 0.20 eV, respectively. The temperature dependence of the magnetization measurements shows that Cu2SnSe4 is paramagnetic, indicating that most of the copper atoms have the divalent charge state. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1492018
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    Influence of growth temperature on properties of zirconium dioxide films grown by atomic layer deposition (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1833-1840 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: ZrO2 films were grown by atomic layer deposition from ZrCl4 and H2O or a mixture of H2O and H2O2 on Si(100) substrates in the temperature range of 180–600 °C. The films were evaluated in the as-deposited state, in order to follow the effect of deposition temperature on the film quality. The rate of crystal growth increased and the content of residual impurities decreased with increasing temperature. The zirconium-to-oxygen atomic ratio, determined by ion-beam analysis, corresponded to the stoichiometric dioxide regardless of the growth temperature. The effective permittivity of ZrO2 in Al/ZrO2/Si capacitor structures increased from 13–15 in the films grown at 180 °C to 19 in the films grown at 300–600 °C, measured at 100 kHz. The permittivity was relatively high in the crystallized films, compared to the amorphous ones, but rather insensitive to the crystal structure. The permittivity was higher in the films grown using water. The leakage current density tended to be lower and the breakdown field higher in the films grown using hydrogen peroxide. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1493657
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  • 128
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    Submillimeter-wave Fourier transform spectroscopy of biological macromolecules (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 6105-6113 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this article we report experimental results on Fourier-transform infrared spectroscopy of deoxyribonucleic acid (DNA) macromolecules and related biological materials in the submillimeter range (i.e., ∼10–500 cm−1). Film samples made from commercial DNA fibers, polyadenylic acid potassium salt, and cellular agents such as the spore form of Bacillus subtillis have been prepared and measured. A broad series of measurements carried out in the low frequency region (10–50 cm−1) with a higher resolution of 0.2 cm−1 revealed fine features—multiple dielectric resonances in the submillimeter-wave spectra obtained from DNA samples. These long-wave absorption features are shown to be intrinsic properties of biological materials determined by phonon modes. The emphasis is on reproducibility of experimental spectra and on receiving reliable results. The effects of differences in sample preparation, including sample geometry, orientation, and aging are studied and separated from the phonon effects that determine the fine structure of transmission spectra. A direct comparison of spectra between different DNA samples reveals a large number of modes and a reasonable level of sequence-specific uniqueness. A theoretical study of two double helical DNA fragments has applied a normal mode analysis to predict spectra in the far infrared. Most of the modes determined by long-distance interactions are at frequencies below 220 cm−1, with the density higher than one mode per cm−1, which is approximately what was observed experimentally. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1466878
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  • 129
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    Competitive effects of grooves and photoalignment on nematic liquid-crystal alignment using azobenzene polymer (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1841-1844 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Effect of an anisotropic photoalignment layer and microgrooves on nematic liquid-crystal (LC) alignment was quantitatively examined using azobenzene polymer thin film with surface relief grating (SRG) of about 1 μm pitch. The SRG with various modulation depths was treated with polarized light irradiation to align molecules at 45° from the groove. Nematic LC molecules, 4′-n-pentyl-4-cyanobiphenyl, orient to the photoaligned direction on the SRG being shallower than 200 nm. The orientation rather sharply deviates from the photoaligned direction toward the groove direction with increasing grating depth into the deeper region than 200 nm and finally becomes parallel to the grooves on the SRG of 400 nm deep. This behavior is successfully simulated by the consideration of anisotropic surface interaction and an elastic energy of LCs. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1493658
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    Electrical damage of an ultrathin Si oxynitride layer induced by scanning tunneling spectroscopy (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1850-1857 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ultrathin Si oxynitride layers were examined by using scanning tunneling microscopy (STM) and spectroscopy (STS). These techniques revealed that a structural change from an intrinsic defect (Si–Si bond) to a damaged structure (Si cluster) takes place under conventional STM/STS conditions. Comparison of the damaged structures formed in the oxynitride with those in the oxide indicated that nitrogen atoms suppress the expansion of the damaged regions. It was also found that nitrogen incorporation enhances both the defect density and the atomic-scale roughness at the oxynitride/Si interface. We suggested that this degradation is related to a local strain produced by the N≡Si3 structures at the oxynitride/Si interface. On the contrary, a normal oxynitride structure had a higher resistance to an electrical stress than an intrinsic defect, but, when the constant electrical stress was applied, the normal oxynitride structure was also damaged. This damage proceeds in two steps: creation of charge traps, and then formation of Si cluster. From these STM/STS results, we proposed that the electrical breakdown of the conventional gate-oxide film proceeds as a four-step process: (1) formation of Si clusters by the damage of intrinsic defects, (2) creation of traps in the normal structure, (3) formation of Si clusters in the normal structure, and (4) complete local breakdown when the Si clusters become connected. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1492865
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    Substrate bias dependence of Raman spectra for TiN films deposited by filtered cathodic vacuum arc (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1845-1849 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Raman spectroscopy was used to characterize TiN films deposited by using an off-plane double bend filtered cathodic vacuum arc technique. The influence of substrate bias on the Raman spectra was systematically studied. Four peaks at 235, 320, 440, and 570 cm−1, related to transverse acoustic (TA), longitudinal acoustic (LA), second-order acoustic (2A), and transverse optical (TO) modes of TiN, respectively, were observed in the Raman spectra of TiN films. The intensity of all four peaks and the area fraction as well as the full width at half maximum (FWHM) of the TO peak increase drastically with increasing substrate bias, reaching a maximum at −100 V, and then decrease greatly. However, the area fraction of TA, LA, and 2A peaks, the FWHM of TA and 2A peaks, as well as the frequency of all four peaks decrease rapidly with increasing substrate bias to −100 V, and then increase greatly. At a bias above −200 V, only a slight change in the Raman spectra of TiN films were observed. The change in the N/Ti ratio is the main reason for the evolution in the Raman spectra of TiN films with increasing substrate bias. The internal stress and the crystal size play only a minor role in the Raman spectra of TiN films in the present study. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1491588
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    Silicon–on–insulator waveguide photodetector with Ge/Si self-assembled islands (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1858-1861 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated a silicon-based near-infrared photodetector using a waveguide with strong optical confinement. The high-difference index waveguide is obtained with a silicon–on–insulator substrate. The optically active region consists of self-assembled Ge/Si islands embedded in a p-i-n junction. The Ge/Si islands grown by high-pressure chemical-vapor deposition exhibit a broad photoluminescence and electroluminescence which are resonant around 1.5 μm. The photoluminescence and electroluminescence energies are correlated to the island size and to the island composition using a six-band k⋅p calculation. The spectral responsivity of the detectors is measured in a front facet coupling geometry with a broadband source and with semiconductor laser diodes. For a 0 V applied bias, responsivities of 25 and 0.25 mA/W are measured at room temperature at 1.3 and 1.55 μm, respectively. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1493656
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    Structural characterization of Ni–Al (111) interface by surface x-ray absorption spectroscopy (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1862-1867 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The evolution of the Ni/Al(111) interface has been studied in situ by x-ray absorption spectroscopy at the Ni–K edge. Ni films were deposited on bulk Al(111) with thickness ranging from 2 monolayers (ML) up to 30 ML. The aim was to determine the diffusion length of Ni and the phases that have formed. Ni diffused spontaneously at room temperature to a depth that we estimated to be of the order of 11 ML. The structure of Ni/Al(111) mixed interface has been characterized by x-ray absorption spectroscopy. With respect to previous studies on Al(110) the first phase formed on Al(111) is Al3Ni2-like instead of AlNi-like. Accordingly to previous observations, an AlNi3 phase forms on top of Al3Ni2 after the deposition of the first few monolayers. We propose that the pure Ni growth observed after deposition of 11 ML is due to the presence of the AlNi3 aluminide that acts as a diffusion barrier preventing deeper Ni penetration into Al at room temperature. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1493652
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    Dependence of luminescence efficiency on dopant concentration and sintering temperature in the erbium-doped Ba0.7Sr0.3TiO3 thin films (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1868-1872 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We found the dependence of luminescence efficiency on Er3+ concentration and sintering temperature in the Er-doped Ba0.7Sr0.3TiO3 (BST) thin films is governed by crystallinity and ion–ion interaction. X-ray diffraction and Raman studies of the sol-gel prepared samples show that the BST polycrystalline phase occurred when the sintering temperature reaches 700 °C, whereas, it becomes worse for temperature above 700 °C resulting from phase separation and the Er3+ concentration exceeding 3 mol % due to charge compensation mechanism. The observed green emission reaches maximum at sintering temperature 700 °C and 3 mol % Er3+ ions concentration. We also showed the Er dopant does not affect the dielectric property of BST thin films in C–V measurement and the Ba0.7Sr0.3TiO3 films doped with Er3+ ions may have potential use for electroluminescence devices. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1492870
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    Erratum: "Largely tunable midinfrared (8–12 μm) difference frequency generation in isotropic semiconductors" [J. Appl. Phys. 91, 2550 (2002)] (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 6212-6212 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1470664
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  • 136
