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  • American Institute of Physics (AIP)  (127)
  • Oxford University Press  (51)
  • 1990-1994  (165)
  • 1980-1984  (13)
  • 1
    Publication Date: 1992-01-01
    Print ISSN: 0964-6906
    Electronic ISSN: 1460-2083
    Topics: Biology , Medicine
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 4486-4487 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The Schottky barrier of Na deposited onto ultrahigh vacuum cleaved p-type GaP has been determined by in situ current-voltage measurements. The Schottky barrier height of 1.10 eV for this low work function metal contacts is consistent with a general weak metal dependence for barrier formation on GaP(110).
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 1548-1552 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A study has been made of the effect of hydrostatic pressure on an AlAs/GaAs/AlAs resonant tunneling diode in which the electrodes have been deliberately asymmetrically doped. In reverse bias, current is injected into the structure from a highly doped n+-GaAs electrode and in forward bias from a two-dimensional accumulation layer at the GaAs/AlAs interface. When large hydrostatic pressures are applied at 77 K, regions of negative differential resistance are induced in both bias directions. Current maxima with peak-to-valley ratios as large as 4 have been measured at 8 kbar. The intrinsic asymmetry of the structure aids in the identification of the origins of these features in terms of the X-point conduction-band minima of the device.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 2346-2350 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Transmission and reflection measurements in the energy range 0.5–1 eV have been performed on thin CoSi2 films grown by molecular-beam epitaxy on Si(111). For film thicknesses above 200 A(ring), the transmission factor decreases exponentially with film thickness, with an optical attenuation length of 180 A(ring) nearly independent of photon energy. Deviations from this law for film thicknesses below 200 A(ring) are explained by reflection effects. These data, supplemented by reflection measurements, can be fitted by theoretical calculations of the transmission and reflection factors, thus leading to the determination of the CoSi2 optical indexes. The energy dependence of the real and imaginary indexes is found to be consistent with the Drude model. Some interesting aspects of this intraband absorption either in ultrathin films or at low temperature are presented.
    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 67 (1990), S. 4167-4172 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin-film polycrystalline CdTe was electrodeposited as described previously onto indium-tin-oxide coated glass under argon and then stored either under argon or air before and after the annealing step. Dopants were incorporated into films by several methods. Indium, Cadmium, and silver were introduced into the films either by codeposition or by electromigration techniques as described previously for copper, and the doping process was followed by heat treatment. Tellurium was introduced into two films by heating the samples in a tellurium atmosphere, and the effect of oxygen on the CdTe was investigated by a high-temperature heat treatment in air. The effect of these doping procedures on the conductivity was investigated at various temperatures. For this purpose, a system was built to measure extremely high resistances (〉1012) over a large and well-controlled temperature range. Because of the polycrystalline nature of the films, the results are discussed in terms of a model in which the conducitivity is affected by the density of grain boundary states.
    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 70 (1991), S. 6732-6742 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A method is presented to deduce central ion temperature and toroidal rotation velocity from line-of-sight averaged x-ray spectra from hot plasmas. The analysis is based on atomic data for the processes that give rise to x-ray spectral lines. Combined with measured electron temperature and density profiles a synthetic spectrum is calculated. The fit of this synthetic spectrum to the observed one gives a new level of accuracy to line-of-sight integrated observations in a considerably extended range of ion temperatures and toroidal rotation velocities. The choice of model for radial profiles for ion temperature and toroidal rotation velocity is shown not to be critical. The concentration of the emitting impurity is deduced from the total line intensity, making use of the absolute calibration of the detector sensitivity. The effective plasma charge Zeff is derived from the absolute level of the continuum radiation. These measurements are based on atomic data for x-ray line and continuum radiation and measured electron temperature and density profiles. The results for ion temperature and toroidal rotation velocity obtained by this analysis are compared with those from visible charge exchange spectroscopy. The observed visible lines are shifted in wavelength, and their width is reduced, due to the velocity dependence of the cross section for the charge transfer from the neutral beam particles to the observed impurities. The theoretically predicted magnitude of these effects is verified. When the results from visible charge exchange spectroscopy are corrected for the cross-section effects, excellent agreement of central ion temperature and rotation velocity with the results of this new analysis is obtained.
    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 70 (1991), S. 1847-1849 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Stress waves were generated in sections of human vascular tissue by transmitting laser pulses from a XeCl laser source through a glass fiber. Needle-type polyvinylidenefluoride hydrophones were used to detect the acoustic response of the tissue samples during ablation. The experimental arrangement allowed the discrimination in vitro between calcified hard tissue and normal arterial wall immersed in normal saline solution. Atheromatous vessels exhibited a shorter rise time and a higher peak stress than normal tissue.
    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 69 (1991), S. 3641-3645 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A theoretical study of thermally activated currents across AlxGa1−xAs barriers is presented, where x is varied from zero to one. By increasing the Al content, AlxGa1−xAs changes from a direct to an indirect band-gap semiconductor. Previous experiments on activated transport have shown that this crossover strongly affects the transport properties. However, usually these experiments are analyzed in terms of the classical Richardson law, which completely fails to explain the prefactor for high Al concentrations which drops by three orders of magnitude. A model is presented that describes the transport by considering two competing channels, one via the Γ minimum and the other via the longitudinal X minimum. The current flow through each channel is evaluated by calculating the transmission coefficient separately for the Γ and X barriers. This model gives new insights into the interpretation of the experimentally measured activation energy and the prefactor.
    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 67 (1990), S. 4385-4387 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The introduction rate of a hydrogen-related bistable electron trap, formed by a 150 °C plasma annealing, depends strongly on thermal preannealing. A pure thermal 850 °C preanneal completely anneals the native defects EL6 and EL3, reduces the native defect concentration EL2 by a factor of 10, and decreases equally the introduction rate of the bistable defect by a factor of 10. From a comparison between the profiles of these defects, it is possible to get informations on the microscopic structure of this hydrogen related defect as well as on the EL2 defect.
    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 73 (1993), S. 3220-3236 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin epitaxial single-crystalline B-type CoSi2 films (twin-oriented) have been grown in ultrahigh vacuum by stoichiometric codeposition of Co and Si on slightly misoriented (0.1°–0.3°) Si(111) substrates. The microstructure as well as the nature of interfacial defects has been investigated in detail by transmission electron microscopy. The defect structure is found to depend closely on the initial deposition parameters, annealing temperature, and the topography of the Si substrate. It will be shown that even during the early stages of layer growth, loss of coherence is obtained and lattice strain already starts to occur with the introduction of misfit dislocations with Burgers vector b=a/2〈110〉 inclined to the interface or with Burgers vector b=a/6〈112〉 parallel to it. It is demonstrated that ultrathin CoSi2 films with thickness of about 1 nm grown on slightly misoriented substrates with parallel surface steps, exhibit quite different defect structures at annealing temperatures between 300 °C and 550 °C. Control of the dislocation density has been obtained by applying a two-step growth procedure. CoSi2 layers grown to a thickness 〈hc (4–5 nm) exhibit line defects with Burgers vector b=a/6〈112〉 associated with interfacial misorientation-related steps. Above this thickness additional dislocations in the three equivalent directions are formed, indicating biaxial strain relaxation. In addition, calculations of the critical thickness hc of biaxial strain relaxation based on thermodynamic equilibrium theory are presented. It is shown that the observed critical thickness hc is in qualitative agreement with theoretical predictions.
    Type of Medium: Electronic Resource
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