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  • 2000-2004  (40,356)
  • 1990-1994  (4)
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  • 2002  (40,356)
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  • 1
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Physics Letters B 294 (1992), S. 466-478 
    ISSN: 0370-2693
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Physics Letters B 317 (1993), S. 474-484 
    ISSN: 0370-2693
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 3
    Book
    Book
    Wien [u.a.] :Springer, ; 1.1977 - 16.2003; damit Ersch. eingest.
    Title: Computing : archives for informatics and numerical computation; Supplementum
    Publisher: Wien [u.a.] :Springer,
    Year of publication: 1977-2003
    Dates of Publication: 1.1977 - 16.2003; damit Ersch. eingest.
    Type of Medium: Book
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5840-5852 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this study, micro-Raman spectroscopy has been used to investigate the vibrational properties of laterally epitaxial overgrown (LEO) GaN. The LEO GaN films were grown by metal organic chemical vapor deposition on a 2 in. sapphire substrate with SiN mask. Photoluminescence and polarized Raman scattering measurements have been performed in the two regions of GaN growth (wing and window regions). Raman scattering results are consistent with the lateral growth of GaN in the overgrown region. We have observed second-order Raman scattering in the wing and window regions of GaN. The observations of longitudinal optical phonon plasmon modes in the overgrown region demonstrate that LEO GaN is doped. We have carried out micro-Raman mapping of the local strain and free carrier concentration in the LEO GaN. Anharmonicity due to temperature in LEO GaN has also been investigated. The anharmonicity was found to increase with increasing temperature, and such temperature-induced anharmonicity introduces changes in the linewidth and line center position of the Raman active phonons. The phonon lifetimes in GaN are estimated in the LEO region as well as in the coherently grown region (window region). © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5853-5857 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Microstructural observations of gallium arsenide single crystals irradiated with a few tens of MeV C60 incident clusters (fullerenes) were performed. Normal and grazing incidences were investigated. Similar to in the case of silicon and germanium, cylindrical amorphous tracks whose diameters vary as a function of the projectile energy were found. However, for a given energy of the clusters, the track diameters are slightly different from one material to another. Also depending on the fullerene, energy is the length of the amorphous cylinder that formed along the projectile's path. The recrystallization process under an electron beam during transmission electron microscopy observation was analyzed and a higher growth rate for gallium arsenide compared to that of germanium was seen. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5858-5866 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This article presents an analysis of the response of silicon carbide to high velocity impact. This includes a wide range of loading conditions that produce large strains, high strain rates, and high pressures. Experimental data from the literature are used to determine constants for the Johnson–Holmquist constitutive model for brittle materials (JH-1). It is possible to directly determine the strength and pressure response of the intact material from test data in the literature. After the ceramic has failed, however, there are not adequate experimental data to directly determine the response of the failed material. Instead, the response is inferred from a comparison of computational results to ballistic penetration test results. After the constants have been obtained for the JH-1 model, a wide range of computational results are compared to experimental data in the literature. Generally, the computational results are in good agreement with the experimental results. Included are computational results that model interface defeat, which occurs when a high velocity projectile impacts a ceramic target and then dwells on the surface of the ceramic with no significant penetration. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5867-5874 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The influence of ion-beam-produced lattice defects as well as H, B, C, N, O, and Si, introduced by ion implantation, on the luminescence properties of wurtzite GaN is studied by cathodoluminescence spectroscopy. Results indicate that intrinsic lattice defects produced by ion bombardment mainly act as nonradiative recombination centers and do not give rise to the yellow luminescence (YL) of GaN. Experimental data unequivocally shows that C is involved in the defect-impurity complex responsible for YL. In addition, C-related complexes appear to act as efficient nonradiative recombination centers. Implantation of H produces a broad luminescent peak which is slightly blueshifted with respect to the C-related YL band in the case of high excitation densities. The position of this H-related YL peak exhibits a blueshift with increasing excitation density. Based on this experimental data and results reported previously, the chemical origin of the YL band is discussed. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5875-5881 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: InGaAs strained quantum well (SQW) samples with lattice matched InGaAsP quaternary barriers are grown on GaAs substrates by metalorganic vapor phase epitaxy. These SQW samples are characterized using photoluminescence, photomodulated reflectance, surface photovoltage spectroscopy and high-resolution x-ray diffraction techniques. The results based on numerical calculations are used to identify the various transitions seen in the spectra. The effect of growth temperature on the indium content of the InGaAs SQW with lattice matched InGaAsP quaternary barriers is studied. Contrary to the reported higher value of indium incorporation in InGaAs SQW with GaAs (In-free) barriers when the growth is performed at low temperatures, we find that the indium content of the InGaAs SQW with InGaAsP (In-based) quaternary barriers decreases if the SQW is grown at lower growth temperatures. A possible explanation for this behavior is provided. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5882-5886 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: B1–NaCl-structure CrN(001) layers were grown on MgO(001) at 600 °C by ultrahigh vacuum reactive magnetron sputter deposition in pure N2 discharges. X-ray diffraction analyses establish the epitaxial relationship as cube-on-cube, (001)CrN(parallel)(001)MgO with [100]CrN(parallel)[100]MgO, while temperature-dependent measurements show that the previously reported phase transition to the orthorhombic Pnma structure is, due to epitaxial constraints, absent in our layers. The resistivity increases with decreasing temperature, from 0.028 Ω cm at 400 K to 271 Ω cm at 20 K, indicating semiconducting behavior with hopping conduction. Optical absorption is low (α〈2×104 cm−1) for photon energies below 0.7 eV and increases steeply at higher energies. In situ ultraviolet photoelectron spectra indicate that the density of states vanishes at the Fermi level. The overall results provide evidence for CrN exhibiting a Mott–Hubbard type band gap. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5887-5891 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a simple model for quantum well photodetectors for simultaneous middle infrared and near infrared or visible dual-band detection. We derive analytical formulas for the responsivity and detectivity as functions of the material and structural parameters. It is shown that the characteristics of near infrared and visible radiation detection can be sensitive to parameters of the hole transport, capture into quantum wells, and reflection from the electron emitting contact. We demonstrate that a properly designed photodetector can exhibit comparable performance for both middle infrared and near infrared (or visible) detection. The obtained results can be used to optimize the photodetector design and characteristics in both spectral ranges. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 11
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5892-5895 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We investigated through ab initio total energy calculations the interaction of arsenic impurities with the core of a 30° partial dislocation in silicon. It was found that when an arsenic atom sits in a crystalline position near the dislocation core, there is charge transfer from the arsenic towards the dislocation core. As a result, the arsenic becomes positively charged and the core negatively charged. The results indicate that the structural changes around the impurity are very small in both environments, namely, the crystal and the dislocation core. In this scenario, the interaction between arsenic and the core is essentially electrostatic, which eventually leads to arsenic segregation. The segregation energy was found to be as large as 0.5 eV/atom. Additionally, it was found that arsenic pairing inside the core is not energetically favorable. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5896-5901 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on inelastic electron tunneling spectroscopy of a tunneling metal–oxide–semiconductor (MOS) device over an extended energy range compared to previous results. We have clearly observed the vibrations of the hydrogen-passivated (111)Si Pb center in this extended energy range. The assignment of this mode has been confirmed by a comparison with infrared experiments. Capabilities and limitations of the technique to detect and observe molecular vibrations in tunneling MOS devices are discussed. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5902-5908 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the effect of rapid thermal annealing (RTA) on the photoluminescence (PL) properties of GaNxAs1−x/GaAs structures. In particular, a blueshift of the PL peak energy is observed when annealing the samples. The results are examined as a consequence of a RTA-induced nitrogen diffusion inside the GaNxAs1−x material rather than diffusion out of the alloy, which homogenizes initial nitrogen composition fluctuations. We propose a simple model that describes the RTA-induced blueshift of the low temperature PL peak energy. This model is in good agreement with experimental results and is consistent with recent studies in which lateral composition fluctuations in the GaNAs alloy were reported. © 2002 American Institute of Physics.
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  • 14
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5909-5914 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A quadratic dependence of the band gap energy on the alloy composition x was quantified for CuAl(SxSe1−x)2 films grown by low-pressure metalorganic vapor phase epitaxy, by means of photoreflectance and photoluminescence excitation spectroscopies. The bowing parameter for the A-exciton energy was estimated to be 0.20 eV. Several high-quality films grown on GaAs(001) substrates exhibited excitonic photoluminescence peaks in the blue to ultraviolet spectral ranges. The flow rate of the Al precursor was found to affect the incorporation ratio of S/Se, indicating that the Al–S compound plays a key role in controlling x. All films grown on GaAs(001) showed c(001) orientation. Conversely, the epitaxitial orientation of the films on GaP(001) changed from a(100) to c(001) with an increase in x. The critical value of x was around 0.5. The preferred orientations were explained by the natural selection rule under which the lattice strain in the epilayer is minimized. The residual strain in the 0.5-μm-thick epilayers on GaAs(001) was nearly constant for all x, although the lattice mismatch between the epilayer and the GaAs substrate varied from 0.62% to 5.39% with an increase in x. Consequently the strain was attributed to thermal stress. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 15
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 3556-3561 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The design and manufacture of diode lasers for gas analysis or multilayer thin-film optical devices used at low-temperature require the refractive index and the temperature coefficient of IV–VI compound over a significant temperature range. In this article, the refractive index and the absorption coefficient of Pb0.94Ge0.06Te thin film have been determined from transmission spectra measured at temperature between 80 and 300 K in the spectral range of 2.5–8.5 μm by fitting based on a Lorentz-oscillator model. It is found that the maximum refractive index occurs at 150 K, which corresponds to the structural phase transition from rocksalt to rhombohedrally distorted structure and reflects an increase of lattice polarizability. The value of the index of refraction is 5.350–6.000 in the spectral range of 4.0–8.5 μm for all measured temperatures, which reveals that Pb1−xGexTe is a highly refractive infrared material. The temperature coefficient of refractive index, dn/dT, is found to be −0.006–0.002 K−1 in the spectral range of 3.0–8.5 μm for all measured temperature. An empirical formula that fits the temperature coefficient in the spectral range of 4.0-8.5 μm is presented. The dependence of the transmission and absorption spectra on decreasing temperature can be explained by the modification of the energy-band structure due to rhombohedral distortions. The conclusion can be drawn that anomalies corresponding to the ferroelectric phase transition occur in both refractive index and absorption coefficient of Pb1−xGexTe alloy. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 16
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 3569-3578 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This article uses molecular dynamics simulation to investigate the role of Ar ions in the ion physical vapor deposition (IPVD) process for different Ar+-to-Cu+ ratios, and to analyze the influence of different Ar+-to-Cu+ ratios on the trench filling morphology. Also compared are the trench filling morphology observed for the IPVD process with that found in the conventional collimated magnetron deposition process. The molecular dynamics simulation includes a trench model and a deposition model, and uses the many-body, tight-binding potential method to represent the interatomic force acting among neutral atoms. The interatomic force acting between the ions and the neutral atoms is modeled by the pairwise Moliere potential method. The simulation indicates that the incident Ar ions influence the trench filling mechanisms in two significant ways; peeling of the cluster atoms, which promotes migration of the cluster atoms along the sidewall, and breaking of the bridge which forms when two clusters of atoms join. Both phenomena are beneficial since they promote a more complete filling of the trench. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 17
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 3750-3758 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: FeCoV/TiNx and FeCoV/Ti multilayers having tFeCoV=30–700 Å prepared by dc magnetron sputtering are investigated by x-ray diffraction, stress, and magnetization measurements. The x-ray diffraction data of the FeCoV/TiNx system show the presence of interstitial N atoms in the FeCoV layers due to reactive sputtering of Ti with nitrogen. The interstitial N causes an expansion of the FeCoV lattice in FeCoV/TiNx for small tFeCoV. However, for the samples with large tFeCoV, no lattice expansion is observed. In addition to the lattice expansion caused by the intake of N atoms, a change in the crystalline texture of FeCoV layers is also observed as indicated by the enhancement of the FeCoV(200) peaks. The magnetic hysteresis measurements on the samples show that the easy direction of magnetization lies in the plane of the layers. They further show that there are easy and hard axes of magnetization within the plane of the FeCoV layers. The stress anisotropy present in the plane of the samples induces a magnetic anisotropy through magnetostrictive effects leading to the formation of the in- plane easy axis. The hysteresis and stress measurements carried out on these samples clearly show the influence of N on the in-plane magnetic anisotropy. The magnetoelastic energy in the case of the FeCoV/TiNx system, calculated from the stress data and from the magnetization measurements as a function of tFeCoV is found to agree over a large range of thickness, whereas the curves deviate significantly for small layer thickness. This deviation may be due to the role of the FeCoVNx phase. Hysteresis measurements also show that the remanence is about 95% for all the samples of the FeCoV/TiNx system. In contrast, the coercivity increases linearly with increasing tFeCoV in this system. The coercivity of the FeCoV/Ti system is larger and increases more rapidly with tFeCoV, as compared with the FeCoV/TiNx system. This behavior is attributed to a smaller grain size in the FeCoV/TiNx system due to the reactive sputtering of the Ti layers. However, there is no significant influence of N on the saturation magnetization of both systems. © 2002 American Institute of Physics.