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    Transmission spectroscopy of photonic crystal based waveguides with resonant cavities (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 4791-4794 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photonic crystal waveguides including resonant cavities have been fabricated and investigated by transmission spectroscopy. The waveguides consist of two missing rows in a triangular lattice of air holes in a GaAs/AlGaAs slab–waveguide structure. The mirrors of the cavities are formed by adding two rows of holes perpendicular to the guiding direction inside the waveguide. The spectrally broad photoluminescence of an InAs quantum dot layer in the heterostructure is used to probe the transmission. Depending on the resonator size, characteristic resonant peaks are observed in the transmission spectra. Finite difference time domain calculations of the transmission of the investigated structures show good agreement with experimental data. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1454199
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    Interdiffusion-based optimal quantum-well profile shaping for unipolar quantum-fountain lasers (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 4801-4805 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A method is described for the design and realization of quantum-well (QW) structures optimized in respect to gain in optically pumped intersubband lasers. It relies on finding the optimal smooth potential (QW profile) by employing supersymmetric quantum mechanics, and then using the simulated annealing method to design a suitable QW structure with a small number of layers of different composition, such that it delivers the closest approximate to the optimal smooth profile after the interdiffusion process. This route towards achieving optimal QW profiles should be much easier to apply than a direct modulation of material composition at time of growing the structure. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1464208
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    Electrical and optical properties of beryllium-implanted Mg-doped GaN (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1881-1887 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We investigated the electrical and optical characteristics of beryllium implanted Mg-doped GaN materials. The Mg-doped GaN samples were grown by metalorganic chemical vapor deposition system and implanted with Be ions at two different energies of 50 and 150 keV and two different doses of about 1013 and 1014 cm−2. The implanted samples were subsequently rapidly thermal annealed at 900, 1000, and 1100 °C for various periods. The annealed samples showed an increase of hole concentration by three orders of magnitude from nonimplanted value of 5.5×1016 to 8.1×1019 cm−3 as obtained by Hall measurement. The high hole concentration samples also showed low specific resistance ohmic contact of about 10−3 Ω cm2 and 10−6 Ω cm2 using Ni/Au and Ni/Pd/Au metallization, respectively, without any further annealing process. It is also found from the temperature dependent photoluminescence that the activation energy of Mg dopants of the Be implanted samples has an estimated value of about 170 meV, which is nearly 30% lower than the as-grown samples of about 250 meV. The crystal quality and surface morphology of the Be implanted samples measured by x-ray diffraction and atomic force microscopy show no obvious degradation in the crystal quality and surface morphology. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1494110
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    Microstructure study of amorphous vanadium oxide thin films using raman spectroscopy (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1893-1897 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Microstructural changes of amorphous V2O5 films with lithium intercalation are studied using Raman-scattering measurements. The Raman spectra of as-deposited films show two broad peaks around at 520 and 650 cm−1, due to the stretching modes of the V3–O and V2–O bonds, respectively, and a relatively sharp peak at 1027 cm−1 due to the V5+(Double Bond)O stretching mode of terminal oxygen atoms. In addition, there is a peak at 932 cm−1 that we attribute to the V4+(Double Bond)O bonds. Comparison of the Raman spectra of V2O5 films with different oxygen deficiencies confirms this assignment. This Raman peak due to the stretching mode of the V4+(Double Bond)O bonds develops and shifts toward lower frequencies with increasing lithium concentration. Comparison to results from gasochromic hydrogen insertion indicates that the 932 cm−1 Raman peak is not a result of vibrations which involve Li or H atoms. We propose that the V4+(Double Bond)O bonds are created by two different mechanisms: a direct conversion from V5+(Double Bond)O bonds and the breaking of the single oxygen bonds involving V4+ ions. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1495074
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    Characterization of Mg doped GaN by positron annihilation spectroscopy (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1898-1901 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Metalorganic vapor-phase epitaxially grown GaN films have been studied using beam positron annihilation spectroscopy. Positron lifetime and Doppler broadening of annihilation radiation measurements indicate that defects, probably Ga vacancies, are reduced in concentration when films are doped with Mg, as previously observed by other workers. In lightly doped films a homogeneous layer with a minimum defect concentration is present from just below the surface, to a depth of around 0.1 μm. For heavily doped films, there is evidence of a further substantial decrease in the defect concentration following an anneal to 900 °C. The effects of impurities and defects are discussed. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1492858
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    Morphological study of aluminum tris(8-hydroxyquinoline) thin films using infrared and Raman spectroscopy (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1902-1905 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present comprehensive Raman spectra for thin films of Alq3, annealed at various temperatures up to 300 °C, over the range of 70–1800 cm−1. These spectra give strong evidence for structural rearrangement of thin films of Alq3 upon annealing at temperatures above 200 °C. Needle like crystals are observed to grow in the films and confirmed to be comprised of the α-Alq3 polymorph using the low energy Raman spectra. Furthermore, no evidence of the fac isomer or thermal interconversion between the mer and fac isomers of Alq3 was observed in either the infrared or Raman spectra of the thin films or powder. These results may have implications for the long-term efficiencies of organic light emitting diodes incorporating thin films of Alq3. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1495527
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    Thermally induced modifications on bonding configuration and density of defects of plasma deposited SiOx:H films (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1906-1913 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The bonding configuration, hydrogen evolution, and defect content of rapid thermally annealed (RTA) SiOx:H films of different compositions were studied. Infrared absorption measurements showed that all the hydrogen present in the films is lost at annealing temperatures below 600 °C without any change in the oxygen to silicon ratio of the films. The activation energy of the hydrogen release is in the 0.21–0.41 eV range independently of film composition, suggesting that the process occurs via network bond reactions. For annealing temperatures higher than 700 °C, a change in the Si–O–Si stretching wave number from the initial unannealed value to the 1070–1080 cm−1 range was promoted, independently of the initial film composition. Electron spin resonance measurements showed that all the films contain two type of bulk paramagnetic defects: the E′ center (•Si(Triple Bond)O3) and the silicon dangling bond center (•Si(Triple Bond)Si3). The RTA process promotes a general decrease of defect concentration for annealing temperatures below 400 °C. At higher temperatures, E′ center disappears, and the •Si(Triple Bond)Si3 center increases its concentration up to the 1017–1018 cm−3 range. This suggests that the RTA at higher temperatures promotes the formation of a high-quality, almost defect-free, SiO2 matrix in which highly defective Si nanocrystals are also formed, where the •Si(Triple Bond)Si3 centers are located. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1495068
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  • 143
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    SiO2–TiO2 interfaces studied by ellipsometry and x-ray photoemission spectroscopy (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1922-1928 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present an in situ study of the formation of the interfaces between TiO2 and SiO2 evaporated thin films using spectroscopic ellipsometry and x-ray photoemission spectroscopy (XPS). The growth of TiO2 on SiO2 was studied previously, but the reverse case has not received much attention up to now. In this article, we show that a common description is valid for both interfaces, which are formed by crosslinking Ti–O–Si bonds. We show also that the growth of TiO2 on SiO2 begins with an amorphous interface layer even when growth occurs at 400 °C. The interface is sharp, a few angstroms, as determined by angular XPS; when SiO2 grows on TiO2, the interface is thicker, about 10 Å. Roughness and interdiffusion play roles in interface formation and their role will be discussed. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1494843
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  • 144
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    Investigation of the effect of high-temperature annealing on stability of ultrathin Al2O3 films on Si(001) (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1914-1921 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We investigated the stability of a uniform and stoichiometric 0.6-nm-thick Al2O3 film on a Si(001) surface during high-temperature annealing in ultrahigh vacuum (UHV), under low oxygen pressure (2×10−6, 5×10−6, and 2×10−5 Torr O2), and under high oxygen pressure (5×10−5 Torr O2) conditions. UHV annealing of the Al2O3/Si(001) system at 900 °C drastically degraded the Al2O3 film quality and caused atomic-scale roughness at the Al2O3/Si(001) interface. Voids formed in the oxide film as annealing progressed. A low oxygen pressure ambient during annealing, while more or less maintaining the film stoichiometry, caused atomic-scale roughness at the interface. A high oxygen pressure ambient during annealing maintained the film stoichiometry and thickness. However, this processing condition led to the formation of interfacial Si oxide, which caused substantial SiO volatilization and etching of the Si substrate at the Al2O3/Si(001) interface, thereby inducing nanometer-scale roughness at the interface. These results indicate that high-temperature processing imposes a limitation in controlling the composition of ultrathin Al2O3 films and maintaining the abruptness of the Al2O3/Si(001) interface on an atomic scale. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1495066
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  • 145
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    Analysis of interfacial silicates and silicides formed by annealing ultrathin Hf on SiO2: Effect of Hf/SiO2 thickness ratio (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1929-1935 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The annealing of two different ultrathin Hf/SiO2 stacks, i.e., Hf rich (1.7 ML/0.3 nm) and SiO2 rich (1 ML/1 nm) is investigated in situ in an ultrahigh vacuum (UHV) by using scanning tunneling microscopy and x-ray photoelectron spectroscopy. To describe the interface structure formed in practical high-k processes, this approach conjectures the effects of underlying SiO2 on the stability of metal–silicon and metal–oxygen bondings, which would subsequently determine the interfacial phases. The annealing of these film stacks causes silicate formation, but the relative thickness ratio between Hf and SiO2 is found to greatly affect a phase stability of interfacial silicates in a high-temperature (≥780 °C) regime. As the underlying SiO2 thickens, the Hf–Si bondings are expected to be replaced with Hf–O–Si (silicate) bonding units, even at room temperature deposition in an UHV. In the Hf-rich stack (Hf–Si bonding dominant), phase separation into silicides was observed at a relatively low temperature (∼780 °C) compared with a SiO2-rich one (Hf–O–Si bonding dominant) where silicidation occurs above 900 °C. Irrespective of the thickness ratio between Hf/SiO2, above 900 °C, two types of crystalline silicides, i.e., facetbars (metallic) and platelets (semiconducting), were observed and these silicides were also identified to be oxygen-free phases by analyzing their atomic structures. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1494846
