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  • 1
    Electronic Resource
    Electronic Resource
    Depolarization ratios of resonance Raman scattering in the gas phase (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 4125-4143 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: All three scattering invariants, isotropic, antisymmetric, and anisotropic, contribute to the resonance Raman (RR) activity of randomly oriented gas phase scatterers as shown in a sum-over-all-rovibronic-states approach regardless of the symmetry of the vibrational transition. Thus, in the gas phase, totally symmetric modes may have Raman depolarization ratios (ρ)〉3/4 and nontotally symmetric modes may have ρ≠3/4 for resonance excitation frequencies. Large ρ dispersion effects are predicted when the RR scattering cross section is dominated by the contribution of a single vibronic band. The extent of this purely rotational effect sensitively depends on the excitation frequency and the resonant dephasing rate. These depolarization ratio effects are demonstrated by the resonance Raman scattering of CH3I (B state) and NH3, ND3 (A state) for both a and e vibrational bands as well as for J (NH3) and K (CH3I) resolved rovibrational features.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455771
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  • 2
    Electronic Resource
    Electronic Resource
    Rovibrational Raman scattering of CH3I vapor: Resonance with a perpendicularly polarized electronic transition (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 4115-4124 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The Raman scattering due to resonance with a perpendicularly polarized electronic transition of a symmetric top molecule in the gas phase is described in a sum-over-all-states approach. The derived intensity and depolarization ratio expressions in an irreducible two-photon tensor basis are applied to the analysis of the ν2 (a1 ) and ν6 (e) bands of CH3 I derived from resonance with the predissociated X→B absorption system. A lifetime of 0.5±0.1 ps is determined for the electronic origin and several K-specific rovibronic levels of the v'6 =1 band of the resonant excited state. These results are contrasted with recent dynamical interpretations of the corresponding jet-cooled CH3 I absorption spectra.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455770
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  • 3
    Electronic Resource
    Electronic Resource
    Two-dimensional hole gas in Si/Si0.85Ge0.15/Si modulation-doped double heterostructures (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 2701-2703 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Si/Si0.85Ge0.15/Si p-type modulation-doped double heterostructures have been grown by the ultrahigh vacuum/chemical vapor deposition technique, and mobility enhancement has been observed at low temperatures. For heterostructures with Si layers doped with boron to ∼1×1019 cm−3, hole mobilities of ∼900 cm2/V s at 14 K have been obtained. No carrier freeze-out behavior has been observed at low temperatures. The existence of two-dimensional hole gas was determined by the tilted-field Shubnikov–de Haas measurement. Both Si/SiGe and SiGe/Si heterointerfaces were found to be equivalent and of excellent interfacial quality. The valence-band maximum of Si0.85Ge0.15 alloy has been estimated to be (approximately-equal-to)0.95 meV higher than that of Si. A hole effective mass of 0.44±0.03m0, which is consistent with the interpolation of the bulk band structures for the Si0.85Ge0.15 alloy, has been obtained for the heterostructure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101019
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  • 4
    Electronic Resource
    Electronic Resource
    High hole mobility in Si/Si1−xGex/Si p-type modulation-doped double heterostructures (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 2333-2335 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High quality Si/Si1−xGex/Si p-type modulation-doped double heterostructures with x=0.12 and 0.15 have been grown by the ultrahigh vacuum/chemical vapor deposition technique. Hole mobilities as high as ∼3700 cm2/V s at 14 K have been obtained for heterostructures with x=0.12, at a sheet carrier concentration of ∼8×1011 cm−2. This is the highest hole mobility ever reported for p-type Si material at these carrier concentrations. The electrical properties of these heterostructures at low temperatures are those expected of a two-dimensional hole gas at Si/SiGe and SiGe/Si heterointerfaces. The high hole mobility is indicative of excellent interfacial properties. Peak mobilities were observed to depend on the level and proximity of remote B dopant species, as well as the Ge content of the alloyed layers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102274
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  • 5
    Electronic Resource
    Electronic Resource
    Thermal and electrical properties of tetrakis(alkylseleno)tetrathiafulvalenes (TSeCn-TTF, n = 1-18) (1989)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 93 (1989), S. 5947-5952 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100352a058
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  • 6
    Electronic Resource
    Electronic Resource