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  • 18
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 3764-3768 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The amorphous alloys Nd40Fe40Co5Al8B7, Nd57Fe20Co5Al10B8, and Nd57Fe20Cu5Al10B8 were prepared by copper mold casting, melt spinning, and mechanical alloying. Despite their similar x-ray diffraction patterns, samples display different magnetic and thermal behavior correlated with the method of preparation. The fully amorphous melt-spun ribbons exhibit relatively soft magnetic properties with coercivities (approximate)40 kA/m at room temperature and a Curie temperature (TC)(approximate)474 K. Apparently only the mold-cast cylinders of 3 mm diameter show hard magnetic behavior with a coercivity in the range of 258–270 kA/m (depending on composition) and have approximately the same TC as that of the melt-spun ribbons. An additional magnetic transition at 585 K due to the presence of Nd2Fe14B phase in the case of Nd40Fe40Co5Al8B7 cast rod has been observed. Heat treatment above crystallization temperature in as-cast Nd57Fe20Co5Al10B8 and Nd57Fe20Cu5Al10B8 samples destroys the hard magnetic properties. In contrast, mechanically alloyed amorphous samples are soft magnetic with maximum coercivity up to 11 kA/m but show an entirely different TC(approximate)680–740 K, which is rather characteristic of an Fe solid solution. The magnetic properties are discussed in terms of different local atomic environment and cluster sizes in amorphous samples prepared by different methods. © 2002 American Institute of Physics.
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  • 19
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 3769-3774 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The phase evolution, microstructure, and magnetic properties of Nd8Fe86B6−xCx (x=0, 2, 4, 5, 6) melt-spun ribbons were systematically studied as a function of C content. It was found that the addition of C decreases the glass-forming tendency of the as-spun ribbons significantly. A uniform nanoscale exchange coupled Nd2Fe14(BC)/α-Fe microstructure with an average grain size of 20–25 nm can be developed in the directly quenched ribbons with C contents up to 4 at. %. Further increase of C content to x=5 leads to, in the optimally quenched ribbons, the presence of an undesirable Nd2Fe17Cx phase in addition to the 2:14:1 and α-Fe phases, whereas the alloy ribbon containing 6 at. % C consists almost entirely of the soft magnetic Nd2Fe17Cx and α-Fe phases. Subsequent annealing induces a transformation of the 2:17:Cx phase to the 2:14:1 phase +α-Fe in the ribbons with x=5 and 6, resulting in the formation of a composite 2:14:1/α-Fe structure having relatively large crystallite sizes. Magnetic measurements revealed that, for the optimally processed samples, replacement of up to 4 at. % of B by C significantly increases the coercivity iHc, with only slight reduction in remanence Jr; an optimum coercivity of 542 kA/m was obtained in the Nd8Fe86B2C4 ribbon compared with 430 kA/m for the Nd8Fe86B6 ribbon. Excessive substitution of C (x〉4) causes a drastic deterioration of both iHc and Jr due to the microstructural coarsening. Moreover, the Curie temperature of the 2:14:1 phase in the samples decreases progressively with increasing C content from 312 °C for x=0 to 270 °C for x=6. © 2002 American Institute of Physics.
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  • 20
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 3797-3805 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Domain structures of unpoled as well as poled (along [001]- and [110]-direction) Pb(Zn1/3Nb2/3)O3 (PZN)-8% PbTiO3 (PT) and Pb(Mg1/3Nb2/3)O3 (PMN)-29% PT single crystals have been investigated by scanning force microscopy (SFM) in the piezoresponse mode, at room temperature. Antiparallel domain structures have been detected mostly in unpoled crystals of both materials, with a fingerprint pattern in (001)-oriented PZN-8% PT crystal. The ferroelastic domain wall has been identified in poled (110)-oriented PZN-8% PT crystal. "Writing" of ferroelectric domains has been performed by applying a dc voltage to the SFM tip. Local re-poling has been observed for all unpoled as well as for poled (001)-oriented crystals at the voltage ±60 V. Local electrical switching was successful in poled (110)-oriented PMN-29% PT at higher voltage (±120 V) but was not successful in poled (110)-oriented PZN-8% PT crystal. Domain-engineered crystals poled in [110]-direction seem to exhibit more stable (in the sense of local re-poling properties) domain arrangement. Hysteretic d(E) dependencies were observed by local application of an ac voltage. © 2002 American Institute of Physics.
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  • 21
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 3785-3796 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In the study of elastic and piezoelectric fields in semiconductors due to buried quantum dots (QDs), the semicoupled piezoelectric model is commonly adopted. However, its accuracy and suitability have never been studied. In this article, by developing a fully coupled piezoelectric model and deriving the analytical elastic and piezoelectric fields based on this and the semicoupled models, we are able to verify that when the piezoelectric coupling is weak, like GaAs with the electromechanical coupling factor g=0.04, the semicoupled model predicts very accurate results as compared to those based on the fully coupled model. However, if the piezoelectric coupling is relatively strong, like AlN with g=0.32, we have shown that the semicoupled model gives very serious errors or even totally wrong results. Applying these two models to a uniformly strained AlN layer grown along the polar axis has also confirmed our observation. Therefore, for semiconductors like AlN, the fully coupled model presented in this article must be employed in order to give a reliable and accurate prediction for the elastic and piezoelectric fields. Also presented in this article is the distribution of the piezoelectric field on the surface of a half-space GaAs due to a buried QD located at 2 nm below the surface with a volume 4π/3 (nm)3. It is observed that the horizontal electric field on the traction-free and insulating surface shows some special features and its maximum magnitude can be as high as 3.5×107 V/m when the uniform mismatch eigenstrain is 0.07. Furthermore, the piezoelectric field on the traction-free and conducting surface exhibits different characters as compared to the traction-free and insulating case. © 2002 American Institute of Physics.
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  • 22
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 3829-3840 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Optically thin palladium metal films evaporated on different silicon based substrates are investigated following exposure to different concentrations of hydrogen gas in air. Laser modulated reflectance off the palladium surface of silicon oxide and silicon nitride substrates is used to recover information regarding the reflectivity inversion and α/β-phases of the palladium complex after both first and multiple gas cycling. Atomic force microscopy confirms the formation of metal nanostructures following exposure to hydrogen of the optically thin palladium films. © 2002 American Institute of Physics.
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  • 23
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 3847-3854 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A detailed systematic study on the growth morphology of carbon nanotubes (CNTs) on Si in atmospheric pressure thermal chemical vapor deposition was undertaken. The role of NH3 for vertical alignment of CNTs was investigated. The direct cause for the alignment was a dense distribution of the catalytic metal particles, but that the particles are maintained catalytically active under amorphous carbon deposits was established by NH3. It allows a dense nucleation of the CNTs, and consequently, assists vertical alignment through entanglement and mechanical leaning among the tubes. The CNTs grew in a base growth mode. Since Ni is consumed both by silicide reaction and by capture into the growing tube, the growth stops when Ni is totally depleted. It occurs earlier for smaller particles, and thus a long time of growth results in a thin bottom with poor adhesion. © 2002 American Institute of Physics.
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  • 24
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 3864-3868 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Pt/Ti/WSi/Ni ohmic contacts to n-SiC, initially annealed at 950 and 1000 °C for 30 s, were evaluated for thermal stability via pulsed/cyclic thermal fatigue and aging experiments at 650 °C. Modifications of material properties in response to cyclic thermal fatigue and aging tests were quantitatively assessed via current–voltage measurements, field emission scanning microscopy, atomic force microscopy, and Rutherford backscattering spectrometry. Negligible changes in the electrical properties, microstructure, and surface morphology/roughness were observed for both annealed ohmic contacts in response to 100 cycles of acute cyclic thermal fatigue. Aging of the 950 °C annealed contact for 75 h at 650 °C resulted in electrical failure and chemical interdiffusion/reaction between the contact and SiC substrate. The 1000 °C annealed contact retained ohmicity after 100 h of aging and was found to be chemically and microstructurally stable. These findings indicate that the 1000 °C annealed Pt/Ti/WSi/Ni ohmic contact to n-SiC is thermally stable and merits strong potential for utilization in high temperature and pulsed power devices. © 2002 American Institute of Physics.