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  • 146
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    Structural stability and electrical properties of Sr2FeMoO6 under high pressure (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1942-1944 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The structural stability and electrical properties of Sr2FeMoO6 under high pressure at room temperature have been studied using energy dispersive x-ray diffraction with synchrotron radiation and resistance and capacitance measurements. The x-ray diffraction results show that the structure of Sr2FeMoO6 remains stable up to 40 GPa. The equation of state of Sr2FeMoO6 is obtained from the V/V0–P relationship. The bulk modulus B0 and its first-order derivative B0′ of Sr2FeMoO6 were calculated based on the Birch–Murnaghan equation. The electrical resistance undergoes a metallic transition at about 2.1 GPa. The metallic transition may be caused by a change in the electronic structure induced by high pressure. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1496119
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  • 147
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    Directional diffusion and void formation at a Si (001) bonded wafer interface (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1945-1949 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Low-temperature hydrophobic bonding is an enabling technology allowing the fabrication of device structures. Current research into improvement of hydrophobic bonding has focused on the elimination of thermally generated voids. It has been observed that a regular grid etched into the bonding interface can eliminate the thermally generated voids. By manipulation of patterns etched into the bond interface, it was possible to ascertain that the diffusion of interfacial gasses that form the thermally generated voids is enhanced along the 〈110〉 directions. This is shown by an analysis of the void density at various locations in relation to the etched trenches at the bonded interface. Void density between trenches is shown to be 12% of the void density near trenches but nto along a 〈110〉 direction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1491590
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  • 148
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    Visible thermal emission from sub-band-gap laser excited cerium dioxide particles (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1936-1941 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Cerium dioxide particles excited in air with sub-band-gap radiation emit very broad radiation in the visible spectrum above a threshold intensity that decreases with increasing ambient temperature. Concomitant with this emission is the near disappearance of the Stokes and anti-Stokes Raman scattering peaks. Both phenomena are reversible in air up to just above threshold, and are seen for nanoparticles and several-micron-diameter particles with particle diameter comparable to or smaller than the laser focus. Temperature estimates using the Stokes/anti-Stokes scattering intensity ratio suggest there is laser heating due to small intragap absorption and possible nonlinear processes, given the very slow thermal conduction. The broad emission in this loose powder may well be due to thermal emission, on the basis of spectral fitting of the high-energy part of the spectrum to a blackbody radiator at ∼1200–1400 °C, although luminescence from a new phase is a possibility. The sudden decrease in Raman scattering and increase in emission in air are consistent with a transition to a new, possibly luminescent, phase, as is the continued disappearance of the Raman peaks in forming gas when the laser power is reduced below the upstroke threshold. Oxygen point defects and their complexes may play an important role in many of these processes. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1494130
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  • 149
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    Temperature and pressure dependences of the Mn2+ and donor–acceptor emissions in ZnS:Mn2+ nanoparticles (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1950-1955 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Temperature and pressure dependent measurements have been performed on 3.5 nm ZnS:Mn2+ nanoparticles. As temperature increases, the donor–acceptor (DA) emission of ZnS:Mn2+ nanoparticles at 440 nm shifts to longer wavelengths while the Mn2+ emission (4T1–6A1) shifts to shorter wavelengths. Both the DA and Mn2+ emission intensities decrease with temperature with the intensity decrease of the DA emission being much more pronounced. The intensity decreases are fit well with the theory of thermal quenching. As pressure increases, the Mn2+ emission shifts to longer wavelengths while the DA emission wavelength remains almost constant. The pressure coefficient of the DA emission in ZnS:Mn2+ nanoparticles is approximately −3.2 meV/GPa, which is significantly smaller than that measured for bulk materials. The relatively weak pressure dependence of the DA emission is attributed to the increase of the binding energies and the localization of the defect wave functions in nanoparticles. The pressure coefficient of Mn2+ emission in ZnS:Mn2+ nanoparticles is roughly −34.3 meV/GPa, consistent with crystal field theory. The results indicate that the energy transfer from the ZnS host to Mn2+ ions is mainly from the recombination of carriers localized at Mn2+ ions. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1495070
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  • 150
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    Reflective liquid-crystal display using an in-plane-switching super-twisted nematic cell (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1956-1959 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Two in-plane-switching (IPS) super-twisted nematic (STN) cells are proposed for reflective liquid-crystal displays. The IPS 180°-STN cell exhibits a normally black display with a relatively low-operating voltage, fast response time, and wide viewing angle. Potential applications for large screen reflective displays are foreseeable. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1496127
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  • 151
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    Effects of slight misorientation of GaN templates on molecular-beam-epitaxy growth of ZnO (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1960-1963 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Both the growth mechanism and material properties of ZnO epilayers are found to be strongly dependent on slight misorientation of GaN templates. The observation by in situ reflection high-energy electron diffraction and atomic force microscopy reveals that the growth mode changes from a three-dimensional to a two-dimensional growth mechanism, as the misorientation of GaN templates is varied from [0001] just to 0.2 degree toward the a axis. However, ZnO grows under a three-dimensional mode for misorientation toward the m axis. The observed changes in the growth mechanism are discussed in terms of the different surface migration length along the m and a axis, which is caused by the different surface atomic arrangement along the a and m axis. With an increase in the misorientation angle from 0 to 0.2° toward the a axis, the linewidth of (0002) x-ray rocking curve shows a dramatic narrowing from 1768 to 277 arcsec, while the photoluminescence intensity of exciton emission shows a remarkable enhancement by more than one order of magnitude. Such improvement in material properties can be ascribed to the observed change of the growth mode from three- to two-dimensional growth. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1493648
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  • 152
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    Thermopower enhancement in misfit cobaltites (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1964-1967 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The isovalent substitution of Ca2+ for Sr2+ substitution in the recently discovered misfit cobaltite [Pb0.7Co0.3Sr2O3] [CoO2]1.79 has been investigated for its very attractive thermopower properties. Starting from the pure Sr cobaltite with a thermopower S value at 300 K in the range from 100 to 130 μV K−1, it is found that the calcium substitution enhances the thermopower value up to +165 μV K−1 for the pure calcium phase, [Pb0.4Co0.6Ca2O3] [CoO2]1.61. Since these thermoelectric materials are studied for the high T applications, it should be pointed out that this S improvement induced by chemical substitution is even more pronounced for T(very-much-greater-than)300 K with S700 K=+210 μV K−1. This beneficial effect is interpreted in the light of the clear modification in the geometry of CoO2 layers which could play a role on the cobalt electronic configurations. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1494114
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  • 153
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    Deep levels in semi-insulating InP obtained by annealing under iron phosphide ambiance (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1968-1970 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Deep levels in semi-insulating (SI) InP obtained by annealing in iron phosphide (IP) ambiance have been characterized by optical transient current spectroscopy (OTCS). Compared with the OTCS result of the SI InP prepared by annealing in pure phosphorus (PP) ambiance, the IP SI InP presents only two traps with activation energies of 0.20 and 0.63 eV, respectively. The results suggest that the diffusion of Fe-atoms suppresses the formation of a few defects in the IP SI InP. The nature of deep levels in the IP and PP SI InP has been discussed on the basis of these results. The relation between material property and defects in those SI InP has also been revealed. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1491026
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  • 154
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    Transient simulations of a resonant tunneling diode (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1987-1994 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Stationary and transient simulations of a resonant tunneling diode in the ballistic regime are presented. The simulated model consists in a set of Schrödinger equations for the wave functions coupled to the Poisson equation for the electrostatic interaction. The Schrödinger equations are applied with open boundary conditions that model continuous injection of electrons from reservoirs. Automatic resonance detection enables reduction of the number of Schrödinger equations to be solved. A Gummel type scheme is used to treat the Schrödinger–Poisson coupling in order to accelerate the convergence. Stationary I–V characteristics are computed and the transient regime between two stationary states is simulated. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1494127
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  • 155
