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  • 1
    Electronic Resource
    Electronic Resource
    Isochronal annealing of local vibrational modes in proton- and deuteron-implanted InP (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 78-83 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have performed isochronal annealing experiments on the hydrogen-related local vibrational modes (LVMs) created by proton and deuteron implantation of InP. Implanted samples were annealed in 50 °C increments in the 200–600 °C temperature range for 30 min each and then measured by infrared absorption. A group of four different LVMs is observed, each of which arises from the hydrogen-phosphorus stretching vibration with different defects or impurities at nearest-neighbor sites. Each LVM exhibits an annealing behavior that is different than any of the other LVMs. The annealing results are shown and discussed in relation to the possible microscopic structure of the defect responsible for each LVM.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353832
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  • 2
    Electronic Resource
    Electronic Resource
    Local mode spectroscopy of proton- and deuteron-implanted InP (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 4805-4808 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have introduced hydrogen into single crystal InP:Fe by implanting samples with 2 MeV protons and/or deuterons at fluences between 1×1016 and 5×1017 cm−2. This results in the creation of four local vibrational modes (LVMs) in infrared absorption which are all due to the stretching vibration of bonds formed between phosphorous and the implanted atom with various lattice defects or impurities at nearest-neighbor sites. Our implant-created LVMs are much sharper than those reported by previous workers and we observe two additional well separated peaks. The two main LVMs show a strong fluence dependence and are probably associated with lattice defects. The two weakest LVMs are not as fluence-dependent and may be associated with impurities. Two samples were implanted with both protons and deuterons in an attempt to observe the formation of complexes containing both isotopes, but no evidence of such complexes could be found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350621
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  • 3
    Electronic Resource
    Electronic Resource
    Response to: "Comment on ‘The effect of charge state on the local vibrational mode absorption of the carbon acceptor in semi-insulating GaAs' '' (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 6733-6734 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In a previous report we showed the effect of photoquenching the EL2 donor in GaAs on the carbon acceptor electronic absorption and local vibrational mode (LVM) absorption spectra. We agree that for the sample used to illustrate these effects, only a small portion (9% or less) of the total carbon was neutralized by the photoquench. Other samples have been studied, however, in which a much larger fraction (30% or more) of the carbon has been neutralized with no effect on the carbon LVM. We therefore maintain that our previous conclusion, i.e., a change in the charge state of carbon has no significant effect on the LVM structure, is still valid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348899
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  • 4
    Electronic Resource
    Electronic Resource
    The effect of charge state on the local vibrational mode absorption of the carbon acceptor in semi-insulating GaAs (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 2504-2506 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We use infrared absorption spectroscopy to study both the electronic excitation and the local vibrational mode (LVM) of the carbon acceptor in semi-insulating GaAs as a function of EL2 photoquenching. The behavior of the far-infrared electronic lines shows that the normally compensated carbon becomes neutralized (i.e., changes its charge state from singly negative to neutral) when the EL2 absorption is photoquenched. At the same time, the LVM absorption band shows no change in spectral form or vibrational frequency of its fine structure after photoquenching which indicates that, contrary to expectations, a charge-state change has no measurable effect on this band.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346516
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  • 5
    Electronic Resource
    Electronic Resource
    ZnGeP2 grown by the liquid encapsulated Czochralski method (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 4030-4037 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The growth of ZnGeP2 by the liquid encapsulated Czochralski method is reported for the first time herein. Large boules of ZnGeP2, with diameters up to 40 mm and weights up to 400 gm were grown by Czochralski pulling from B2O3 encapsulated melts under high pressure (20 atm Ar) using axial gradients ≤120 °C/cm. Boules pulled at ≤4 mm/h exhibited large (50×20×15 mm3) monocrystalline grains of α-phase ZnGeP2 with room temperature electrical properties of p-type conduction, carrier concentrations ranging from 1012 to 1016 cm−3, and mobilities of 20 cm2/V s or less. Optical samples exhibited broad IR transmission (0.7 to 12.5 μm), second harmonic generation at 4.7 μm with 7.2% conversion efficiency, a broad subband gap photoluminescence signature, and near band-edge absorption similar to that observed in Bridgman-grown ZnGeP2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352870