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  • 25
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 4983-4987 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Transmission electron microscopy and x-ray diffraction measurements reveal the presence of stacking faults (SFs) in undoped cubic GaN thin layers. We demonstrate the importance of the defects in the interfacial region of the films by showing that the SFs act as nucleation sites for precipitates of residual impurities such as C and Si present in the GaN layers grown on SiC(001) substrates. We used the imaging secondary ion mass spectroscopy technique to locate these impurities. The systematic decrease of the SF density as a function of the layer thickness is explained by an annihilation mechanism. Finally, the effects of usual dopants on the structural properties of GaN layers are discussed. It is shown that Mg has a tendency to incorporate out of the Ga site by forming Mg precipitates for a concentration higher than 1019 cm−3 in contrast with the results found for heavily Si doped layers. © 2002 American Institute of Physics.
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  • 26
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5016-5023 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Results of thermally stimulated photoluminescence (TSL) measurements in poly(2,5-dioctoxy p-phenylene vinylene) (DOO–PPV) are reported. The obtained results are analyzed in terms of the hopping model of TSL in disordered organic materials. It is shown that the experimentally obtained TSL curve can be fitted on the basis of a double-peak Gaussian density-of-states distribution. The upper peak is associated with intrinsic localized states while the lower one can be ascribed to aggregates. The latter assignment is also supported by measurements of steady-state and time-resolved photoluminescence in DOO–PPV films and solutions. Possible mechanisms of charge carrier photogeneration in DOO–PPV are discussed. © 2002 American Institute of Physics.
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  • 27
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5029-5034 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A theoretical analysis based on a perturbation method is used to elucidate the results of attenuated total reflection (ATR) measurements performed on silicon oxide layers of different thicknesses on silicon substrates. This analysis shows that the absorbance ATR spectrum in p polarization is the image of the layer energy loss function, under specific conditions. It is pointed out that the enhanced sensitivity of ATR is controlled by the air gap thickness, the optical properties of the media involved, and the probing light polarization. An exact ATR spectrum simulation using a matrix formalism showed that straightforward interpretation in terms of the layer dielectric function is limited to a very narrow layer thickness range. The ATR spectrum fitting process is considered for layers out of this range and evaluated for the interpretation of experimental silicon oxide layer spectra. © 2002 American Institute of Physics.
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  • 28
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5041-5044 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of Nb codoping on the optical properties of the PbWO4:Mo scintillator is investigated by radio- and thermoluminescence, scintillation decay, and light yield measurements. Steady-state radioluminescence efficiency of PbWO4:Mo,Nb with optimized doping concentrations (2750 and 350 molar ppm, respectively) becomes up to 20 times higher with respect to that of undoped PbWO4 and is comparable to that of Bi3Ge4O12. However, slow components down to several tens of microseconds appear in the time decay. Their existence may be related to the presence of traps monitored by thermoluminescence. © 2002 American Institute of Physics.
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  • 29
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5051-5054 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The thermal expansion coefficients of a single crystal and ceramic of Nb2O5 are measured in the temperature range of −200–500 °C by the dilatometer technique. Both single crystals and ceramics of Nb2O5 and Nb2O5(1−x):xTiO2 show negative thermal expansion in this temperature range. Some contribution to the result could be due to the presence of the Magneli phases. The main phase transition temperature, which also matches with the dielectric anomaly, occurs at (approximate)150 °C. © 2002 American Institute of Physics.
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  • 30
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5066-5071 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Germanium-doped ZnSe epilayers have been grown on (001)-oriented semi-insulating GaAs substrates by molecular beam epitaxy. The photoluminescence (PL) spectra exhibit strong near-band edge emission similar to those from undoped, chlorine-doped and gallium-doped samples, though some differences exist. The prominent PL peak at 2.795 eV (10 K) is attributed to the germanium-bound exciton recombination and is accompanied by free exciton (2.802 eV), Ia-type exciton (2.785 eV) and Iv-type exciton (2.775 eV) emission peaks. Following an increase in temperature, the intensity of all the IGe, Ia, and Iv emission peaks decreases gradually, indicating the presence of nonradiative recombination mechanisms with thermal activation energies of 40, 70, and 50 meV respectively. However, for the Iv peak, there is one additional nonradiative recombination mechanism in accordance with the thermally activated transfer of excitons from the Iv-type centers to Ia-type centers. This nonradiative recombination mechanism with activation energy of 9 meV is responsible for the decrease of the Iv peak intensity when the sample temperature is changed from 15 to 100 K. Following an increase in temperature, the Iv peak, Ia peak, and germanium-related peak disappear gradually and successively. Finally, the PL spectrum is dominated by free exciton emission at temperatures exceeding 210 K. © 2002 American Institute of Physics.
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  • 31
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5089-5092 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electronic property variations of a two-dimensional electron gas (2DEG) in modulation-doped step quantum wells due to an embedded potential barrier were studied by performing Shubnikov–de Haas (SdH), Van der Pauw–Hall-effect, and cyclotron resonance measurements on two kinds of InxGa1−xAs/InyAl1−yAs step quantum wells which were one without and the other with an embedded barrier. The fast Fourier transformation results for the SdH data at 1.5 K indicated the electron occupation of two subbands in both step quantum wells. The total electron carrier density and the mobility of the 2DEG in the step quantum well with an embedded barrier were smaller than those in the quantum well without an embedded barrier. The electron effective masses were determined from the slopes of the main peak absorption energies as functions of the magnetic field, and satisfied qualitatively the nonparabolicity effects in both quantum wells. The electronic subband energies, the wave functions, and the Fermi energies were calculated by using a self-consistent method taking into account exchange-correlation effects together with strain and nonparabolicity effects. These present results indicate that the electronic parameters in modulation-doped InxGa1−xAs/InyAl1−yAs step quantum wells are significantly affected by an embedded barrier. © 2002 American Institute of Physics.
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  • 32
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5116-5124 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The direct and assisted-by-trap elastic tunnel current in metal–oxide–semiconductor capacitors with ultrathin gate oxide (1.5–3.6 nm) has been studied. Bardeen's method has been adapted to obtain the assisted tunnel current, in addition to the direct tunnel current. The dependence of the assisted current on the trap distribution in energy has also been analyzed. This allows us to obtain the trap distribution in energy from experimental current curves. Finally, we have analyzed the role of the image force, the inclusion of which can avoid a barrier height dependence on the oxide thickness. © 2002 American Institute of Physics.
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  • 33
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5135-5140 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: X-ray photoemission and x-ray photoabsorption were used to study the composition and the electronic structure of ytterbium-doped strontium fluoroapatite (Yb:S-FAP). High resolution photoemission measurements on the valence band electronic structure and Sr 3d, P 2p and 2s, Yb 4d and 4p, F 1s, and O 1s core lines were used to evaluate the surface and near surface chemistry of this fluoroapatite. Element specific density of unoccupied electronic states in Yb:S-FAP were probed by x-ray absorption spectroscopy at the Yb 4d (N4,5 edge), Sr 3d (M4,5 edge), P 2p (L2,3 edge), F 1s, and O 1s (K edges) absorption edges. These results provide measurements of the electronic structure and surface chemistry of this material. © 2002 American Institute of Physics.
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  • 34
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5149-5154 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Extremely thin titanium nitride (TiN) barrier layers for Cu based interconnects were deposited using metal organic chemical vapor deposition. The effect of the subsequently performed nitrogen/hydrogen plasma treatment on the microstructure, composition, and electrical properties of these films is studied using conventional and high resolution transmission electron microscopy, Auger electron spectroscopy, and four point probe resistivity measurements. In the studied system the crystallization of the TiN film starts from an amorphous matrix and a polycrystalline morphology is developed upon the H2/N2 plasma treatment. After a short plasma treatment, most of the film is already crystalline and consists of grains of a few nanometers in diameter. Continued plasma treatment leads to grain growth and a significant reduction of contaminants such as oxygen and carbon. The resistivity of the films drops with plasma treatment time, and a correlation between resistivity and oxygen content is found, which suggests that oxygen in the grain boundaries plays a decisive role for the resistivity of the films. It is shown that the oxygen in the grain boundaries leads to an electron reflectance of 0.9. Thus, the oxygen accumulation in the grain boundaries is the limiting factor for the reduction of film resistivity by plasma treatment. © 2002 American Institute of Physics.
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  • 35
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5155-5157 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of periods on the accumulation and release of stress in GaAs/AlInAs superlattices structure is reported here. It is observed that in GaAs/AlInAs superlattices, when the Indium (In) content is greater than 10%, stress accumulates monotonically as the number of period increases. In GaAs/AlInAs superlattices with an In content of 5%, the accumulated stress is larger when the number of periods is less than 10. However when the number of periods exceeds 10, it was observed that suddenly there is a significant increase in defects and stress release. However, with any further increase in period number, there is once again an accumulation of stress. © 2002 American Institute of Physics.
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  • 36
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5158-5162 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Five electron traps were detected successfully in heavily Si-doped GaAs and AlxGa1−xAs of low Al content with a Si concentration of above 1×1019 cm−3 using deep level transient spectroscopy. The junctions were grown by liquid phase epitaxy and were strongly compensated. The traps were investigated for functions of the Si concentration and the AlAs mole fraction. The traps are discussed in terms using their spectra and concentration as opposed to the previous results which used point defects in the GaAs and AlGaAs. The traps show distinctive features, which can be attributed to strongly Si-compensated crystals. Three traps among them were confirmed to be DX centers. © 2002 American Institute of Physics.
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  • 37
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5170-5175 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using a theoretical model of a bilayer organic light emitting diode, we calculate numerically the evolution of carrier densities and electric fields inside the device. The obtained results allow us to detail injection and accumulation of carriers during transient excitation. Charge densities as a function of applied voltage present two distinct thresholds which determine three operating ranges: no injection, unipolar injection, and bipolar injection. Dynamically these thresholds depend on the rise time of the applied voltage and have a clear signature in the current densities. We show that the electroluminescence threshold has static and dynamic values which may be different. Calculated external current in response to a voltage ramp presents two steps related to the evolution of the capacity of the device. This capacitive behavior is observed experimentally. © 2002 American Institute of Physics.