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    Superfast fronts of impact ionization in initially unbiased layered semiconductor structures (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1971-1980 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A mode of impact ionization breakdown of a p–n junction is suggested: We demonstrate that when a sufficiently sharp voltage ramp is applied in reverse direction to an initially unbiased equilibrium p+–n–n+ structure, after some delay the system will reach a high conductivity state via the propagation of a superfast impact ionization front. The front travels towards the anode with a velocity vf several times larger than the saturated drift velocity of electrons vs leaving a dense electron–hole plasma behind. The excitation of the superfast front corresponds to the transition from the common avalanche breakdown of a semiconductor structure to a collective mode of streamer-like breakdown. We propose that similar fronts can be excited not in layered structures but in plain bulk samples without p–n junctions. Our numerical simulations apply to a Si structure with typical thickness of W∼100 μm switched in series with a load R∼100 Ω, with a voltage ramp of A〉1012 V/s applied to the whole system. Our simulations show that first there is a delay of about 1 ns during which the voltage reaches a value of several kilovolts. Then, as the front is triggered, the voltage abruptly breaks down to several hundreds of volts within ∼100 ps. This provides a voltage ramp of up to ∼2×1013 V/s hence up to 10 times sharper than the externally applied ramp. We unravel the source of initial carriers which trigger the front, explain the origin of the time delay in triggering the front, and we identify the mechanism of front propagation. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1494113
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  • 156
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    Anisotropic random resistor networks: A model for piezoresistive response of thick-film resistors (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1981-1986 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Considerable evidence suggests that thick-film resistors are close to a metal–insulator transition and that tunneling processes between metallic grains are the main source of resistance. We consider as a minimal model for description of transport properties in thick-film resistors a percolative resistor network, with conducting elements governed by tunneling. For both oriented and randomly oriented networks, we show that the piezoresistive response to an applied strain is model dependent when the system is far away from the percolation thresold, while in the critical region it acquires universal properties. In particular close to the metal–insulator transition, the piezoresistive anisotropy shows a power law behavior. Within this region, there exists a simple and universal relation between the conductance and the piezoresistive anisotropy, which could be experimentally tested by common cantilever bar measurements of thick-film resistors. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1495067
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  • 157
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    Electrical conductivity of Wesgo AL995 alumina under fast electron irradiation in a high voltage electron microscope (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1995-1999 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electrical conductivity of a 295-μm-thick Wesgo AL995 alumina has been measured before and during 1 MeV electron irradiation in a dc electric field of 300 kV/m at temperatures up to 723 K. The difference between the activation energies before (0.49±0.02 eV) and during (0.19±0.06 eV) irradiation indicates a substantial impact of irradiation on the conductivity of Wesgo AL995 alumina. The electrical conductivity of Wesgo AL995 alumina is lower by approximately 2 orders of magnitude than its requirement for the magnetic coils in the international thermonuclear experimental reactor (ITER). Thermal disruption may not impact on Wesgo AL995 alumina insulating material in ITER because of the absence of thermally stimulated conductivity peaks in it. Although no substantial bulk degradation is observed under irradiation up to a fluence of 7.0×1022 e/m2 (7.97×10−5 dpa) at 723 K, surface degradation is detected that could limit the application of Wesgo AL995 in ITER as a potential insulator. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1494845
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  • 158
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    Conduction-induced oxidation of silicon on silver metaphosphate glass (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 2166-2171 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: dc biasing of silicon-anoded silver metaphosphate glass with a pulse train enabled us to follow the process of conduction-induced oxidation of silicon. Biasing with 1000 or 500 V/cm at or below 140 °C induced formation of a dielectric oxide having capacitance of around 10−7 F cm−2. From a large relaxation time of polarization involved, e.g., 10−4 s at 140 °C, it is suggested that the oxide is not the genuine silicon dioxide. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1494849
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  • 159
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    Subpicosecond laser ablation of dental enamel (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 2153-2158 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Laser ablation of dental enamel with subpicosecond laser pulses has been studied over the intensity range of (0.1–1.4)×1014 W/cm2 using 95 and 150 fs pulses at a pulse repetition rate of 1 kHz. The experimentally determined ablation threshold of 2.2±0.1 J/cm2 was in good agreement with theoretical predictions based on an electrostatic ablation model. The ablation rate increased linearly with the laser fluence for up to 15 times the ablation threshold. The absence of collateral damage was observed using optical and scanning electron microscopy. Pulpal temperature measurements showed an increase of about 10 °C during the 200 s course of ablation. However, air cooling at a rate of 5 l/min resulted in the intrapulpal temperature being maintained below the pulpal damage threshhold of 5.5 °C. The material removal rates for subpicosecond precision laser ablation of dental enamel are compared with other techniques. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1495896
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  • 160
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    A gas-spring system for optimizing loudspeakers in thermoacoustic refrigerators (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 2159-2165 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Moving-coil loudspeakers are appropriate drivers for thermoacoustic refrigeration. They are cheap, commercially available, compact, light, and can be adapted to meet specific requirements. This paper deals with the optimization of loudspeakers for thermoacoustic refrigeration. Using an electrical model that describes the refrigerator, it is concluded that the electroacoustic efficiency can be maximized over a wider frequency range by matching the mechanical resonance frequency of the driver to the acoustic resonance frequency of the resonator. A gas-spring system is introduced as a practical tool to shift the mechanical resonance frequency of the driver. An electroacoustic efficiency of 35% is obtained when the mechanical resonance frequency of the driver and the acoustic resonance frequency are equal. Additionally, the efficiency is constant over a relatively wide frequency range. This has advantages for thermoacoustic refrigeration. During cool-down, the operating acoustic frequency decreases so that the refrigerator will keep near the optimum performance. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1492867
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  • 161
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    H2S gas sensing mechanism of SnO2 films with ultrathin CuO dotted islands (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 2172-2180 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: H2S gas interaction mechanisms of sputtered SnO2 and SnO2–CuO bilayer sensors with a varying distribution of the Cu catalyst on SnO2 are studied using Pt interdigital electrodes within the sensing film. Sensitivity to H2S gas is investigated in the range 20–1200 ppm. Changes induced on the surface, the SnO2–CuO interface, and the internal bulk region of the sensing SnO2 film upon exposure to H2S have been analyzed to explain the increasing sensitivity of three different sensors SnO2, SnO2–CuO, and SnO2 with CuO islands. SnO2 film covered with 0.6 mm diameter ultrathin (∼10 nm) CuO dots is found to exhibit a high sensitivity of 7.3×103 at a low operating temperature of 150 °C. A response speed of 14 s for 20 ppm of H2S, and a fast recovery time of 118 s in flowing air have been measured. The presence of ultrathin CuO dotted islands allow effective removal of adsorbed oxygen from the uncovered SnO2 surface due to spillover of hydrogen dissociated from the H2S–CuO interaction, and the spillover mechanism is sensed through the observed fast response characteristics, and the high sensitivity of the SnO2–CuO-dot sensor. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1490154
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  • 162
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    Electron emission from N-doped homoepitaxially grown diamond (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 2194-2197 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electron emission properties of N-doped homoepitaxially grown diamond have been measured and discussed in order to clarify the electron emission mechanism by excluding the effects of polycrystallinity. As a result, N-doped homoepitaxially grown diamond exhibits extremely low threshold electron emission even from extremely flat smooth surfaces without grain boundaries. This result strongly implies that the low threshold electron emission from N-doped diamond should be caused by the resistance of the film rather than by high β whatever the underlying mechanism is. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1494842
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  • 163
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    Growth and interfacial studies of conjugated oligomer films on Si and SiO2 substrates (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 4213-4219 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The growth of [2,5-bis(4-styryl)styryl] 1,4-dioctyloxybenzene, (Ooct-OPV5) oligomer films on Si (100)-(2×1) and Si (111)-(7×7) reconstructed surfaces as well as on a SiO2 film over a Si (100) wafer was studied by x-ray photoelectron spectroscopy (XPS). Ooct-OPV5 resembles poly (p-phenylenevinylene) (PPV), a polymer that is widely used in organic light emitting diodes. High purity oligomer films of up to 18 nm thickness were prepared on the clean substrates by stepwise evaporation in ultrahigh vacuum conditions and a layerwise growth of films was observed on all substrates. The electronic structure of the oligomer interface with n-doped Si (111) was investigated by combined x ray and ultraviolet photoelectron spectroscopies (XPS) and (UPS). The C 1s XPS peak of the bulk oligomer consisted of three components, all associated with oligomer functional groups at binding energies 285.05, 285.75, and 287.15 eV, respectively. During growth, both C 1s and O 1s peaks in the film exhibited an upward BE shift of 0.45±0.05 eV, from which the total band bending at the interface was evaluated. The depletion region in the organic film during the interface was found to be ∼90 Å thick. The UP spectra of the oligomeric film exhibited characteristic peaks that resemble those of PPV, and the oligomer work function was found to be 4.00±0.05 eV. The interface between the two materials in contact proved to be nonreactive and no detectable electric dipole was observed. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1456251
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  • 164
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    Laser beam induced currents in polycrystalline silicon thin films prepared by interference laser crystallization (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 4220-4228 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Polycrystalline silicon layers are prepared by interference laser crystallization (ILC) in the superlateral growth regime. To characterize their microscopic photoelectrical properties, light beam induced current (LBIC) is used, employing a focused laser beam for local generation of photocarriers in the layers with spatial resolution of (approximate)0.4 μm. The results are correlated with surface morphology obtained by atomic force microscopy. In the single pulse ILC, the temperature profiles are optimized by changing the proportion of interfering beam intensities. The typical grains are of triangular shape, with a length of 1.5 μm and width 〈0.5 μm. The photocurrent response is dominated by variations in the sample thickness. In the multiple pulse ILC, thin films with grains of quadratic shape and of size exceeding 5 μm are obtained by shifting the sample through an interference pattern, thus taking advantage of lateral epitaxial regrowth. Here, by use of a lock–in, LBIC can detect position and local electronic properties of individual grain boundaries. Grain boundaries are clearly identified by 180° shifts of the photocurrent phase close to maxima of photocurrent amplitude. The photocurrent is attributed to local fields at grain boundaries. These fields extend about 1.4 μm into the grains. The barrier height at the boundary is about 110 mV. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1458058
