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  • 1
    Electronic Resource
    Electronic Resource
    Plasma properties determined with induction loop probes in a planar inductively coupled plasma source (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 1298-1302 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electromagnetic fields in a planar rf inductively coupled plasma source, of interest for materials processing, were measured using a two-loop inductive (B-dot) probe. The two loops were oriented to measure the time derivative of the axial and radial components of the magnetic field B(overdot)z and B(overdot)r, respectively, at various positions in the r–z plane of the cylindrically symmetric argon discharge. Maxwell's equations were used with this data to calculate amplitudes of the rf azimuthal electric field Eφ and current density Jφ, as well as the complex permittivity ε of the plasma, from which the electron density ne was calculated. The electron densities calculated using this technique were found to compare favorably to the results of measurements made with Langmuir probes. Electron drift velocities calculated from Jφ and ne were found to be comparable to electron thermal velocities in the region of highest Eφ and thus may contribute to local enhancement of electron impact reactions, thereby affecting process chemistry and uniformity. The peak in the drift velocity moved radially outward as the pressure increased due changes in the radial plasma density profile. This technique is applicable to chemistries where Langmuir probes are not practical. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361025
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  • 2
    Electronic Resource
    Electronic Resource
    Intersubband all-optical limiter based on thermally induced intervalley transfer (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 7662-7665 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We propose an all-optical limiter based on the thermally induced intervalley transfer of electrons from Γ-valley states with forbidden normal-incidence intersubband interactions to L-valley states which absorb strongly. Detailed modeling of the device performance in the short-pulse regime (≤100 ns) yields that the output intensity for a limiter with only 10% insertion loss at low excitation levels will remain clamped over a dynamic range of 25–40.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.365344
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  • 3
    Electronic Resource
    Electronic Resource
    Infrared electroabsorption modulation at normal incidence in asymmetrically stepped AlSb/InAs/GaSb/AlSb quantum wells (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 92-96 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A normal-incidence modulation mechanism is proposed which uses the Stark effect to induce Γ-L transitions in asymmetrically stepped AlSb/InAs/GaSb/AlSb quantum wells (QWs). A significant feature of this structure is the unusual band alignments which localize two deep wells for the Γ and L bands in adjacent layers, i.e., the Γ-valley minimum is in the InAs while the L-valley minimum is in the GaSb. In contrast to a square QW, where the Stark shifts for both Γ and L subbands are in the same direction, the two step wells for Γ and L valleys in the proposed structure are oppositely biased in the presence of an electric field. Therefore, the first Γ and L subbands move toward each other, making the Γ-L crossover occur more efficiently. Near this point, most of the Γ electrons transfer to the L valleys, where they are allowed to make intersubband transitions under normally incident radiation. As a result, the device switches from being transparent to normal-incidence light to strongly absorbing it. The calculations indicate that excellent on/off ratios can be achieved in this structure operating at T≤150 K with electric fields on the order of ∼100 kV/cm for any infrared wavelength within the range of 3–20 μm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357065
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  • 4
    Electronic Resource
    Electronic Resource
    Quantitative mobility spectrum analysis of multicarrier conduction in semiconductors (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 709-713 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We demonstrate an optimized quantitative mobility spectrum analysis (QMSA) technique for determining free electron and hole densities and mobilities from magnetic-field-dependent Hall and resistivity data. The procedure is applied to an In1−xGaxAs–In1−xAlxAs single quantum well, GaAs–AlAs asymmetric double quantum wells, and Hg1−xCdxTe epitaxial thin films containing multiple carrier species. The results illustrate the reliability, versatility, and sensitivity of the analysis, which is fully computer automated following input of the magnetic-field-dependent data. QMSA is found to be a suitable standard tool for the routine electrical characterization of semiconductor material and device transport properties. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.364211
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  • 5
    Electronic Resource
    Electronic Resource
    Measurements of electromagnetic fields in a planar radio-frequency inductively coupled plasma source (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 90-96 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electromagnetic fields in a planar radio-frequency inductively coupled plasma source were measured using an inductive loop (B-dot) probe. The probe was oriented to measure the time derivative of the axial component of the magnetic field (B(overdot)z). Using these measurements and Faraday's law, taking advantage of cylindrical symmetry, the time varying azimuthal electric field (Eφ) was calculated directly. Contour plots of B(overdot)z and Eφ in the r-z plane show that the radio-frequency electromagnetic fields penetrate further into the plasma at lower gas pressure and lower rf power, corresponding to less effective shielding of the fields at lower plasma density. Estimates of skin depth from the axial decay of the field amplitudes near the axis of the discharge are consistent with values calculated from plasma parameters measured with Langmuir probes, confirming that near the axis the degree of shielding is most strongly dependent on the local plasma density. Near the conducting walls of the chamber, the skin depth calculations from the Langmuir probe data diverge from the B-dot probe data. B-dot probe measurements taken in the absence of plasma show that near the walls of the chamber the axial decay of the field amplitude is partly a geometrical effect in addition to a plasma shielding effect. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360585
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  • 6
    Electronic Resource
    Electronic Resource