    Controlled carbon doping of GaAs by metalorganic vapor phase epitaxy (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 1317-1319 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The controlled incorporation of carbon has been demonstrated for the metalorganic vapor phase epitaxy of GaAs. Carbon levels between 1016 and 1019 cm−3 can be achieved under typical growth conditions by using Ga(CH3)3 and either As(CH3)3 or mixtures of As(CH3)3 and AsH3. The carbon incorporation into GaAs goes through a minimum with growth temperature at ∼650 °C when using Ga(CH3)3 and As(CH3)3. The controlled addition of AsH3 monotonically decreases the carbon incorporation. The high carbon levels ((approximately-greater-than)1–2×1019 cm−3), greater than the reported solid solubility, are thermally stable with a low diffusion coefficient. The GaAs:C layers exhibit a low deep level concentration, ∼1013 cm−3, with only a single midgap trap present.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100008
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  • 7
    Electronic Resource
    Electronic Resource
    Electrical characterization of GaAs/Al0.30Ga0.70 As p+-n heterojunctions grown by metalorganic vapor phase epitaxy (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 4928-4935 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electrical transport measurements are very sensitive to the structure of a heterojunction. This sensitivity is used in conjunction with a realistic model for the band diagram to determine the position of the dopant junction relative to the metallurgical junction. This electrical technique involves the determination of an effective barrier height from temperature-dependent I-V measurements and comparison with calculated barrier heights. The sensitivity of the electrical characteristics to the device structure can often be greater than that of secondary ion mass spectroscopy or C-V profiling. GaAs/Al0.30Ga0.70 As p+-n heterojunctions grown under a variety of conditions are used to demonstrate this technique. Growth conditions which produce abrupt zinc profiles are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343209
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  • 8
    Electronic Resource
    Electronic Resource
    Deep levels in p-type GaAs grown by metalorganic vapor phase epitaxy (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 4975-4986 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report a detailed deep level transient spectroscopic study in p-type Mg- and Zn-doped GaAs epitaxial layers grown by metal-organic vapor phase epitaxy. Dependence of deep level structures on doping concentrations and growth temperatures has been investigated. Over a wide range of growth conditions, four hole traps and an electron trap ranging in activation energy from 0.18–0.79 eV were measured in GaAs:Mg while only a single hole trap has been observed in GaAs:Zn.The presence of a certain trap and its concentration in GaAs:Mg depends mainly on the doping concentration in the layers. The total trap concentration in the GaAs:Mg decreases rapidly with doping concentration for p〉4×1017 cm−3. The physical and chemical origins of several of these traps have been identified. The Mg-doped GaAs always exhibited a greater concentration of midgap trap levels than the Zn-doped material, regardless of dopant concentration or growth temperature. The overall defect structure and dopant incorporation characteristics indicate that Zn is the preferred dopant species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342447
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  • 9
    Electronic Resource
    Electronic Resource
    Substituting low-energy (〈30 eV) ion bombardment for elevated temperature in silicon epitaxy (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 6754-6760 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Normally required high substrate temperature for achieving epitaxial film growth can be replaced by low-energy (〈30 eV), high-current-density (∼1 mA/cm2) ion bombardment during film deposition. For this a Si substrate wafer was immersed like a large negative Langmuir probe in a low-pressure (5×10−4 Torr) mercury vapor plasma while receiving Si atoms sputtered from a Si wafer target. The Hg plasma was created by extracting a 4-A discharge current at 25-V discharge voltage from a Hg cathode spot on a liquid-Hg pool. Electron channeling patterns proved that uniform Si spitaxial films can be obtained over the whole substrate wafer area at temperatures not exceeding 300 °C. The best epitaxial films were obtained when the substrate is bombarded (by biasing) during deposition with 23-eV Hg ions. The electrical properties of the coatings indicated that the films were close, but not yet of device quality because of the impurities inherent in our non-ultrahigh-vacuum nonbakable Pyrex chamber pumped only with a 12-l/s Hg diffusion pump.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342008
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  • 10
    Electronic Resource
    Electronic Resource
    Studies of implanted iron in silicon by channeling and Rutherford backscattering (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 1336-1341 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Different amounts of 100-keV iron ions have been implanted into high-resistivity p-type FZ-silicon samples. The implantation damage, recovery of damage during various annealing periods and temperatures, movement of iron atoms under annealing and oxidation, and the kinds of defects created after implantation, annealing, or oxidation are all investigated by channeling and backscattering measurements. We have found that the critical fluence of 100-keV iron implanted into silicon at room temperature is ∼2.5×1014 Fe/cm2, and that iron atoms are gettered by silicon oxidation. In this supersaturated region iron atoms diffuse slightly towards bulk silicon during high-temperature annealing (≥1100 °C) but not at all during low-temperature annealing (≤1000 °C) in dry nitrogen ambient.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.337306
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