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  • 6
    Electronic Resource
    Electronic Resource
    Determination of chemisorption geometries for complex molecules by using near-edge x-ray absorption fine structure: Ethylene on Ni(100) (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 5335-5341 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have derived theoretical expressions for the incident beam angular dependence of the absorption cross section for ethylene chemisorbed on single crystal surfaces with linearly polarized light. The changes in the π and σ resonance intensities for C 1s near-edge x-ray absorption fine structure (NEXAFS) spectra can be related to the geometry of chemisorption relative to the surface. The derived equations have been used to analyze experimental data in order to determine the structure of chemisorbed ethylene on Ni(100). At low temperatures ethylene bonds with the molecular axis parallel to the surface but with the molecular plane tilted 50°. The geometry of vinyl fragments formed by annealing the crystal to 180 K was also determined. The C–C bond is bent 35° from the surface normal in this case, with the plane of the molecule tilted by 65°.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455625
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  • 7
    Electronic Resource
    Electronic Resource
    Direct measurement of ZnGeP2 birefringence from 0.66 to 12.2 μm using polarized light interference (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 5942-5945 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The birefringence (Δn) of ZnGeP2 has been measured directly from polarized light interference spectra obtained in transmittance over the 0.66–12 μm wavelength range from samples of six different thicknesses. The Δn values were determined from the positions of fringe maxima (Δn=kλ/t) and then compared to previously published data which were obtained by a different technique. It was found that the interference fringe method results in values of Δn accurate to ±0.00005. The data are shown to exhibit much less scatter as a function of wavelength than previous results and can lead to more accurate calculations of phase-matching angles for second-harmonic generation applications. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359175
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of oxygen partial pressure during postheat treatment on Bi2Sr2CaCu2Oy/Ag tapes (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 331-335 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Effects of oxygen partial pressure PO2 during low temperature postheat treatments on the superconducting properties of silver-sheathed Bi2Sr2CaCu2Oy tapes were investigated. The critical temperature Tc of the resulting tapes changes systematically with PO2. This variation of Tc is attributed to the change of electronic carrier (hole) concentration by the observation of oxygen K-edge absorption spectra. The intragranular critical current density Jc is essentially unaffected by the heat treatment, while deterioration in grain connectivity is observed in the specimens treated in reduced-oxygen atmospheres. The change of anisotropy in Jc with respect to crystallographic orientations is also quite small for the variation of PO2. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362824
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  • 9
    Electronic Resource
    Electronic Resource
    Incorporation of carbon in heavily doped AlxGa1−xAs grown by metalorganic molecular beam epitaxy (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 294-296 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Hole concentrations in excess of 1020 cm−3 have been achieved in AlxGa1−xAs using carbon doping during metalorganic molecular beam epitaxy. Hall and secondary-ion mass spectrometry measurements show a 1:1 correspondence between the hole density and carbon concentration in as-grown samples, although post-growth annealing at 900 °C leads to a reduction in the net free-carrier concentration (typically a decrease of ∼40% for 30 s anneals). The carbon-localized vibrational modes (LVMs) show fine structure due to the presence of three different symmetries for substitutional carbon CAs, namely Td, C2v, and C3v. The experimental CAs LVM line positions are in remarkable agreement with the predictions of a rigid ion model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103718
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  • 10
    Electronic Resource
    Electronic Resource
    Observation of the second energy level of the EL2 defect in GaAs by the infrared absorption technique (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 864-866 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The second energy level of the EL2 defect (EL2+/++ ) is observed by using the infrared absorption technique and monochromatic light irradiation in undoped and lightly alloyed unannealed bulk GaAs. The EL2+/++ spectrum exhibits a complex structure and it does not exist in annealed samples. The EL2+/++ →EL20/+ and EL20/+ →EL2+/++ transitions were obtained by illuminating the samples with 0.7≤hν≤0.95 eV and 1.3≤hν≤1.5 eV, respectively. The transformation EL2+/++ ↔EL20/+ can be achieved in less than 10 s and can be repeatedly switched back and forth between the two states.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101623
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