    The effect of methane on photocurrents generated by exciting xenon below its first ionization potential (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 4628-4634 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Photocurrent excitation spectra of xenon and of the xenon–methane absorber–perturber system were studied in cells equipped with LiF windows cooled to ≈−30 °C. The cooling was needed to shift the LiF cutoff so as to enable measurements at photon energies up to the first ionization potential of Xe (12.13 eV). The spectra observed in methane–xenon mixtures were essentially similar to those in neat xenon, demonstrating that the Hornbeck–Molnar process (excitation of a xenon atom–excimer formation–ionization of an excimer) is feasible even in the presence of the molecular perturber CH4 at pressures up to ≈ 105 Pa. The primary effect of CH4 is to decrease the photocurrent, since photons in the energy range in question are absorbed by the methane molecules as well, without photoionizing them. The dependence of the current on methane concentration showed that the above mechanism is not the only one by which methane quenches the current. Moreover, the degree of quenching of the current by methane is dependent on the photon energy. The analysis of this dependence led to the assumption that an excited xenon atom and a methane molecule may form an excimer. Previous results on the Ar:Xe and Kr:Xe systems support this assumption. Peak inversions observed at high pressures in neat xenon, but absent in the CH4:Xe system, are discussed on the basis of prevailing models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467451
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  • 7
    Electronic Resource
    Electronic Resource
    Optimum growth parameters for type-II infrared lasers (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 1796-1799 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The surface, structural, and optical properties of InAs/InGaSb/AlSb mid-infrared lasers grown by molecular beam epitaxy have been systematically studied, respectively, by Nomarski differential interference contrast, high-resolution x-ray diffraction, and variable-temperature photoluminescence. It is found that the optimum growth temperature is between 400 and 450 °C, based on the calibrated transmission thermometry. In addition, the impact of interfacial bond type and Sb sources has been investigated. A 5.91 μm laser, grown with the optimal growth parameters, exhibits a maximum cw operating temperature of 210 K. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370971
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  • 8
    Electronic Resource
    Electronic Resource
    Computer-controlled system designed to measure photodegradation of photochromic compounds (1993)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 64 (1993), S. 1803-1808 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In this paper, we describe a new, entirely computer-controlled apparatus designed for degradation studies of photochromic compounds. Photodegradation can be performed in three different ways using, in addition to the usual flash mode, the cyclic and continuous modes which more closely simulate daylight exposure conditions. In each mode, the "fatigue resistance'' parameter is computed. Moreover, the spectrokinetic parameters of photomerocyanine species can be obtained from the kinetic mode. Due particularly to the fully computer-controlled experimental setup, the between-day reproducibility of the initial absorbance and fatigue resistance determinations are better than 4% and 6%, respectively. Owing to the modular design of the menu-driven software, written in C language, the apparatus is very flexible and easy to use.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1144014
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  • 9
    Electronic Resource
    Electronic Resource
    High-speed circuits for TE discharge lasers and high-voltage applications (1993)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 64 (1993), S. 839-853 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Pulsed transverse electric (TE) glow discharges used to produce population inversions in gas lasers at 1–20 atm require high-speed, high-voltage, high-current capacitor banks. In this article we first review and compare the circuits in common use to produce the required fast, self-sustained glow discharges in CO2, excimer, and N2 lasers. The parameters and circuit types given will be useful to future designers of pulsed gas lasers to design and to optimize any proposed circuit in order to yield any desired operating conditions and parameters. The n-stage circuit types presented are capacitor-transfer (C-C), L-C inversion, Marx bank, and fourfold L-C inversion, with their double-sided counterparts, and also their transmission-line counterparts, such as the Blumlein circuit. A one-parameter differential equation is developed which describes the general series C-L-R circuit. Electrical pulses measured on various lasers are compared with the differential equation solutions for various bank impedances and load resistances. We then present the design and measurements of a new automatically preionized, double-sided, L-C inversion circuit for an 800-mJ, TE CO2 laser, and compare it to previous systems. Methods to lengthen the discharge pulse, and some novel active mode locking techniques are discussed. We compare the L-C inversion circuit, the fourfold L-C inversion circuit, the conventional Marx bank, and the "double Marx bank'' for lasers and other applications, such as pulsed particle accelerators. Finally, we discuss capacitor bank interconnections, electro-optic probe systems, and various triggering methods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1144131
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  • 10
    Electronic Resource
    Electronic Resource
    Band parameters for III–V compound semiconductors and their alloys (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 5815-5875 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a comprehensive, up-to-date compilation of band parameters for the technologically important III–V zinc blende and wurtzite compound semiconductors: GaAs, GaSb, GaP, GaN, AlAs, AlSb, AlP, AlN, InAs, InSb, InP, and InN, along with their ternary and quaternary alloys. Based on a review of the existing literature, complete and consistent parameter sets are given for all materials. Emphasizing the quantities required for band structure calculations, we tabulate the direct and indirect energy gaps, spin-orbit, and crystal-field splittings, alloy bowing parameters, effective masses for electrons, heavy, light, and split-off holes, Luttinger parameters, interband momentum matrix elements, and deformation potentials, including temperature and alloy-composition dependences where available. Heterostructure band offsets are also given, on an absolute scale that allows any material to be aligned relative to any other. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1368156
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