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  • 38
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5176-5181 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This paper analyzes a simplified rate equation model of localized exciton emission in GaInN. Expressions for temperature dependent photoluminescence (PL) efficiency and decay time are derived and compared with time integrated (TIPL) and time resolved photoluminescence (TRPL) data for a series of multiquantum well light emitting diodes with varying In composition in the active region. Time resolved photoluminescence is measured up to relatively high temperature (540 K) and a decreasing efficiency coupled with a peak energy decay time that is weakly dependent on temperature is observed. The decay time at peak emission energy begins to decrease at a temperature that depends on the In content in the quantum wells. The analysis developed here demonstrates that application of the expressions τr=τpl/η and τnr=τpl/(1−η) is not sufficient to determine radiative and nonradiative lifetimes from TRPL and TIPL data in the GaInN system. (Here τr is the radiative decay time, τnr is the nonradiative decay time, τpl is the measured PL decay time, and η is the measured TIPL intensity normalized to the low temperature intensity.) GaInN with even small amounts of In exhibits highly efficient luminescence due to recombination through localizing centers. As relaxation occurs into both defects and localizing states after initial generation with the above GaInN band gap excitation, the number of carriers arriving at localization centers can change with temperature. This temperature dependent change should be considered when calculating relevant decay times from TRPL and TIPL data. This mechanism is distinct from an increase in the intrinsic radiative decay time obtained by applying conventional analysis to extract radiative and nonradiative lifetimes from TRPL and TIPL data. © 2002 American Institute of Physics.
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  • 39
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5200-5202 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Avalanche breakdown voltages were determined for a series of In0.53Ga0.47As p-i-n diodes with i-region thicknesses ranging from 0.4 to 4.79 μm using measurements of reverse dark current and phase-sensitive photomultiplication. Despite its narrower bandgap In0.53Ga0.47As is found to have a very similar breakdown voltage to GaAs. © 2002 American Institute of Physics.
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  • 40
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5203-5207 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Multi-quantum-well GaN/InGaN heterojunction diodes prepared by metalorganic chemical vapor deposition on sapphire showed effects of strong tunneling in their I–V characteristics. The space charge region was shown to be located in the GaN/InGaN superlattice (SL). The injection of moderately high forward currents through the structure for several hours enhanced the overall tunneling through the structure and facilitated faster tunneling between the layers in the GaN/InGaN SL. These results may have relevance to the aging characteristics of light-emitting diodes under bias. © 2002 American Institute of Physics.
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  • 41
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5221-5226 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Current and voltage noise measurements have been carried out on nanoparticle WO3 films. The fluctuation dissipation theorem holds, which indicates that the observed noise is an equilibrium phenomenon. Results on the thinnest films show that noise measurements can be used for quality assessment of nanocrystalline insulating films. © 2002 American Institute of Physics.
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  • 42
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5227-5229 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Fe–Co–Nd–Dy–B glassy alloys are a current type of ferromagnetic material. To increase their glass-forming ability against the growth of a crystallization phase, the effects of the addition of transition metals TM (TM=V, Nb, Ta, Cr, Mo, and W) on the glass-formation ability and magnetic properties of Fe62Co9.5Nd3Dy0.5B25 glassy alloy have been investigated. The substitution of 2 at. % elements TM (=Nb, Ta, Mo, and W) for Fe and Co increases crystallization temperature Tx and decreases the onset temperature of solidification Tm, leading to a significant increase in the thermal stability against crystallization for Fe60.3Co9.2TM2Nd3Dy0.5B25. The difference (ΔTx=Tx−Tg) between Tx and the glass transition temperature Tg increases from 55 K at 0 at. % TM to 87 K at 2 at. % TM. The bulk glassy alloy with a diameter up to 1.2 mm was produced by copper mold casting. Also no distinct changes in Tg, Tx and ΔTx are seen for the addition of Cr and V. The results can be explained by the difference of atomic size in the additional elements. The saturation magnetization decreases slightly by the addition of 2 at. % TM elements. The saturation magnetization and coercive force of glassy Fe60.3Co9.2TM2Nd3Dy0.5B25 alloys are 1.13 to 1.19 T and 3.85–4.98 A/m, respectively. © 2002 American Institute of Physics.
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  • 43
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5234-5239 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ti/Co/NiFe/Al-oxide/NiFe (F1) and Co/NiFe/Al-oxide/NiFe (F2) junction films were characterized using high-resolution electron microscopy (HREM), Lorentz transmission electron microscopy (LTEM), and alternating gradient force magnetometry (AGFM). HREM images showed that the Ti seed layer induced a strong 〈111〉 texture in the bottom Co/NiFe bilayer. The ferromagnet/Al-oxide interfaces in F1 showed correlated waviness, while the interface waviness in F2 appeared uncorrelated. Thus, "orange-peel" coupling effect was more significant in F1 than in F2, which was confirmed by the steep slope of the magnetization curve in the "antiparallel" magnetization configuration for F1. The LTEM in situ magnetizing experiment results and the AGFM measurement of magnetization curves showed that both junction films possessed a two-stage magnetization reversal characteristic—magnetization of the top NiFe layer reversed first followed by the reversal of the bottom Co/NiFe bilayer. LTEM observation revealed that the magnetization reversal of the top NiFe layer was via domain wall motion, while the reversal of the bottom Co/NiFe bilayers was mainly by wall motion together with a small degree of moment rotation. Domain wall mobility in the Co/NiFe bilayer of F1 was higher due to the strong crystallographic texture and large grain size appeared in the bilayer. © 2002 American Institute of Physics.
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  • 44
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    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present here a magnetic tunnel junction device using perpendicular magnetization films designed for magnetic random access memory (MRAM). In order to achieve high-density MRAM, magnetic tunnel junction devices with a small area of low aspect ratio (length/width) is required. However, all MRAMs reported so far consist of in-plane magnetization films, which require an aspect ratio of 2 or more in order to reduce magnetization curling at the edge. Meanwhile, a perpendicular magnetic tunnel junction (pMTJ) can achieve an aspect ratio=1 because the low saturation magnetization does not cause magnetization curling. Magnetic-force microscope shows that stable and uniform magnetization states were observed in 0.3 μm×0.3 μm perpendicular magnetization film fabricated by focused-ion beam. In contrast, in-plane magnetization films clearly show the presence of magnetization vortices at 0.5 μm×0.5 μm, which show the impossibility of information storage. The PMTJ shows a magnetoresistive (MR) ratio larger than 50% with a squareness ratio of 1 and no degradation of MR ratio at 103 Ω μm2 ordered junction resistance. © 2002 American Institute of Physics.
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  • 45
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5260-5267 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: For an infinitely long bar with rectangular cross section 2a×2b and constant susceptibility χ in a uniform transverse applied field Ha along dimension a, the fluxmetric and magnetometric demagnetizing factors Nf,m as functions of a/b and χ are accurately computed using a finite-elements method. By comparison of the computed results with exact analytical results for χ=−1,0,∞ and with a set of conjugate relations derived in this work, the elements distributions have been optimized to give a minimum discretization error. This error is further greatly reduced in the final results of Nf,m by using an error correction approach previously proposed in a similar work for cylinders. © 2002 American Institute of Physics.
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  • 46
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5423-5428 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of thermal stress on the electrical characteristics of metal–oxide–semiconductor diodes with oxides in an ultrathin regime were studied. By centering a quartz ring as a heat sink beneath the silicon wafer, the introduced temperature gradient results in a corresponding hat-like shape thickness distribution for an oxide grown on the wafer with a rapid thermal processing system. The enhanced exterior tensile and compressive thermal stresses due to introduced temperature gradient make the oxides exhibit less and more substrate injection saturation current Jsat, respectively, in comparison to control oxides. Their flatband voltage VFB data also clearly show the dependency of effective charge number density Neff on exterior thermal stress. A stress distribution model is proposed to explain the observation. Co-60 irradiation was also performed on the stressed samples to observe this stress extent by examining the variation of electrical characteristics. It was found that an oxide grown on a wafer in exterior compression exhibited better radiation hardness than one in tension. © 2002 American Institute of Physics.
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  • 47
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5434-5437 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The layer-by-layer hydrogen plasma treatment method, alternatively repeating the process of nanometer thickness film deposition and hydrogen plasma chemical annealing, was applied to fabricate amorphous carbon (a-C) films. It was shown that hydrogen plasma treatment reduced the size of sp2 clusters and resulted in the increase of the optical band gap. Consequently, a stable vacuum electron emission with a low threshold field was achieved from layer-by-layer hydrogen plasma annealed a-C films compared with that from conventionally deposited samples. The threshold electric field was as low as 2 V/μm. The improvement of field emission characteristics could be attributed to the large field enhancement effect due to the inhomogeneous distribution of nanometer scale sp2 clusters. © 2002 American Institute of Physics.
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  • 48
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5438-5441 
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    Source: AIP Digital Archive
    Topics: Physics
    Notes: A Fokker–Planck equation for carrier transport in semiconductors is derived from the Boltzmann transport equation by expanding in Legendre polynomials and assuming the phonon energy exchanged at momentum randomizing collisions is small compared with the mean carrier energy. The method is used to compute impact ionization probability distributions in space and time and the results agree well with those generated by an equivalent Monte Carlo model over a wide range of electric fields from 300 kV/cm to 1 MV/cm. © 2002 American Institute of Physics.
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  • 49
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 1921-1927 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The dynamic high-strain-rate behavior of two-phase TiB2+Al2O3 ceramics with biased microstructures was investigated in this study. The microstructural bias includes differences in phase (grain) size and phase distribution such that in one case a continuous (interconnected) TiB2 network surrounds the Al2O3 phase (qualitatively termed "T@A") and in another case the TiB2 and Al2O3 phases are interdispersed and uniformly intertwined with each other (qualitatively termed "TinA"). Quantitative microscopy was used to characterize the phase size and the integral curvature which is taken as a measure of TiB2 phase connectivity around Al2O3. Dynamic compression and tension (spall) properties were measured using plate impact experiments. The measurements used piezoelectric polyvinyldine fluoride stress gauges to obtain the loading profile and to determine the Hugoniot elastic limit. In addition, velocity interferometry system for any reflector interferometry was used to obtain the spall signal and the tensile dynamic strengths of the materials. Experimental results reveal that while the σHEL and the compressive strengths of TiB2+Al2O3 ceramics are dependent on the average grain (phase) size, the tensile (spall) strength scales with the TiB2-phase connectivity. This result suggests that the interconnected TiB2/Al2O3 microstructural morphology provides a stronger impediment to failure in tension compared with the morphology with simply interdispersed phases. © 2002 American Institute of Physics.