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  • 165
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    Microstructural and electronic properties of Ni thin films grown on p-InP (100) substrates (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 4238-4241 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ion beam-assisted deposition of Ni on p-InP (100) at room temperature was performed in order to produce Ni thin films with high quality and Ni/p-InP (100) heterostructures with abrupt heterointerfaces. An atomic force microscopy image showed that the root mean square of the average surface roughness of the Ni film was 21.3 Å, and x-ray diffraction and transmission electron microscopy (TEM) measurements show that Ni film layers grown on InP (100) substrates were polycrystalline. Auger electron spectroscopy and TEM measurements showed that Ni films grown on p-InP (100) substrates at room temperature had no significant interdiffusion problems. The work function of the Ni thin film was determined from the secondary electron emission coefficients obtained with a focused ion beam. These results provide important information on the microstructural and electronic properties for Ni thin films grown on p-InP (100) substrates at room temperature. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1454196
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  • 166
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    Intrinsic noise of a micromechanical displacement detector based on the radio-frequency single-electron transistor (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 4249-4255 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We investigate the intrinsic noise of a micromechanical displacement detector based on the radio-frequency single-electron transistor (rf-SET). Using the noise analysis of a SET by Korotkov [Phy. Rev. B 49, 10381 (1994)] as our starting point, we determine the spectral density of the displacement noise due to the tunneling current shot noise. The resulting mechanical displacement noise decreases in inverse proportion to the increasing gate voltage. In contrast, the displacement noise due to the fluctuating SET island charge increases approximately linearly with increasing gate voltage. Taking into account both of these noise sources results in an optimum gate voltage value for the lowest displacement noise and hence best sensitivity. We show that a displacement sensitivity of about 10−4 Å and a force sensitivity of about 10−16 N are predicted for a micron-sized cantilever with a realizable resonant frequency 100 MHz and quality factor Q∼104. Such sensitivities would allow the detection of quantum squeezing in the mechanical motion of the micromechanical cantilever and the detection of single-spin magnetic resonance in magnetic resonance force microscopy. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1453494
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  • 167
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    IrO2-based thick-film resistors (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 4261-4266 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: IrO2-based thick-film resistors were prepared and their microstructure/electrical property relationship was studied as a function of the firing temperature Tf and composition. The resistor microstructure exhibits a notable change, from a strongly segregated structure for Tf=750 °C, to a quasihomogeneous one when the firing temperature increases to Tf=850 °C. Likewise, a substantial change is observed in the sheet resistance (Rs) dependence on the volume fraction (v) of the conductive phase. For resistors prepared at Tf=750 °C the percolation power law Rs(approximate)(v−vc)−t (where vc and t are the critical volume fraction and exponent, respectively) is observed, while samples fired at Tf≥850 °C follow the relation ln Rs(approximate)a(v−v0) where a and v0 are proper constants. In addition, the slope of plot a is affected by the firing temperature Tf as well as by the measuring temperature at T〈50 K. Very high temperature coefficients of resistance are measured at cryogenic temperatures. The longitudinal gauge factor values are in the range from 3 to 12.4 according to the resistor composition and firing temperature, with the highest values in samples fired at 950 °C with sheet resistance in the range from 104 to 107 Ω/(square, open). © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1454223
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  • 168
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    Development of a three-dimensional numerical model of grain boundaries in highly doped polycrystalline silicon and applications to solar cells (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 4271-4274 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have developed a three-dimensional numerical model of grain boundaries to simulate the electrical properties of polycrystalline silicon with doping densities larger than approximately 5×1017 cm−3. We show that three-dimensional effects play an important role in quantifying the minority-carrier properties of polycrystalline silicon. Our simulations reproduce the open-circuit voltage of a wide range of published experiments on thin-film silicon p-n junction solar cells, choosing a velocity parameter for recombination at the grain boundaries, S, in the order of 105–106 cm/s. The simulations indicate that, although S has been reduced by one order of magnitude over the last two decades, improvements in the open-circuit voltage have mainly been achieved by increasing the grain size. A few options are proposed to further reduce S. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1456962
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  • 169
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    Difference in hydrogen sensitivity between Pt and Pd field-effect devices (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 4275-4280 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An explanation is given for the large differences in the hydrogen sensitivity in air observed for gas sensitive field-effect devices with palladium and platinum gates, respectively. It is demonstrated that this difference is mainly due to a difference in the hydroxyl formation rate between the two metals. The water production rates are, however, almost the same for the two metals. The considerably smaller sensitivity of platinum devices in air is then due to the much lower steady-state hydrogen atom concentration on the platinum surface compared with the palladium surface. This leads to a smaller coverage of hydrogen atoms at the metal–oxide interface and thus a smaller response of the device at a given hydrogen concentration in air. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1448874
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  • 170
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    Scattering mechanisms and electronic behavior in transparent conducting ZnxIn2Ox+3 indium–zinc oxide thin films (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 4291-4297 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin films of ZnxIn2Ox+3 (x=2, 3, 4, 5, 7, 9, 11, 13, and 15) were grown by pulsed laser deposition and their electronic properties characterized. Through resistivity, Hall mobility and carrier concentration measurements as a function of temperature, we found that whatever the composition, these films behave as n-type degenerate semiconductors exhibiting a metal-like behavior. Transport properties are driven by two types of electronic scattering, namely ionized impurities (oxygen vacancies) at low temperature and optical phonons at high temperature. Modeling of optical transmittance spectra in the visible-infrared region yields two different trends among the different compositions: for (x=2, 3, 4, 5, 7, and 9) values the electronic behavior can be described by applying the single Drude model on a plasma of nearly free carriers, whereas for zinc-rich (x=11, 13, and 15) compounds a supplementary Lorentz oscillator is necessary to simulate the spectroscopic data, revealing the presence of bound optically active electrons. Good agreement is found in every case between the experimental Hall mobility and the "optical" mobility calculated from relaxation time and effective mass fitted parameters. We show that the mobility drop can be explained primarily by a drastic increase in the effective mass for the highest x values. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1445496
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  • 171
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    Channel formation in organic field-effect transistors (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 4312-4318 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Results of two-dimensional electrostatic modeling of organic field-effect transistors, focusing on the formation of the conductive channel, are reported. The effect on channel formation of the choice of the source and drain contact metal is investigated for both top- and bottom-contact device structures. High-work-function metal (e.g., gold) source and drain contacts produce a conducting p-type region near these contacts. In contrast, low-work-function metal source and drain contacts (e.g., magnesium) lead to depleted regions. In the center of the device, between the source and drain contacts, the channel carrier density at a fixed gate bias is determined by the work function of the gate contact material, and is essentially independent of the metal used to form the source and drain contacts. The principal difference between top- and bottom-contact structures is the spatial variation of the charge density in the vicinity of the source and drain contacts. The channel carrier density for a fixed gate bias (and gate contact material) between the source and drain electrodes is essentially the same for the two structures. Finally, the dependence of the transistor threshold voltage on the gate contact metal work function and the device implications of the spatial variation of the induced charge density are discussed. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1453509
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  • 172
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    Gap state distribution in amorphous hydrogenated silicon carbide films deduced from photothermal deflection spectroscopy (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 4319-4325 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The density of gap states distribution in silicon (Si) rich hydrogenated amorphous silicon carbide (a-Si1−xCx:H) films with varying carbon (C) fraction (x) is investigated by the photothermal deflection spectroscopy (PDS). The films are grown using the Electron Cyclotron Resonance Chemical Vapor Deposition (ECR-CVD) technique. By using different methane-to-silane gas flow ratios, a-Si1−xCx:H with x ranging from 0 to 0.36 are obtained. A deconvolution procedure is performed based on a proposed DOS model for these Si rich a-Si1−xCx:H. Good fits between the simulated and experimental spectra are achieved, thus rendering support to the model proposed. Deduction of the DOS enables us to obtain various parameters, including the optical gap and the valence band tail width. The fitted mobility gap Eg is found to be well correlated to the Tauc gap Etauc and E04 gap deduced from the optical absorption spectra. A correlation is also seen between the fitted valence band tail width Evu, the Urbach energy Eu and the defect density. All these parameters are seen to increase with C alloying. A shift in the defect energy level in the midgap with increasing C incorporation is observed, together with a broadening of the defect distribution and a stronger correlation between the defect bands, which can be accounted for in terms of the influence of C dangling bonds on the deep defect density distribution. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1448888
