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  • 1985-1989  (22)
  • 1935-1939  (1)
  • 1
    Electronic Resource
    Electronic Resource
    The temperature dependence of contact resistivity of the Ge/Pd and the Si/Pd nonalloyed contact scheme on n-GaAs (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 1621-1625 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The temperature dependence of the contact resistance of the Ge/Pd and Si/Pd metalization scheme on n-GaAs was investigated. These two contact systems are based on solid-phase reactions, thus leading to nonspiking ohmic contacts to n-GaAs. The experimental results show that the ohmic behavior is likely due to both a highly doped surface n+ region and/or a small barrier at the interface. The origin of this small barrier and nonlinear current-voltage characteristics for certain samples are also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342954
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  • 2
    Electronic Resource
    Electronic Resource
    Nonalloyed ohmic contacts to n-GaAs by solid-phase epitaxy of Ge (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 942-947 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A low resistance nonalloyed ohmic contact to n-GaAs is formed which utilizes the solid-phase epitaxy of Ge through PdGe. Discussion focuses on the conditions necessary to attain low specific contact resistivity (∼10−6 Ω cm2 on 1018 cm−3 n-GaAs) and on the interfacial morphology between the contact metallization and the GaAs substrate. MeV Rutherford backscattering spectrometry and channeling show the predominant reaction to be that of Pd with amorphous Ge to form PdGe followed by the solid-phase transport and epitaxial growth of Ge on 〈100〉 GaAs. Cross-sectional transmission electron microscopy and lattice imaging show a very limited initial Pd-GaAs reaction and a final interface which is planar and structurally abrupt to within atomic dimensions. The presence of excess Ge over that necessary for PdGe formation and the placement of Pd initially in contact with GaAs are required to result in the lowest contact resistivity. The experimental data suggest a replacement mechanism in which an n+-GaAs surface region is formed when Ge occupies excess Ga vacancies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.339705
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Thermal stability of TiSi2 on mono- and polycrystalline silicon (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 243-246 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thermal stability of TiSi2 on mono- and polycrystalline silicon was investigated by cross-sectional transmission electron microscopy and high-resolution electron energy loss spectroscopy. Additional heat treatments after silicide formation result in a rough silicide/silicon interface, discontinuity of the metal silicide film, and a penetration of silicide into silicon/polycrystalline silicon substrates. Plausible explanations for these observations are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.337688
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  • 4
    Electronic Resource
    Electronic Resource
    Molecular beam photoelectron spectroscopy and femtosecond intramolecular dynamics of H2O+ and D2O+ (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 6928-6939 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The 584 A(ring) photoelectron spectra of supersonic molecular beams of H2O and D2O have been obtained with improved resolution. The spectroscopic constants of the X˜ 2B1 and A˜ 2A1 state ions, including ω01, x011, ω02, x022, and x012, are reported. For the first two electronic states of the ion, precise line splittings were evaluated with a least squares fitting procedure, employing sums of empirical instrument response functions and a linear background. A simulation of the vibrational manifolds of the B˜ 2B2 state ions with combination progressions in the symmetry-allowed modes ν1 and ν2 failed to reproduce the diffuse photoelectron bands observed for both H2O and D2O. Autocorrelation functions were calculated from the photoelectron bands of all three electronic states. The B˜ 2B2 state correlation functions exhibit ultrafast decay, occurring on a 10−14 s time scale. The ν2 motion appears to define the decay in the correlation function. This behavior supports a previously proposed B˜ 2B2–A˜ 2A1 curve-crossing model for the nonradiative relaxation of the B˜ 2B2 state ions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.451379
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  • 5
    Electronic Resource
    Electronic Resource
    Photoelectron spectroscopy and inferred femtosecond intramolecular dynamics of C2H+2 and C2D+2 (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 84 (1986), S. 3022-3031 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The 584 A(ring) photoelectron spectra of rotationally cold C2H2 and C2D2 were obtained with improved resolution, permitting the first three electronic states of the ions to be characterized in greater detail. Temperature-dependent studies led to a definitive assignment of the low intensity features in the X˜ 2∏u state, yielding ν4=837±12 cm−1 for C2H+2 and ν4=702±12 cm−1 for C2D+2. The ν5 origin of the Renner–Teller multiplet was identified. In the case of C2D+2, a Fermi resonance with this multiplet contributed intensity to the ν1 mode, facilitating its evaluation at 2572±16 cm−1. The C2h geometry of the A˜ 2Ag state was determined from the two previously unobserved bending progressions, assigned to ν4 and ν5B, and evaluated at 492±12 and 605±12 cm−1 for C2H+2 and 339±12 and 516±12 cm−1 for C2D+2, respectively. A more extensive vibrational progression than previously evident, comprised of irregular spectral features indicative of nonadiabatic effects, was observed for the B 2∑+u state. Autocorrelation functions were derived from the spectra for all three electronic states, and the two electronically excited states exhibit an ultrafast decay on a 10−14 s time scale. The A˜ 2Ag state decays within one period of bending vibration, while the B˜ 2∑+u state survives only 14 fs, corresponding to a single period of symmetric stretching motion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.450283
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  • 6
    Electronic Resource
    Electronic Resource