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  • 50
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 1963-1972 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Two spatial dimension front tracking simulations have been performed to study the growth of polycrystalline, faceted films from randomly oriented nuclei by varying the deposition angle of the incident flux during physical vapor deposition. The orientation of grain columns, the porosity, the crystallographic texture, and grain size are sensitive to the deposition angle. The origin of this effect is widely believed to be associated with shadowing. In order to isolate the effects of shadowing from other physical effects (such as surface diffusion, deposition species size, flux divergence, etc.), we have constructed a simulation where all of these effects are completely removed. These simulations demonstrate that while many of the observed structural properties of obliquely deposited films are controlled by shadowing, a few key properties cannot be attributed solely to shadowing. © 2002 American Institute of Physics.
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  • 51
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5507-5507 
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    Topics: Physics
    Notes: © 2002 American Institute of Physics.
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  • 52
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5507-5507 
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    Topics: Physics
    Notes: © 2002 American Institute of Physics.
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  • 53
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5508-5508 
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    Topics: Physics
    Notes: © 2002 American Institute of Physics.
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    Journal of Applied Physics 91 (2002), S. 5508-5508 
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    Source: AIP Digital Archive
    Topics: Physics
    Notes: © 2002 American Institute of Physics.
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 3955-3980 
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    Source: AIP Digital Archive
    Topics: Physics
    Notes: Optical waveguide amplifiers based on polymer materials offer a low-cost alternative for inorganic waveguide amplifiers. Due to the fact that their refractive index is similar to that of standard optical fibers, they can be easily coupled to existing fibers with low coupling losses. Doping the polymer with rare-earth ions that yield optical gain is not straightforward, as the rare-earth salts are poorly soluble in the polymer matrix. This review article focuses on two different approaches to dope a polymer waveguide with rare-earth ions. The first approach is based on organic cage-like complexes that encapsulate the rare-earth ion and are designed to provide coordination sites to bind the rare-earth ion and to shield it from the surrounding matrix. These complexes also offer the possibility of attaching a highly absorbing antenna group, which increases the pump efficiency significantly. The second approach to fabricate rare-earth doped polymer waveguides is obtained by combining the excellent properties of SiO2 as a host for rare-earth ions with the easy processing of polymers. This is done by doping polymers with Er-doped silica colloidal spheres. © 2002 American Institute of Physics.
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 3988-3991 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a method for calculating band structures for one-dimensional Kerr nonlinear photonic crystals, which exhibit an optical switching function. The band structure shows the allowed modes for the nonlinear photonic crystal as a function of the magnitude of the nonlinearity. The dielectric band is found to be most suited for the control beam as it is least effected by the nonlinearity. The third band is more sensitive to the nonlinearity and thus suited for the probe beam. Also the wavelength dependence of the switching function can be estimated using our method. The applied Fourier method is found to be robust in describing the effect of the nonlinearity. © 2002 American Institute of Physics.
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 3992-3999 
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    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present results of the experimental determination of the optical nonlinearities induced by heating free electrons distributed in the multivalley conduction band of highly doped n-GaAs. We propose a very sensitive multilayer leaky waveguide structure for transverse magnetic polarized waves in order to drastically reduce the required optical intensities. We explain in depth the dependence of the optical nonlinearity on doping concentration and deformation potentials. For a doping concentration no of 7.6×1018 cm−3, we found a nonlinear refractive index value n2(approximate)(1(minus-plus)0.2)×10−6 cm2/W at λ=10.6 μm, by fitting nonlinear reflection measurements with an equivalent intervalley deformation potential value ΛLL=(1.0±0.30)×109 eV/cm. © 2002 American Institute of Physics.
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  • 58
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 3981-3987 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In order to increase the crystallization speed and data transfer rate (DTR), a superlattice-like structure (SLL) was applied to the recording layer of phase change optical disks. Unlike the conventional phase change layer, the recording layer with the SLL structure consisted of alternating thin layers of two different phase change materials, i.e., GeTe and Sb2Te3. Although neither GeTe nor Sb2Te3 could be used as a phase change layer material for practical applications, present experimental results revealed that the phase change optical disk with the SLL structure demonstrated an excellent recording property that could meet practical recording requirements. X-ray photoelectron spectroscopy was employed to confirm that the SLL structure could be preserved after many times of melting and quenching. Dynamic properties of the optical recording disk with the SLL structure were investigated with a 1 T pulse duration of 8 ns and a constant linear velocity of 19 m/s. A clear eye pattern was observed. The carrier-to-noise ratio was about 58 dB and a DTR of 47 Mbit/s was achieved. The DTR would be as high as 140 Mbit/s if the blue light is used. It has been proven that the SLL structure is a useful means to increase the DTR of phase change optical recording disks. © 2002 American Institute of Physics.
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  • 59
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1727-1743 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The model of space-charge formation in photorefractive polymers due to Schildkraut and Buettner has been modified to include thermally accessible deep traps as well as shallow traps. The dynamic equations have been solved semiempirically using independent measurements of photoconductive properties to predict photorefractive dynamics. Dependencies of the dynamics on charge generation, mobility, trap density, acceptor density, ionized acceptor density, as well as their associated rates are examined. The magnitude of the fast time constant of photorefractive development is successfully predicted. The introduction of deep traps into the model has allowed us to qualitatively predict the reduction in speed due to deep trap filling and ionized acceptor growth. Experimental studies of photoconductivity and photorefraction (PR) in several polyvinyl carbazole photorefractive composites are carried out to demonstrate the applicability of the model. By choosing chromophores with different ionization potentials and by varying the chromophore concentrations, we investigate the influence of the chromophore ionization potential on the photoelectric and PR properties and reveal the nature of deep traps in the composites and their contribution to both photoconductivity and PR dynamics. Effects of plasticizer components are also discussed. © 2002 American Institute of Physics.
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1744-1751 
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    Source: AIP Digital Archive
    Topics: Physics
    Notes: Fully leaky guided optical modes are used to explore the director profile in a twisted nematic liquid crystal cell built using a pair of high-index glass plates. This allows access to the pseudocritical angles corresponding to the liquid-crystal indices. Optical data is recorded over a range of angles of incidence with the cell subject to ac voltages. At higher-applied fields, the director in the cell center aligns almost homeotropically. Then the two surface regions become elastically decoupled, the directors at the surfaces realigning along the original alignment axes. Beyond the pseudo-critical angle corresponding to the low index of the liquid-crystal two minima of the polarization conserving transmission signal, for transverse electric polarization, TSS (over a particular range of incidence angles) are found as the cell rotation angle is changed. These two minima give the original alignment directions of the director, the easy axes, at the two substrates, information vital to the measurement of the torsional anchoring energies at the interfaces of the cells. © 2002 American Institute of Physics.
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1752-1756 
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    Source: AIP Digital Archive
    Topics: Physics
    Notes: We discuss the formation of pretilt by oblique irradiation of photosensitive polymers that homogeneously align liquid crystals in the direction corresponding to the maximum density of unreacted polymer. We show that a tilted polymer distribution is formed by oblique illumination with one beam of unpolarized or partially polarized light. When unpolarized radiation is used, a small azimuthal anisotropy is generated and the polymer tilt angle increases with incident angle. Pretilted liquid crystal alignment is possible up to a threshold angle at which the azimuthal alignment direction changes. Irradiation with partially polarized light gives a higher azimuthal anisotropy but smaller polymer tilt angles. We obtain liquid crystal pretilt angles up to 4° by oblique irradiation of polyimide with light from an excimer laser operating below the threshold for ablation. A simple two step process is used to obtain pretilted alignment for liquid crystals using surface gratings: a grating etched into polyimide by laser ablation is subsequently irradiated at oblique incidence to give planar liquid crystal alignment with a pretilt angle of 3°. © 2002 American Institute of Physics.
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  • 62
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    Topics: Physics
    Notes: Laser Thomson-scattering diagnostics of electron energy distribution function (EEDF) was carried out for inductively coupled cyclo–C4F8/Ar and CF4/Ar plasmas at 25 mTorr. Care was taken to ascertain that the observed Thomson spectra are unaffected by other laser-induced effects, in particular by Raman scattering. Admixing of C4F8 and CF4 with Ar resulted in marked deviation of EEDF from Maxwellian. The mechanism leading to non-Maxwellian EEDF was also studied by a Monte Carlo simulation. The results suggest that the major factors responsible are rapid electron energy loss due to vibrational excitation and the effect nonlocal electron kinetics associated with localized electron heating. © 2002 American Institute of Physics.
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    Journal of Applied Physics 91 (2002), S. 4090-4094 
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    Source: AIP Digital Archive
    Topics: Physics
    Notes: We analyze the 1.5μm wavelength operation of a room temperature polarization switch based on electron spin dynamics in InGaAsP multiple quantum wells. An unexpected difference in response for left and right circularly polarized pump light in pump–probe measurements was discovered and determined to be caused by an excess carrier induced birefringence. Transient polarization rotation and ellipticity were measured as a function of time delay. © 2002 American Institute of Physics.
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  • 64
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 4101-4104 
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    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoreflectance (PR) of surface-intrinsic-n+ type doped GaAs has been measured for various power densities of pump laser. The spectra exhibited many Franz–Keldysh oscillations, whereby the strength of electric field F in the undoped layer can be determined. The thus obtained Fs are subject to photovoltaic effect and are less than built-in field Fbi. In the previous work we have obtained the relation F(approximate)Fbi−δF/2 when δF(very-much-less-than)Fbi by using electroreflectance to simulate PR, where δF is the modulating field of the pump beam. In this work a method was devised to evaluate δF by using photoinduced voltages Vs and, hence, the relation can be verified by PR itself. The δFs obtained by Vs are also consistent with those of using imaginary part of fast Fourier transform of PR spectra. © 2002 American Institute of Physics.
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    Journal of Applied Physics 92 (2002), S. 1793-1798 
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    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoreflectance (PR) spectra have been measured to determine the lowest direct-band edge E0α (α=A, B, and C) of wurtzite CdS single crystal in the temperature range T=13–300 K for both E⊥c and E(parallel)c polarizations. The measured PR spectra can be interpreted by the three-dimensional (3D) excitonic plus one-electron line shapes over the entire temperature range. The temperature dependence of the excitonic and critical-point parameters (energy, amplitude, and broadening parameter) have been determined and analyzed using the Varshni [Physica (Amsterdam) 34, 149 (1967)] equation and an analytical four-parameter expression recently developed for the explanation of the band-gap shrinkage effect in semiconductors. The 3D- exciton binding energies have also been determined to be 27 (A), 31 (B), and 30 meV (C), respectively. © 2002 American Institute of Physics.
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  • 66
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1788-1792 
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    Source: AIP Digital Archive
    Topics: Physics
    Notes: Analysis of discharge mechanism in especially designed pseudosparks that facilitate pseudospark characteristic low-erosive conduction at very high currents is presented. The alternate formulation of criterion for transition to arc discharge phase developed here enables us to account for the emergence of arcs at each aperture after a threshold electric charge is transmitted in these devices. The use of a large number of apertures is found to have no influence on discharge condition that initiates arc formation at individual apertures. © 2002 American Institute of Physics.