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  • 173
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    Potential fluctuations in metal–oxide–semiconductor field-effect transistors generated by random impurities in the depletion layer (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 4326-4334 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied the magnitude and length scale of potential fluctuations in the channel of metal–oxide–semiconductor field-effect transistors due to the random positions of ionized impurities in the depletion layer. These fluctuations effect the threshold voltage of deep submicron devices, impede their integration, and reduce yield and reliability. Our simple, analytic results complement numerical, atomistic simulations. The calculations are based on a model introduced by Brews to study fluctuations due to charges in the oxide. We find a typical standard deviation of 70 mV in the potential below threshold, where the channel is empty, falling to 40 mV above threshold due to screening by carriers in the channel. These figures can be reduced by a lightly doped epitaxial layer of a few nm thickness. The correlation function decays exponentially in an empty channel with a length scale of 9 nm, which screening by carriers reduces to about 5 nm. These calculations of the random potential provide a guide to fluctuations of the threshold voltage between devices because the length of the critical region in a well-scaled transistor near threshold is comparable to the correlation length of the fluctuations. The results agree reasonably well with atomistic simulations but detailed comparison is difficult because half of the total standard deviation comes from impurities within 1 nm of the silicon–oxide interface, which is a single layer of the grid used in the simulations. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1450031
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  • 174
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    Physical phenomena in a coplanar macroscopic plasma display cell. II. Comparisons between experiments and models (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 1000-1007 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Measurements of infrared and visible emission in a macroscopic discharge cell similar to a plasma display panel (PDP) cell are analyzed using a two-dimensional fluid model of the discharge. The comparisons between experiments and models show a good qualitative agreement but the plasma spreading velocity above the cathode surface is much faster in the experiments. We find that including photoemission (in a simplified way) in the model considerably increases the agreement between experiments and models. With a well-chosen photoemission coefficient, the model reproduces the trends observed in the experiments when the gas mixture (between 2% and 10% of xenon in neon) or the applied voltage is changed. The influence of photoemission on the current rise time and on the velocity of plasma spreading above the dielectric surfaces is more important in the macrocell than in a similar (same dimension × pressure) PDP cell because resonant photon transport does not follow the similarity laws. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1425426
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  • 175
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    Ion and neutral energy flux distributions to the cathode in glow discharges in Ar/Ne and Xe/Ne mixtures (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 1026-1030 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The work presented in the article is a study of the heavy particle (ion and neutral) energy flux distributions to the cathode in conditions typical of discharges used for luminous signs for advertising ("neon" signs). The purpose of this work is to evaluate the effect of the gas mixture on the sputtering of the cathode. We have combined two models for this study: a hybrid model of the electrical properties of the cathode region of a glow discharge and a Monte Carlo simulation of the heavy particle trajectories. Using known sputtering yields for Ne, Ar, and Xe on iron cathodes, we estimate the sputtered atom flux for mixtures of Ar/Ne and Xe/Ne as a function of the percent neon in the mixture. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1430891
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  • 176
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    Dispersion relation in plasmas generated by a sheath-helix antenna (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 1031-1039 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A theoretical model of the plasmas generated by a sheath-helix antenna is developed for axisymmetric perturbations. The system configuration consists of a cylindrical plasma column inside a dielectric tube of radius Rc. The eigenvalue equation is obtained and the eigenfunction is identified as the Bessel function J0(x) of the first kind of order zero. The radial wave numbers ξ and η for the eigenfunction are described in terms of the rf frequency and plasma density. A full dispersion relation is analytically obtained, including influence of the finite plasma size, antenna effects, the electron inertia, and ion mass contributions. It is shown from the dispersion relation that the radial mode number ξ approaches infinity at the lower-hybrid frequency, exhibiting a resonance condition. Meanwhile, the radial wave number η approaches 3.83/Rc at the lower-hybrid frequency. A cross-sectional view of the light emission in experiment indicates that the helicon-plasma density at the lower-hybrid frequency has a hollow profile. The azimuthal component Eθ(r) of the perturbed electric field observed experimentally is very similar to the theoretical model of J1(3.83r/Rc) at the lower-hybrid frequency. The emission peak coincides with the radial location of the strongest electric-field intensity. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1429773
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    Characterization of CrBN films deposited by ion beam assisted deposition (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 1040-1045 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This article reports on the growth and analysis of CrBN nanocrystalline materials using an ion beam assisted deposition process. In addition, this article addresses the utilization of spectroscopic ellipsometry for in situ analysis of ternary nitrides. Coatings, with a total thickness of 1.5±0.2 μm, were deposited at low temperatures (〈200 °C) on silicon substrates using ion beam assisted deposition. These coatings were characterized postdeposition using x-ray diffraction (XRD), atomic force microscopy (AFM), x-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), visible-light spectroscopic ellipsometry (VIS-SE), infrared spectroscopic ellipsometry (IR-SE), and nanoindentation. The primary phases in the films were investigated using XRD. The surface morphology and nanocrystalline nature of the coatings (grain size of 5–7 nm) were deduced using AFM. The elemental composition and phase composition of the samples were determined from XPS and AES measurements and were subsequently deduced from the analysis of the VIS-SE data, and these correlated well. XPS, AES, and IR-SE revealed the crystal structure of the BN phase in the ternary compounds. The correlation of the results from these various techniques indicates that in situ SE may be a potential technique to control the growth of ternary nitride coatings in the future. The mechanical properties of the coatings were evaluated using nanohardness testing. The hardness and elastic modulus were measured to be 19–22 GPa and 250–270 GPa, respectively. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1426243
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  • 178
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    Epitaxial SnO2 thin films grown on (1¯012) sapphire by femtosecond pulsed laser deposition (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 1060-1065 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An ultrafast (100 fs) Ti sapphire laser (780 nm) was used for the deposition of SnO2 thin films. The laser-induced plasma generated from the SnO2 target was characterized by optical emission spectroscopy and electrostatic energy analysis. It was found that the ionic versus excited-neutral component ratio in the plasma plume depends strongly on the amount of background oxygen introduced to the deposition chamber. Epitaxial SnO2 films with high quality and a very smooth surface were deposited on the (1¯012) sapphire substrate fabricated at 700 °C with an oxygen background pressure of ∼0.1 mTorr. The films are single crystalline with the rutile structure, resulting from the high similarity in oxygen octahedral configurations between the sapphire (1¯012) surface and the SnO2 (101) surface. Hall effect measurements showed that the electron mobility of the SnO2 film is lower than that of bulk single crystal SnO2, which is caused by the scattering of conduction electrons at the film surface, substrate/film interface, and crystal defects. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1426245
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  • 179
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    Ultrafast dynamics at a silicon surface detected with femtosecond transient reflecting grating spectroscopy (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 1074-1080 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The recently developed spectroscopic transient reflecting grating technique with a time resolution of 200 fs was applied to a silicon surface under the pump intensity of more than 1 mJ/cm2. This method provides information on excited free carrier dynamics and subsequent heat generation and diffusion selectively based on appropriate choice of probe wavelength. With regard to the thermal component, the temperature at the surface increased within several picoseconds and then decayed after about 300 ps. As the pump intensity was increased, the maximum temperature rise showed a nonlinear dependence on it, and also the temperature rise time became faster. The results led to the conclusion that the carrier dynamics causing a temperature rise at a silicon surface is dominated mainly by Auger recombination, not by the decay to a band edge under the high carrier density conditions. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1420769
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  • 180
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    General solution for the thermal wave scattering in fiber composites (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 1087-1098 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this article we present a general solution for the ac temperature field generated from a modulated heating in an opaque material containing a series of aligned subsurface cylinders. The model includes the multiple scattering effects suffered by the plane thermal wave, generated by a planar heat source, when interacting with the cylinders and with the sample surfaces. A series solution to the heat diffusion equation and a matrix formulation to solve the scattering coefficients are used. There are no restrictions on the cylinders number, on their size and position inside the material, nor on the thermal properties of cylinders and sample. For completeness the case of coated cylinders is also investigated. Numerical calculations for the case of nonconducting cylinders illustrate the effect of the multiple scattering of the incident thermal wave on the sample surface temperature. A specific case of interest of the model is its application to the thermal characterization and nondestructive evaluation of fiber reinforced composites. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1421633
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  • 181