    Plasma production and heating in a tandem mirror central cell by radio-frequency waves in the ion cyclotron frequency range (1988)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 31 (1988), S. 3744-3753 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Plasma production and heating in the central cell of the Tara tandem mirror [Nucl. Fusion 22, 549 (1982); Plasma Physics and Controlled Nuclear Fusion Research, 1986, Proceedings of the 11th International Conference, Kyoto, Japan (IAEA, Vienna, 1987), Vol. 2, p. 251] have been studied. Using radio-frequency excitation by a slot antenna in the ion cyclotron frequency range (ICRF), plasmas with a peak β⊥ of 3%, density of 4×1012 cm−3, ion temperature of 800 eV, and electron temperature of 75–100 eV were routinely produced. The plasma radius decreased with increasing ICRF power, causing reduced ICRF coupling and saturation of the plasma beta. About 70% of the applied ICRF power can be accounted for in direct heating of both ions and electrons. Wave field measurements have identified the applied ICRF to be the slow, ion cyclotron wave. In operation without end plugging, the plasma parameters were limited by poor axial confinement and the requirements for maintenance of magnetohydrodynamic stability and microstability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.866893
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  • 7
    Electronic Resource
    Electronic Resource
    Stability of plasmas sustained by ion cyclotron wave excitation in the central cell of the Tara tandem mirror (1989)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 1 (1989), S. 851-861 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The stability of plasmas produced by radio-frequency heating in the ion cyclotron frequency range (ICRF) has been studied in the central cell of the Tara tandem mirror [Nucl. Fusion 22, 549 (1982); Plasma Physics and Controlled Nuclear Fusion Research 1986, Proceedings of the 11th International Conference, Kyoto (IAEA, Vienna, 1987), Vol. II, p. 251]. Ion cyclotron wave excitation by a slot antenna provided stability against macroscopic plasma motions in an axisymmetric configuration. The maintenance of macroscopic stability depended on the ICRF power, gas fueling rate, ion cyclotron resonance location, and ω/ωci at the antenna location. The ICRF ponderomotive force model is consistent with many of the observed stability features and predicts that the E+ component of the ion cyclotron wave was responsible for the stabilization. The Alfvén ion cyclotron microinstability was observed when the plasma β⊥ and anisotropy were sufficiently high. Magnetic probe measurements of the unstable mode identified it as an ion cyclotron wave and the instability threshold was within a factor of 2 of the theoretical value.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.859010
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  • 8
    Electronic Resource
    Electronic Resource
    Wide range magnetic electron spectrograph (1989)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 60 (1989), S. 1233-1238 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An electron spectrograph is described that covers electron energies from 400 eV to 200 keV with an energy resolution of 10%. This overlaps the range of electrostatic deflection devices at low energy and solid state detectors at high energy. The spectrograph uses magnetic deflection of the electrons to achieve energy separation and images the full range of energies on a single plane. The magnetic circuit uses the fringing field of two axially located magnets to attain the large energy range. Six separate electron beams can be dispersed in the field, each entering the circuit from a different angle. This is a particular advantage when measuring plasma electron three-dimensional velocity distributions. The angular response of the instrument is particularly favorable and the stray magnetic field is sufficiently low to meet spacecraft requirements. Compared with electrostatic deflection devices, the spectrograph is particularly advantageous for measuring high energy electron plasma velocity distribution functions with fast time resolution at modest energy resolution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1140296
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  • 9
    Electronic Resource
    Electronic Resource
    Radiation-induced formation of cavities in amorphous germanium (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 2494-2496 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Prethinned polycrystalline Ge TEM samples were irradiated with 1.5 MeV Kr+ ions at room temperature while structural and morphological changes were observed in situ in the Argonne High Voltage Electron Microscope-Tandem Facility. After a Kr+ dose of 1.2×1014 ions/cm2, the irradiated Ge was completely amorphized. A high density of small void-like cavities was observed after a Kr+ dose of 7×1014 ions/cm2. With increasing Kr+ ion dose, these cavities grew into large holes transforming the irradiated Ge into a sponge-like porous material after 8.5×1015 ions/cm2. The radiation-induced nucleation of void-like cavities in amorphous material is astonishing, and the final structure of the irradiated Ge with enormous surface area may have potential applications.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102009
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  • 10
    Electronic Resource
    Electronic Resource
    Low-resistance nonspiking ohmic contact for AlGaAs/GaAs high electron mobility transistors using the Ge/Pd scheme (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 2677-2679 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Nonspiking (nonalloyed) Ge/Pd ohmic contact formed via solid phase reaction on an AlGaAs/GaAs high electron mobility transistor (HEMT) was investigated. The surface morphology of the Ge/Pd contact is smooth and planar with a typical contact resistivity of about 3×10−7 Ω cm2. The current-voltage characteristics of the HEMTs with the Ge/Pd contacts are similar to those with the conventional AuGe/Ni spiking (alloyed) contacts. Since only a thin substrate surface layer of 100–200 A(ring) was reacted with the Ge/Pd contact, we can conclude that ohmic contacts can be made to the two-dimensional electron gas without deep penetration of the metallization. This observation is in agreement with the concept that transport due to tunneling is significant across heterojunctions. The Ge/Pd contact may be potentially useful in HEMT integrated circuit technology.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101032
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