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    Journal of Applied Physics 92 (2002), S. 1799-1802 
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    Source: AIP Digital Archive
    Topics: Physics
    Notes: Formation of the anomalous cellular structure in (100) GaSb with Sn ion-implantation at a low temperature is investigated by cross-sectional scanning electron microscopy, atomic force microscopy, and transmission electron microscopy. A fine structure consisting of many cells was formed on GaSb surface implanted by 60 keV Sn. The cell diameter and the thickness of the walls partitioning the cells were about 50 and 10 nm, respectively, which are almost constant in the range of the ion dose 4.0×1014–8.9×1014 ions/cm2. The depth of the cells increased linearly with increasing ion dose, from 100 nm in the sample implanted with a dose of 4.0×1014 ions/cm2 to 220 nm in that implanted with a dose of 8.9×1014 ions/cm2. From the experimental results, it is concluded that the development of the cellular structure originates in formation of the voids. An improved defect formation mechanism based on movement of the implantation-induced point defects is discussed. © 2002 American Institute of Physics.
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  • 68
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    Journal of Applied Physics 91 (2002), S. 4143-4148 
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    Source: AIP Digital Archive
    Topics: Physics
    Notes: Pressure-volume (P–V) data were measured for Ta up to 69 GPa at T=298 K using angle-dispersive synchrotron x-ray diffraction in combination with diamond anvil cell techniques. Nitrogen and sodium were used as quasihydrostatic pressure media. The obtained P–V relation is compared to experimental and recent theoretical results. Some advantages and limitations of using Ta as a pressure marker in high-resolution x-ray diffraction experiments with diamond anvil cells are discussed. © 2002 American Institute of Physics.
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    Journal of Applied Physics 91 (2002), S. 4149-4153 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The optical gaps of B2O3 alkali borate, and alkali fluoroborate glasses were determined by using blown films. The gap of B2O3 glass was 8.0 eV and the value decreased monotonically with decreasing the B2O3 content in both fluoroborate and borate glasses. When compared at a constant B2O3 content, the gap is in the order Li〉Na〉K and fluoroborate〉borate. Ab initio molecular orbital calculation on the model clusters of the glasses revealed that the lowest excitations in B2O3 and alkali (fluoro) borate glasses are the transitions from nonbonding 2p orbitals of oxygen atoms in boroxol rings to vacant nonbonding 2p orbitals of boron atoms on "loose" BO3 triangles and from nonbonding 2p orbitals of oxygen atoms bonded with borons in tetrahedral coordination to the vacant ns orbitals of neighboring alkali ions, respectively. The vacant ns orbitals of the alkali ions neighboring oxygen atoms attached to tetrahedral borons primarily contribute to the lowest unoccupied molecular orbital (LUMO) levels. On the other hand, fluorine indirectly contributes to lowering the highest occupied molecular orbital (HOMO) levels via inductive effect (polarization of B(Single Bond)F σ-bond). It was therefore concluded that the effect of alkali addition on lowering LUMO levels is larger than that of fluorine addition on lowering the HOMO level. © 2002 American Institute of Physics.
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    Journal of Applied Physics 91 (2002), S. 4163-4170 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of the electron diffraction in highly oriented pyrolytic graphite are studied in an incident electron beam of energy range 500–700 eV using scanning Auger microscopy. The intensity of the exiting electrons monitored by a cylindrical-mirror analyzer can be well interpreted as the joint effect of incident and exit forward focusing along the close-packed 〈21¯1¯2〉-type atomic chains, with the contribution from forward focusing along the secondary close-packed atomic chains increasing rapidly as the beam energy increases. Incident beam effects contribute greatly to the variation in the intensity of the exiting electrons. Increasing the beam energy in this range also increases the anisotropy observed in the angular distribution of the intensity of both elastically scattered and Auger electrons. © 2002 American Institute of Physics.
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    Journal of Applied Physics 91 (2002), S. 4177-4180 
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    Source: AIP Digital Archive
    Topics: Physics
    Notes: We observe ultraviolet-light-induced absorption changes in spectral regions from the near-ultraviolet to the near-infrared in as-grown LiNbO3:Mg. Such a broad light-induced absorption band is unstable at room temperature and decays nonmonoexponentially in the dark with a time constant on the order of tens of seconds. We attribute the appearance of the broadband light-induced absorption to the creation of the intermediate state O− in which holes excited from deep defect centers are trapped at O2− sites near cation vacancies. It is also found that near-infrared photorefractive sensitivities increase by several orders of magnitude by pre-exposing the crystal to incoherent ultraviolet light. These properties may be useful for an application of LiNbO3:Mg to nonvolatile two-color holography. © 2002 American Institute of Physics.
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  • 72
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    Notes: Real-time infrared attenuated total reflection (ATR) spectroscopy and spectroscopic ellipsometry (SE) have been applied to assess depth profiles of Si–Hn (n=1–2) bonding modes in Si:H thin films. We have established an ATR data analysis procedure and the depth profiles of the Si–Hn bonding modes were readily obtained from incorporation rates of Si–Hn bonds at each film thickness estimated by SE. In an attempt to investigate the nucleation reaction of microcrystalline silicon (μc-Si:H) from the hydrogenated amorphous silicon (a-Si:H) phase, a series of Si:H thin films were prepared by an rf plasma-enhanced chemical vapor deposition using various hydrogen dilution ratios R=[H2]/[SiH4]. Real-time ATR and SE revealed that hydrogen content in the a-Si:H layers is uniform toward the growth direction. On the contrary, in the μc-Si:H film deposited at high R, a drastic reduction in the SiH hydrogen content is observed after the μc-Si:H nucleation, whereas the SiH2 hydrogen content is not sensitive to the phase transition. We find a weak variation in the hydrogen content in the a-Si:H layers deposited at various R, and no significant changes are observed in the a-Si:H bulk layers formed at onsets of μc-Si:H nucleation. The above results suggest that the μc-Si:H nucleation reaction occurs near the a-Si:H surface, but not in the a-Si:H bulk layer. © 2002 American Institute of Physics.
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    Journal of Applied Physics 91 (2002), S. 4205-4212 
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    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of sodium on the performance of CuInSe2-based solar cells has been under discussion for already a decade. We present experimental evidence using secondary ion mass spectroscopy, x-ray photoelectron spectroscopy (XPS) and other, complementary physical characterization methods, which indicate that, after exposure to an external Na source, no significant amounts of sodium, beyond the residual amount, found in as-grown samples, enter intact crystals, except via defects such as grain boundaries. However, after such exposure, sodium is found in significant concentrations on crystal surfaces, something that is accompanied by an increase in oxygen concentration, as judged by XPS. As expected metallic Na attacks the crystals and can destroy them or at least introduce significant defect densities. Adding Se0 is found, via Na2Se formation, to temper Na activity specifically its effects on crystal disintegration. This is different from the effect of Se0 along where annealing (of n-type) crystals results in n to p type conversion by Cu outdiffusion. © 2002 American Institute of Physics.
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    Journal of Applied Physics 91 (2002), S. 4229-4232 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have obtained optical second harmonic (SH) intensity images of a silver grating surface. A stripe pattern was seen in the SH intensity image when the incident light polarization is perpendicular to the lines of the grooves of the grating. We have found that the strongest SH radiation comes from the bottoms of the grooves. On the other hand, the strong linear reflection comes from the slope of the grooves. We suggest that the enhancement of the electric field at the bottoms of the grooves has led to the observed strong SH radiation. © 2002 American Institute of Physics.
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    Journal of Applied Physics 91 (2002), S. 4233-4237 
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    Source: AIP Digital Archive
    Topics: Physics
    Notes: We investigated the structural evolution of GaN nucleation layers in the initial growth stages on commercial c-plane sapphires with atomic steps at the surface, using field-emission scanning electron microscopy, synchrotron x-ray scattering, and high-resolution electron microscopy. GaN nucleates into islands preferentially on the atomic steps. The initial small islands of 25 Å high have well-ordered cubic sequences and nearly coherent interfacial structures with a large compressive strain of ∼10%. As the islands grow to 50 Å high, the strain is drastically reduced, to less than 1%, by generating misfit dislocations at the interface and forming the six-to-seven matched interfacial structure. Interestingly, stacking faults are developed from the GaN/sapphire interface, which induces a cubic–hexagonal transformation. The changes in the stacking order during the initial growth are investigated quantitatively. © 2002 American Institute of Physics.
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    Journal of Applied Physics 91 (2002), S. 4242-4248 
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    Source: AIP Digital Archive
    Topics: Physics
    Notes: High-energy (MeV) implantation of Al+ or B+ into 4H-SiC epilayers has been investigated. A 3 μm deep pn junction was formed by multiple-step Al+ or B+ implantation with implantation energies up to 6.2 or 3.4 MeV, respectively. Rutherford backscattering channeling and cross-sectional transmission electron microscopy analyses have revealed residual damages in the implanted layers even after high-temperature annealing at 1600–1800 °C. Nevertheless, high electrical activation ratios over 90% have been achieved for both Al+- and B+-implanted layers by annealing at 1800 °C. Mesa pin diodes with a 15-μm-thick i layer formed by MeV implantation have exhibited high breakdown voltages of 2860–3080 V. The reverse characteristics of diodes have been substantially improved by increasing annealing temperature up to 1800 °C. The diode performance is discussed with the results of deep level analyses near the junctions. © 2002 American Institute of Physics.
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  • 77
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    Notes: We have investigated the effects of the stoichiometry of SiOx and SiNx capping layers on the band gap energy shift induced by impurity-free vacancy disordering of the In0.2Ga0.8As/GaAs multiple quantum well structures. The stoichiometry of the SiOx and SiNx capping layers was changed by varying the flow rate of silane (SiH4) gas, and argon gas was employed as the carrier gas of the diluted SiH4 gas to eliminate any possible incorporation of nitrogen into the deposited film when nitrogen gas is employed as the carrier gas. A blueshift of photoluminescence peak of up to 112 meV is observed after rapid thermal annealing at 950 °C for 50 s from the sample capped with SiOx (provided with a SiH4 flow rate of 20 sccm). It is observed that the magnitude of the blueshift increases with the decrease of SiH4 flow rate for the SiOx and SiNx capping layer because of the increased porosity of dielectric capping layers. The insertion of intermediate GaAs cap layer reduces the band gap energy shift irrespective of the SiOx or SiNx capping layer. © 2002 American Institute of Physics.