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    Influence of strain-induced indium clustering on characteristics of InGaN/GaN multiple quantum wells with high indium composition (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 1104-1107 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the effect of strain-induced indium clustering on the emission properties of InGaN/GaN multiple quantum wells grown with high indium composition by metalorganic chemical vapor deposition. Indium clustering confirmed by high-resolution transmission electron microscopy results in the redshift of the emission peak and the increase of the integrated photoluminescence (PL) intensity. We found that strong carrier localization in indium clustering induces the increases of the activation energy of PL integrated intensity, the temperature independence of PL decay profiles, and the intensity fluctuation of the cathodoluminescence images. All these observations suggest structurally and optically that the improved emission properties in the InGaN/GaN multiple quantum well with high indium composition are associated with the localized states in the strain-induced indium cluster. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1427143
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  • 182
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    Quantitative evaluation of biaxial strain in epitaxial 3C-SiC layers on Si(100) substrates by Raman spectroscopy (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 1113-1117 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present experimentally determined biaxial strain coefficients for the longitudinal optical (LO) and transversal optical (TO) Raman lines in 3C-SiC. Suspended 3C-SiC membranes with a (100) texture are deflected by a variable pressure load on one side and the strain-induced shifts of the LO and TO Raman lines are measured while the strain is simultaneously calculated from the membrane deflection vs pressure. Using these results we measure the residual strain of 3C-SiC films grown on Si as a function of preparation conditions. The largest residual strain is found in thin samples which relaxes as film thickness increases to a value imposed by the different thermal expansion coefficients of 3C-SiC and Si. As the residual strain decreases and the film thickness increases, the Raman lines narrow indicating an improved crystalline quality. We also find a reduction of the residual strain with increasing growth rate. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1427408
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  • 183
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    Thermoelectric efficiency in graded indium-doped PbTe crystals (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1425-1430 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High efficiency thermoelectric conversion is achieved by using materials with a maximum figure of merit Z=S2σ/k, where S is the Seebeck coefficient, σ and k, the electrical and thermal conductivities, respectively. High quality homogeneous thermoelectric materials, based on PbTe crystals, usually display an elevated value of Z over a narrow temperature range. A maximal value of figure of merit Z, as a function of electron density, is attained only for one specific location of the Fermi level, EF, with respect to the conduction band edge, EC. In order to maintain this optimal Z value, namely, maintain a constant location of the Fermi level, the electron density, which is determined by the dopant concentration, must increase with increasing temperature. We present a method for the generation of a dopant (indium) concentration profile in n-type PbTe crystals that gives rise to a constant location of the Fermi level, and hence, to an optimal value of Z over a wide temperature range. The resulting functionally graded material, based on PbTe〈In〉, displays a practically constant value of the Seebeck coefficient, over the 50–600 °C temperature range. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1490152
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  • 184
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    Characterization of the hot electron distribution function using six moments (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 3869-3879 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The shape of the hot electron distribution function in semiconductor devices is insufficiently described using only the first four moments. We propose using six moments of the distribution function to obtain a more accurate description of hot carrier phenomena. An analytic expression for the symmetric part of the distribution function as a function of the even moments is given which shows good agreement with Monte Carlo data for both the bulk case and inside n+−n−n+ test structures. The influence of the band structure on the parameters of the distribution function is studied and proven to be of importance for an accurate description. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1450257
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  • 185
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    Effect of pseudomorphic stress on structure and transport properties of ultrathin GdBa2Cu3O7 films on (001) SrTiO3 and NdGaO3 (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 1265-1271 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We investigated the structure and transport properties of GdBa2Cu3O7 films on SrTiO3(001) and NdGaO3(001). We found that the films can be grown pseudomorphically up to at least 42 nm thickness on SrTiO3 whereas the critical thickness is less than 14 nm for films on NdGaO3. The carrier density of pseudomorphic films on SrTiO3 is tuned by the pseudomorphic stress field and films on SrTiO3 show higher T* and lower Tc compared to films of the same thickness on NdGaO3. For a 28 nm thick GdBa2Cu3O7 film on SrTiO3, the hole density per CuO2 plane is reduced to 0.12, compared to 0.16 for the optimally doped and stress-free RBa2Cu3O7. The measured temperature dependence of Jc can be understood and described by interface stress pinning. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1425440
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  • 186
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    Ion-beam processing effects on the thermal conductivity of n-GaN/sapphire (0001) (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 1277-1280 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have measured high spatial/depth resolution (2–3 μm) thermal conductivity (κ) at 300 K before and after plasma-induced effects on two series of n-GaN sapphire (0001) samples fabricated by hydride vapor phase epitaxy using scanning thermal microscopy. The sample thicknesses were 50±5 μm for one set and 25±5 μm for the second. The carrier concentrations were ∼8×1016 cm−3 and ∼1.5×1017 cm−3, respectively, as determined by Hall effect measurements. The thermal conductivity before treatment was similar to that previously reported for hydride vapor phase epitaxy material with comparable carrier concentration and thickness [D. I. Florescu et al., J. Appl. Phys. 88, 3295 (2000)]. Damage was induced by ion-beam processing the samples under constant Ar+ gas flow and pressure for a fixed period of time (5 min), with the dc bias voltage (Vdc) being the only variable processing parameter (125–500 V). The thermal conductivity near the surface, κ, was found to exhibit a linear decrease with Vdc in the investigated range after this procedure. A second process was then applied in order to remove some damage. In this case the samples were processed under a constant mixture of Cl2 and Ar+ gas flow and Vdc′ of 50 V. For the samples with Vdc in the range 125 V〈Vdc≤250 V, κ was found to be actually lower after the damage removal process. The minimum κ was found at 250 V. This is probably due to Ar+ beam channeling [O. Breitschadel et al., Appl. Phys. Lett. 76, 1899 (2000)], which has been reported on similar structures at this voltage. When the initial processing voltage was 250 V〈Vdc〈500 V, κ showed a tendency to recover somewhat. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1428798
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  • 187
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    Study on bias-enhanced nucleation of diamonds by simulating the time dependence of bias current (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 3934-3936 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The kinetics of bias-enhanced nucleation (BEN) of diamonds in microwave plasma-enhanced chemical vapor deposition were investigated. During a BEN step, the increase of bias current was proportional to the area covered by diamond nuclei. This result provided information regarding the kinetics of nucleation. Avrami's kinetics were carefully introduced to describe the time dependence of the bias current. Our analysis shows that the decrease of activation energy (0.08–0.18 eV) of atomic diffusion increased as the negative bias voltage is increased from −80 to −120 V. The mechanism of enhancement of atomic diffusion by ion bombardment in the incubation period was also presented. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1452780
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  • 188
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    Passivation-mediated growth of Co on Se, S and O rich GaAs surfaces: A potential approach to control interface crystallinity and magnetic continuity (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 3943-3945 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Passivation-mediated growth was used to control the interface crystalline order and the magnetic continuity in epitaxial Co films on several GaAs(001) surfaces. Using Se, S, and O passivated layers on GaAs before Co deposition, we observed a variety of interface structures depending on the substrate condition. With the help of transmission electron microscopy (TEM) images, we show that a perfect and well-ordered crystalline growth at the initial stage of deposition for Co/Se/GaAs ensures a better growth for thicker film. The magnetic properties of Co overlayers on all the substrates were studied by magnetic linear dichroism in angular distribution (MLDAD) in photoemission and found to be different depending on the film crystallinity. By combining the TEM and MLDAD results, we conclude that Co film on Se/GaAs, which has an ordered interface, is a good candidate for use as a spin filter from the viewpoint of spin-injection mechanism. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1452760
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  • 189
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    X-ray characterization of annealed iridium films (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 1149-1154 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The changes in the mechanical and structural properties of sputter-deposited iridium films are described as a function of annealing temperature from 673 to 1073 K. Glancing angle x-ray diffraction and x-ray reflectivity measurements indicated the growth of an IrO2 overlayer by annealing at 873 K. An increased annealing temperature of 1073 K led to the oxidation of the underlying iridium layer yielding a film comprising IrO2 (major) and Ir (minor) phases. Annealing the films at 873 and 1073 K also led to an increased surface roughness of the films. As-deposited as well as films annealed at 673 and 873 K exhibited tensile stresses along the normal to the plane in consideration. Annealing at 673 K and cooling within a tube furnace relaxed normal and shear stress present in as-deposited 20 nm Ir metal films. Slow cooling, formation of oxygen–iridium bonding, and increased roughness caused the preferential relaxation of the shear stresses for the film annealed at 873 K. The oscillations observed in the strain-sin2 ψ curve for the films annealed at 1073 K could be due to texture in the film and/or stress gradient across the thickness of the film. The residual stress has, therefore, not been evaluated for these films. X-ray photoelectron spectroscopic measurements on the iridium film annealed at 1073 K show that the film is oxygen rich at the surface and oxygen deficient near the substrate. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1429798
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  • 190