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1248-1255 
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    Source: AIP Digital Archive
    Topics: Physics
    Notes: The mean energy necessary to generate an electron-hole pair in gallium arsenide by x and γ photons has been measured in the 230–320 K temperature range. The experimental apparatus consists of a Schottky junction on a high-quality epitaxial GaAs, a silicon detector that generates a reference charge signal and highly stable low-noise electronics. The resolution of the system in measuring the generation energy is better than 2 meV. An apparent value of cursive-epsilon=4.216 eV has been measured at 300 K, lower than previously published values of 4.35 and 4.27 eV for α particles and 4.57 eV for electrons. Charge trapping in the GaAs detector, although very weak (less than 1%), has been observed and a model, based on the Hecht theory, has been developed to derive the true value of cursive-epsilon=4.184±0.025 eV at 300 K. The dependence of cursive-epsilon on the temperature, in the 230–320 K range, has been found linear, cursive-epsilon=4.55−0.00122×T [eV]. The dependence of cursive-epsilon on the band gap has been determined cursive-epsilon=2.76×Eg+0.257 [eV], in good agreement with the Shockley-Klein theory. At 300 K, the found value of cursive-epsilon in GaAs, together with those reported for germanium and silicon, yields a linear dependence of cursive-epsilon on the band-gap energy cursive-epsilon=1.83×Eg+1.6 [eV], with a correlation coefficient of 0.9997. © 2002 American Institute of Physics.
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    Journal of Applied Physics 92 (2002), S. 1262-1267 
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    Topics: Physics
    Notes: Semiconductor lasers with third order waveguide mode emission are a promising way in which to achieve microsources of twin photons. The transport of electrons and holes in these particular structures is a critical issue. The temperature and pumping energy dependence of the photoluminescence spectra of a semiconductor structure specially designed for third order mode emission at 775 nm is studied. The analyses show that transfer of carriers from satellite double heterojunctions to the quantum well through a 140 nm Al0.50Ga0.50As barrier is very efficient, and the population inversion required for lasing is always obtained first in the quantum well rather than in the double heterojunctions at both low and room temperature. © 2002 American Institute of Physics.
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    Journal of Applied Physics 92 (2002), S. 1268-1273 
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    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electrochromic properties of Ni oxide films grown at different working pressures (2.7, 5, 15, and 20 mTorr) by rf sputtering were investigated by means of in situ transmittance measurement and the resulting data were related to the crystallographic structure, surface morphology, and film density. At working pressures of over 5 mTorr, the sputter-deposited Ni oxide films crystallized gradually due to the plasma heating effect at a low growth rate. Although the Ni oxide film grown at 2.7 mTorr had the same amorphous crystallographic structure as the film grown at 5 mTorr, the former had a considerably more inhomogeneous surface and a much lower film density due to the rapid growth rate, and resulted in a defect-rich Ni oxide film. The electrochromic properties, such as the transient cycling period, coloration efficiency, and coloring/bleaching response times, were best for the sample grown at 5 mTorr and they are discussed in terms of defect-rich and crystalline Ni oxide films. © 2002 American Institute of Physics.
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  • 81
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1280-1285 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A quantitative analysis of the influence of temperature and modulation frequency on the thermal activation coupling term in laser photothermal theory is performed. Until now it was taken for granted that the coupling term is negligible only in the case of "relatively low" temperatures and generally when the equilibrium free-carrier density n0 satisfies the Sablicov's, Vasil'ev, and Sandomirskii inequality. In this work an extensive computational study of this inequality in the temperature range of 300–1000 K was performed and a precise "map" is given concerning the violation of the inequality under various conditions including modulation frequency (0.1–106 Hz) and doping concentration (intrinsic to 1020 cm−3). Some experimental photomodulated measurements have been performed in order to test the validity of the "map." © 2002 American Institute of Physics.
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  • 82
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1274-1279 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Spectroscopic properties and room-temperature persistent spectral hole burning mechanisms of Eu3+-doped borate glasses were investigated. The depth of the burnt hole increased with the amount of carbon powders (i.e., degree of reducing atmosphere). This was attributed to the formation of defects which can donate free electrons for the photoreduction of Eu3+→Eu2+. Holes survived 〉104 s at 20 K and approximately 40% of hole areas were preserved after annealing at 280 K. The photoreduction of Eu3+ to Eu2+ is a primary mechanism of hole burning and this hypothesis was supported by spectral hole properties, relaxation properties as well as changes in the local structure of Eu3+ in glasses. © 2002 American Institute of Physics.
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  • 83
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1292-1297 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Cuprous oxide quantum particles as small as 2 nm (comparable to the Bohr exciton radius) were synthesized using an electrochemical route. Quantum confinement effects are evident from a blueshift in the optical absorption. The optical absorption spectra of Cu2O nanoparticles of different sizes are discussed. Structural analysis by x-ray diffraction as well as electron diffraction shows the nanoparticles to be cubic and single phased Cu2O. X-ray photoelectron spectroscopic studies indicate the presence of CuO on the surface of Cu2O core nanoparticles. © 2002 American Institute of Physics.
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  • 84
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1286-1291 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A catalyst powder was prepared by adsorption precipitation of iron acetate on a SiO2 support at a controlled pH. The selective reduction of this powder in a N2/C2H2 atmosphere at 700 °C generates multiwall carbon nanotubes. The study by x-ray diffraction and Mössbauer spectroscopy of the catalyst and reduced powders reveals that hematite particles with a 8–20 nm size range are involved in the formation of these carbon nanotubes and end up as Fe3C after the catalysis process. Moreover, coalescence upon reduction produces large particles responsible for the formation of a minor proportion of large tubes of the order of 100 nm in diameter. © 2002 American Institute of Physics.
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  • 85
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1298-1306 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The impact of metal–oxide–semiconductor processing on strained Si/SiGe device structures has been examined. Material was grown by gas-source molecular beam epitaxy and ultra low pressure chemical vapor deposition, with different as-grown surface roughness. The effects of RCA cleaning, gate oxidation and rapid thermal annealing on this material were studied by atomic force microscopy (AFM) and optical profilometry. Certain processes caused reactions common to both material types, whereas others yielded dissimilar responses. Filtering AFM roughness data of specific wavelengths enabled the effects of processing on large-scale surface roughness dominated by the cross-hatching morphology and smaller scale microroughness to be investigated. The results suggest that as-grown Si/SiGe material quality is not a good indicator of processed device performance, rather morphological changes which occur during processing must be considered. © 2002 American Institute of Physics.
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  • 86
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1337-1343 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Bi1−xSbx (x(approximate)0.1) alloy crystals present a high thermoelectric figure of merit at T(approximate)100 K. The alloys are difficult to grow successfully and require special techniques to avoid constitutional supercooling and the resulting segregation. We present a study of the growth of 200 nm wire arrays of Bi–Sb by high-pressure injection of the melt of the alloy in a porous template. We find that the concentration of Sb in the nanowires is much lower than the composition of the starting alloy and discuss the results in terms of a model of constitutional supercooling in restricted geometries. © 2002 American Institute of Physics.
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  • 87
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1317-1328 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electron spin resonance studies have been carried out on the isothermal passivation kinetics in 1 atm molecular H2 of trivalent Si traps (Pbs;Si3(Triple Bond)Si•) at the interface of thermal (111)/Si/SiO2 as a function of oxidation temperature Tox in the range 250–1100 °C. Interpretation within the generalized simple thermal (GST) passivation model, based on first-order interaction kinetics, reveals a distinct increase in spread σEf in the activation energy for passivation Ef with decreasing Tox (∼3 times in the covered Tox window), while the other key kinetic parameters (Ef, preexponential factor) remain essentially unchanged. The variation in σEf is ascribed to differently relaxed interfacial stress, affecting the spread in Pb defect morphology. In a second analytic part, the impact of the variation in Ef, and correlatively in the activation energy Ed for PbH dissociation, on Pb–hydrogen interaction kinetics is assessed within the GST-based full interaction scheme, describing parallel competing action of passivation and dissociation. In particular, the passivation behavior in 1 atm H2 of an initially exhaustively depassivated Pb system, is analyzed exposing, as a major result, that growing spreads σEf, σEd result in a drastic reduction in passivation efficiency (drop by four orders of magnitude for a threefold increase in σEf). For σEf/Ef(approximately-greater-than)20%, the Pb system cannot be inactivated beyond the 90% level, incompatible with device quality requirements. Heating time/temperature vs spread conditions for optimum passivation in H2 have been established, and the technological impact of altering σEf, σEd is discussed. At film edges and trench corners, which are vulnerable local regions of exces stress, and hence enhanced σEf, σEd, an edge defeat effect with respect to passivation is exposed. Within the relentless scaling of Si-based integrated circuit devices, the growing relative impact of edge regions may jeopardize proper passivation of interface traps in the conventional way in future device generations. © 2002 American Institute of Physics.
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  • 88
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    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied the influence of the carrier gas (hydrogen versus nitrogen) on the morphology and defect characteristics of GaN grown by epitaxial lateral overgrowth (ELO) using hydride vapor phase epitaxy (HVPE). Growth was carried out on metalorganic vapor phase epitaxy GaN/sapphire patterned with SiO2 stripes, aligned along the 〈11¯00〉 GaN direction. The cross sections of the ELO-grown stripes change from trapezoidal to triangular with an increase in hydrogen content in the carrier gas due to a change of the ratio of the growth velocities on the {112¯2} and (0001) facets. Transmission electron microscopy observations show that while in stripes with trapezoidal morphology, dislocations from the window region still reach the sample surface, for triangular stripes they are bent in the horizontal direction away from the top surface. Cross-sectional cathodoluminescence (CL) microscopy shows basically two distinct regions of luminescence intensity and nature, one showing near-band gap excitonic emission, the other a high intensity blueshifted emission band which we attribute to e–h plasma recombination, indicating a high local free carrier concentration due to intrinsic defects or impurities. These two regions are correlated with different growth facets and not with the dislocation distribution. An original two-step growth method was developed which exploits this dependence of the morphology on the gas phase composition. In the first step the formation of triangular facets is preferential. This is done to bend the dislocations which have propagated vertically from the seed layer into the horizontal direction. In the second step the layers are planarized using conditions which favor lateral growth. Very good control of the faceting and high reproducibility of the selectively grown structures and layers could be obtained. By using spatially resolved CL measurements carried out on cleaved cross sections of the layers, different domains could be identified and correlated with the growth mode. The ELO layers obtained by two-step growth have significantly reduced dislocation densities of around 2–3×107 cm−2 at the surface, which is comparable to the best values of HVPE ELO GaN reported in the literature. The full width half maximum of the x-ray rocking curve gives values below 200 arcsec. © 2002 American Institute of Physics.
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  • 89
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1344-1350 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this article we report the role of excess interstitials in the end-of-range region in transient enhanced diffusion of boron during annealing of laser-processed samples. The results show that although the amorphous layer in preamorphized silicon can be completely annealed by laser irradiation, the end-of-range damages were not sufficiently annealed. The end-of-range region contains a supersaturation of interstitial defects that enhance the diffusion of boron during a post-laser processing anneal. It is found that the transient enhanced diffusion is significantly suppressed when the melt depth is extended beyond the amorphous layer such that the interstitial dose in the region adjacent to the laser-melted layer is minimized. In this way, the abruptness of laser-processed ultrashallow junctions can be maintained upon further annealing at moderately high temperatures. Cross-sectional transmission electron microscopy shows that a virtually defect-free regrown layer is obtained by overmelting beyond the amorphous layer into the substrate. © 2002 American Institute of Physics.
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  • 90
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1351-1360 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The phase field microelasticity theory of a three-dimensional elastically anisotropic solid of arbitrarily inhomogeneous modulus also containing arbitrary structural inhomogeneities is proposed. The theory is based on the equation for the strain energy of the elastically and structurally inhomogeneous system presented as a functional of the phase field, which is the effective stress-free strain of the "equivalent" homogeneous modulus system. It is proved that the stress-free strain minimizing this functional fully determines the exact elastic equilibrium in the elastically and structurally inhomogeneous solid. The stress-free strain minimizer is obtained as a steady state solution of the time-dependent Ginzburg–Landau equation. The long-range strain-induced interaction due to the elastic and structural inhomogeneities is explicitly taken into account. Systems with voids and cracks are the special cases covered by this theory since voids and cracks are elastic inhomogeneities that have zero modulus. Other misfitting defects, such as dislocations and coherent precipitates, are also integrated into this theory. Examples of elastic equilibrium of elastically inhomogeneous solid under applied stress are considered. © 2002 American Institute of Physics.
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  • 91
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1361-1366 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The diffusion of indium in silicon has been investigated in the temperature range of 800 to 1000 °C by using secondary ion mass spectroscopy and transmission electron microscopy. Our data indicate that, for implants at 150 keV through a thin oxide layer (19 nm), the amount of dopant that leaves the silicon is only controlled by the flow of indium that reaches the surface, being both the segregation coefficient at the interface SiO2/Si and the indium diffusion coefficient in the oxide favorable to the out-diffusion. Comparison between experimental and simulated profiles has evidenced that, besides the expected transient enhanced diffusion occurring in the early phases of the annealing, a heavy loss of dopant by out-diffusion was associated with a high In diffusivity near the surface. Measurements of the hole concentration in uniformly doped silicon on insulator samples performed in the temperature range of 700 to 1100 °C indicate that indium solubility is equal or greater than 1.8×1018 cm−3; this value is higher than those previously proposed in literature. © 2002 American Institute of Physics.
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  • 92
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 3015-3020 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The analysis of the amplitude of the deep level transient spectroscopy signal due to DX centers is exploited to determine the EDX occupancy level of the DX center in Te-doped AlxGa1−xSb in the range of low values of x where EDX is resonant with the conduction band. We take advantage of a small but still detectable change in the occupancy factor of the DX level induced by the filling pulse. It is shown that EDX is very close to the L conduction band edge for x≤0.20. This behavior is different from the one at x≥0.30 where EDX lies in the forbidden energy gap and exhibits an x dependence similar to the X edge. These results are discussed at the light of different atomic configuration for DX centers at an anion-substitutional impurity. © 2002 American Institute of Physics.
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  • 93
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 3037-3043 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A mathematical-physical model to describe the charge transport across grain boundaries in p-type SrTiO3 ceramics in the low-temperature regime for arbitrary dc voltage steps has been developed. The finite element model structure consists of a one-dimensional cross section through a ceramic scenario. Mathematical formulation comprises a coupled system of continuity equations (utilizing Maxwell-Boltzmann transport equations) and Poisson's equation, with the appropriate boundary conditions for a potentiostatic simulation approach. The edges of the model are assumed to be blocking for ionic transport, and penetrable for electronic transport. The model was implemented exploiting routines from the numerical class library DIFFPACK™. After an initial electrostatic simulation a dc bias voltage step is applied. The evolution of the spatial profiles of electric potential, defect concentrations, space-charge density, and electric conductivity, and the current response are calculated. The results for the ceramic model structure confirm the experimentally observed Debye relaxation, and the characteristic dependence of long-term conductivity on the dc bias after space-charge polarization, before the onset of resistance degradation. © 2002 American Institute of Physics.
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  • 94
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 3054-3061 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A quantum dot (QD) can be formed at the intersection of the symmetric or asymmetric L-shaped (LQW) or T-shaped quantum wire (TQW). The bound state energies in such QD systems surrounded by inhomogeneous magnetic fields are found to depend strongly on the asymmetric parameter α=W2/W1, i.e., the ratio of the arm widths and magnetic field applied on the wire arms. Two effects of the magnetic field on the bound state energy of the electron can be obtained. One is the depletion effect which purges the electron out of the QD system. The other is to create an effective potential due to the quantized Landau levels of the magnetic field. Depletion effect is found to be more prominent in weak field region. Our results show the bound state energy of the electron in such QD system depends quadratically (linearly) on the magnetic field in the weak (strong) field region. It is also found that the bound state energy of the electron depends on the magnetic field strength only and not on its direction. A simple model is proposed to explain the behavior of the magnetic dependence of the bound state energy of the electron both in weak and strong magnetic field regions. The contour plots of the relative probability of the bound state in LQW or TQW in magnetic field are also presented. © 2002 American Institute of Physics.
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  • 95
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 3255-3260 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thermal stability of stacked self-assembled InP quantum dots (QDs) embedded in Ga0.51In0.49P (GaInP) under ex situ rapid thermal annealing (RTA) is studied by photoluminescence spectroscopy and quantitative high-resolution electron microscopy. It is found that InP QDs intermix with surrounding GaInP, and that this is enhanced with increasing temperature and duration of RTA. The preferential direction of the intermixing and reshaping of the QDs changes at different stages of RTA. This anisotropy is attributed to strain-assisted interdiffusion, and is expected in stacked QDs of other material systems. © 2002 American Institute of Physics.
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  • 96
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1598-1603 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using a combination of ultraviolet and x-ray photoelectron spectroscopies, we have studied the relative energy level alignment of two phosphorescent guest molecules, 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphine platinum (PtOEP) and tris(2-phenylpyridine)iridium (Ir(ppy)3), doped in an electron transport host, tris(8-hydroxyquinolinato) aluminum (III) (Alq3), and in a hole transport host, 4,4′-bis(carbazol-9-yl)biphenyl. In each of the guest–host systems, we find that the vacuum levels of the guest and the host molecules align, and that the position of the highest occupied molecular orbital of the phosphorescent guest is independent of the guest molecule concentration (0.8%–56% by mass). The vacuum level alignment implies free movement of the Fermi level within the gaps of the guest and the host molecules manifesting the intrinsic nature of these organic semiconductors. These results give insights into the role that the phosphorescent molecules play in trapping and transporting charges within the emissive layer of an organic light-emitting device. © 2002 American Institute of Physics.
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  • 97
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1588-1597 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a protocol for the consistent fabrication of glass cells to provide hyperpolarized (HP) 3He for pulmonary magnetic resonance imaging. The method for producing HP 3He is spin-exchange optical pumping. The valved cells must hold of order 1 atm⋅L of gas at up to 15 atm pressure. Because characteristic spin-exchange times are several hours, the longitudinal nuclear relaxation time T1 for 3He must be several tens of hours and robust with respect to repeated refilling and repolarization. Collisions with the cell wall are a significant and often dominant cause of relaxation. Consistent control of wall relaxation through cell fabrication procedures has historically proven difficult. With the help of the discovery of an important mechanism for wall relaxation that involves magnetic surface sites in the glass, and with the further confirmation of the importance of Rb metal to long wall-relaxation times, we have developed a successful protocol for fabrication of 3He spin exchange cells from inexpensive and easily worked borosilicate (Pyrex) glass. The cells are prepared under vacuum using a high-vacuum oil-free turbomolecular pumping station, and they are sealed off under vacuum after ≥100 mg of distilled Rb metal is driven in. Filling of cells with the requisite 3He–N2 mixture is done on an entirely separate gas-handling system. Our cells can be refilled and the gas repolarized indefinitely with no significant change in their wall properties. Relaxation data are presented for about 30 cells; the majority of these reach a "40/40" benchmark: T1〉40 h, and 3He polarizations reach or exceed 40%. Typical polarization times range from 12 to 20 h; 20% polarization can be achieved in 3–5 h. © 2002 American Institute of Physics.
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  • 98
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1604-1607 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ultrashort pulse lasers have proven to have superior advantages over conventional continuous wave and long pulse lasers for ablation of thin metal films. Though several investigations have been carried out to understand the phenomena of ultrashort pulse laser machining, the effect of the beam polarization on ablation of thin metal films has been seldom investigated. In this article, we report our recent observations on how the shape of the machined feature and also the damage threshold of the material varies according to the polarization of the ultrashort pulse laser beam. Based on this we have explained how the polarization of the beam controls the laser cutting rate, kerf width, edge quality, and ablation depth of the ablated feature. © 2002 American Institute of Physics.
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  • 99
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1608-1612 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A technique of laser-pulse shaping was developed for low-emittance electron-beam generation in a photocathode radio-frequency (rf) gun. The emittance growth due to space charge and rf effects in the rf gun was experimentally investigated with square and gaussian temporal pulse shapes. It was found that the square pulse shaping was a useful tool for both the reduction of nonlinear space-charge force and the correction of linear space charge. The normalized transverse rms emittance at 1 nC was obtained to be 1.20 πmm-mrad for the square pulse shape with pulse length of 9 ps full width at half maximum. The emittance was measured as a function of the electron bunch charge and the laser-pulse length. © 2002 American Institute of Physics.
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  • 100
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1613-1618 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A precision polarimeter has been developed to measure the linear polarization degree of Rayleigh scattered light. Application is made to measurement of the linear depolarization spectrum of atomic Cs in the vicinity of the 6s 2S1/2→6p 2Pj resonance transition. For measurements in an ∼220 cm−1 range around the 6s 2S1/2→6p 2P3/2 resonance transition, the ratio of line strengths for the two resonance transitions has been found to be 2.003(52), in excellent agreement with other methods. © 2002 American Institute of Physics.
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