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    Vibrational properties and microstructure of reactively sputtered hydrogenated carbon nitrides (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 1155-1165 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The present study is focused on the vibrational and structural characterization of a set of disordered hydrogenated carbon nitride (a-CN:H) thin films grown by reactive sputtering. A comparative analysis of the experimental results as achieved by Raman and infrared (IR) spectroscopies is made. The disorder-induced features of IR and Raman spectra are discussed as well in light of the current assessment on the vibrational properties of carbon-based materials. Some differences between a-CN:H and nonnitrogenated a-C:H materials are evidenced and attributed to the effects of charge redistribution and bond polarization due to the presence of nitrogen. In order to justify such a hypothesis, the dielectric constant, the dynamic effective charge, and the IR cross section determined by the charge transfer effects are calculated and found to be in agreement with the corresponding experimental values. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1425424
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  • 191
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    Influence of strain relaxation on structural and optical characteristics of InGaN/GaN multiple quantum wells with high indium composition (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 1166-1170 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Influence of strain relaxation on structural and optical properties of the InGaN/GaN multiple quantum wells (MQWs) with high indium composition grown by metalorganic chemical vapor deposition was investigated. From photoluminescence and transmission electron microscopy (TEM), we found that within the MQWs, the formation of misfit dislocation affects the degradation of optical properties more than the formation of stacking faults. For the MQWs with indium composition above the critical indium composition on the formation of misfit dislocation, the position of the main emission peak is significantly affected by the increase of quantum well numbers compared to samples with indium composition below the critical indium composition. The origins of redshift by the increase of quantum well numbers is believed to be caused by the increase of indium segregation in the MQWs using high-resolution TEM and energy dispersive x-ray spectroscopy. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1429765
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  • 192
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    Soft magnetism of Fe–Co–N thin films with a Permalloy underlayer (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1477-1482 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A systematic investigation was carried out on the Fe–Co–N thin films with varying Permalloy underlayer thicknesses (in short Py(backward-slash)Fe–Co–N films), which show significantly improved magnetic softness when a very thin Permalloy underlayer is applied. The easy axis coercivities of the Py(backward-slash)Fe–Co–N films drop from 1.3 kA/m (16 Oe) to 640 A/m (8 Oe) with an appropriate Permalloy underlayer; and the corresponding hard axis coercivity drops from 320 A/m (4 Oe) to less than 80 A/m (1 Oe). The highest transverse permeability is observed in the Py(backward-slash)Fe–Co–N film with a Permalloy underlayer of 3.5 nm, which also shows the smallest dispersion angle α50 among the Py(backward-slash)Fe–Co–N films. The changes in the mean grain size, texture, and magnetostriction are determined to not be responsible for the observed magnetic softness in the Py(backward-slash)Fe–Co–N films. In contrast, a tantalum underlayer does not reduce the coercivities and dispersion angles in the Ta(backward-slash)Fe–Co–N films. Based on these results, an exchange-induced ripple reduction mechanism is proposed to explain the effects of the Permalloy underlayer on the Py(backward-slash)Fe–Co–N films. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1491017
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  • 193
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    Piezoelectric and strain properties of Ba(Ti1−xZrx)O3 ceramics (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1489-1493 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The polarization and strain behavior of Ba(Ti1−xZrx)O3 (x=0–0.3) ceramics are studied. The unipolar strain levels of ∼0.18% at 40 kV/cm and of ∼0.25% at ∼120 kV/cm with small hysteresis were obtained for the ceramics with 0.03≤x≤0.08. The remnant polarization is ∼13–18 μC/cm2 for 0.03≤x≤0.08 and below 2 μC/cm2 for 0.15≤x≤0.3 at room temperature. The electromechanical coupling coefficient K33=56.5% and the piezoelectric stain coefficient d33=236 pC/N were obtained for the ceramics with x=0.05. These results indicated that the Ba(Ti1−xZrx)O3 system is a promising lead-free high strain material for applications. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1487435
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  • 194
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    Coercivity enhancement above the Néel temperature of an antiferromagnet/ferromagnet bilayer (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1483-1488 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Single-crystal thin films of the antiferromagnet FeF2 have been used to exchange bias overlayers of Fe. An unexpected coercivity enhancement is observed at temperatures above the Néel temperature of the FeF2. This coercivity reaches a peak value of over 600 Oe close to the Néel temperature and persists to above 300 K. The coercivity is correlated with the growth of an anisotropy in the ferromagnet, the increase of the antiferromagnetic susceptibility and the increase of the ferromagnetic resonance linewidth. We argue that the growth of spin fluctuations in the antiferromagnet leads to an enhanced ferromagnetic anisotropy, and therefore coercivity, above the Néel temperature. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1491277
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  • 195
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    Piezo-, pyro-, ferroelectric, and dielectric properties of (Pb0.88Sm0.08)(Ti1−xMnx)O3/polyetherketoneketone 50/50 vol % ceramic/polymer composites (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1494-1499 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: (Pb0.88Sm0.08)(Ti1−xMnx)O3/polyetherketoneketone 50/50 vol % ceramic/polymer composite films were studied with regard to their piezo-, pyro-, ferroelectric, and dielectric properties. The dielectric relaxation reflects the interaction between the constituent phases. Appropriate values of the dielectric permittivity, remanent polarization, and piezoelectric coefficients were obtained in the same way as those of other ceramic/polymer composite films. However, the coercive field, the pyroelectric coefficient, the pyroelectric figure of merit, and the electromechanical coupling factor were lower and the mechanical losses were higher. These results are discussed taking into account the incorporation of Sm3+ and Mn4+ into the perovskite structure in the ceramic phase. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1490615
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  • 196
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    X-ray diffuse scattering of p-type porous silicon (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 2742-2752 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An x-ray diffuse scattering investigation of p-type porous silicon (PS) is reported. Synchrotron radiation and laboratory measurements of the x-ray diffuse scattering at small and large scattering wave-vector q values are presented. At small q values and for p−-type material, small isotropic crystallites of a few nanometers diameter are shown, whereas for p+-type material the main cylindrical crystallites are larger. At large q values the fine p+ PS structure is investigated and reveals the presence of small spherical crystallites around the main cylindrical crystallites. The elastic relaxation of silicon crystallites in the porous structure is also presented for oxidized and for as-formed samples, using reciprocal space maps. PS superlattice diffuse scattering is then observed. Finally, these results are discussed in relation to previous x-ray studies and other methods of structural observation. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1429791
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  • 197
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    Study of photoluminescence in lead tungstates doped with Pr3+, Sm3+, and Er3+ ions (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 2766-2768 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoluminescence (PL) in PbWO4 single crystals doped with Pr3+, Sm3+, and Er3+ ion, which were grown by the Czochralski method, was studied. By investigating the PL for incident radiation with wavelength of 325 nm (He–Cd Laser), the energy levels of the PL centers were found: The PL levels in the Pr doped single crystal are 3Po and 1D2, that in the Sm-doped one is 4G5/2, and those in the Er doped one are 2H11/2, 4S3/2, and 4F9/2. In conclusion, the characteristics of these single crystals are governed solely by those of the rare-earth dopants, not by the lead tungstate. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1436295
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  • 198
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    Monte Carlo calculation of electron drift characteristics and avalanche noise in bulk InAs (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 1331-1338 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Field dependent drift velocity results are presented for electron transport in bulk indium arsenide (InAs) material based on a Monte Carlo model, which includes an analytical treatment of band-to-band impact ionization. Avalanche multiplication and related excess noise factor (F) are computed as a function of device length and applied voltage. A decrease in F with increases in device length is obtained. The results suggest an inherent utility for InAs-based single-photon avalanche detectors, particularly around the 2 μm region of interest for atmospheric remote sensing applications. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1429771
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  • 199
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    Preparation and thermoelectric properties of CeFe4As12 (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 1344-1348 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The thermoelectric properties of CeFe4As12 have been measured. The compound was synthesized by reacting a powder mixture of CeAs2 and FeAs2 with As metal. The sample was characterized by both x-ray diffractometry and electron microprobe analysis. The Seebeck coefficient, electrical resistivity, Hall effect, and the thermal conductivity were measured between room temperature and about 900 K. The results indicate that CeFe4As12 possesses semimetallic behavior similar to that of CeFe4Sb12 with a room temperature electrical resistivity of 0.49 mΩ cm and a Seebeck coefficient of about 40 μV/K. The thermal conductivity of CeFe4As12 lies between that of CeFe4P12 and CeFe4Sb12 as may be expected from considerations of anionic mass and rattling effect of Ce atoms inside the skutterudite unit cell. A maximum thermoelectric figure of merit value of about 0.4 was obtained at 850 K for this compound. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1427141
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  • 200
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    Quasiparticle band structures of wurtzite and rock-salt ZnO (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 1339-1343 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Band structures of both wurtzite and rock-salt ZnO were investigated using the ab initio pseudopotential method with both local density approximation (LDA) and GW approximation. The error in approximating 3d electrons as core electrons was investigated for both LDA and quasiparticle calculations. The differences between the band structures obtained by the GW approximation and LDA were explained. The quasiparticle band structures were compared with experimental results. The spin–orbit splitting was calculated for both wurtzite and rock-salt ZnO with the LDA. The density of states was investigated with the GW approximation. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1424058
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