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  • American Institute of Physics (AIP)  (101)
  • 1990-1994  (101)
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  • 1990  (101)
  • 1
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The structure of defects occurring in degraded 1.3-μm double-channel planar buried heterostructure type laser diodes was studied in detail by conventional diffraction contrast, weak-beam dark-field microscopy and high-resolution lattice imaging in a transmission electron microscope. The electrical activity of the defects was analyzed by means of the electron-beam-induced current. Device degradation is associated with the presence of interstitial Frank partial dislocation loops with a Burgers vector of (a/3) {111} at the interfaces between the InGaAsP active layer exposed after the channel etching and the first p+-InP layer of the liquid-phase-epitaxy-grown current-blocking layers. No other types of defects were observed in the course of the present study. The implications of the latter finding are far-reaching and lead to a new degradation model for the microstrctural changes associated with the gradual degradation of long-wavelength lasers. A new degradation model is proposed, and laser diode design considerations for degradation-free operation are given. These consdierations are twofold: the device structure should (a) not favor Frank partial dislocation loop nucleation and (b) suppress the dissociation of the Frank partial dislocations.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 3709-3712 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A chevron-type Raman notch filter (RNF) set is described. lt combines a high signal throughput (up to 90% around 1600 cm−1 and (approximately-greater-than)80% between and 700 and 2700 cm−1) with a laser line suppression of 108–109. The filter set can be used to replace the first two dispersion stages in triple-stage Raman monochromators commonly employed in multichannel detection systems. This yields a gain in intensity of the detected Raman signal of a factor of 4. It is shown that in Raman spectrometers with a backscatter geometry, the filter set can also be used to optically couple the microscope and the spectrometer. This leads to a further increase in signal intensity of a factor of 3–4 as compared to the situation where a beam splitter is used. Additional advantages of the RNF set are the fact that signal throughput is almost polarization independent over a large spectral interval and that it offers the possibility to simultaneously record Stokes and anti-Stokes spectra.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 622-624 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: This article deals with an application of the technique of converting hydrogen atoms into negative ions on a low-work-function surface, which is similar to the method nowadays utilized in H− surface sources. This conversion technique is the basis for a time-of-flight spectrometer, for which a proof of principle has recently been established. The conversion takes place on a tungsten (110) crystal target that is covered with cesium. By mounting this target in the detector part of the spectrometer, this apparatus is made sensitive to hydrogen atoms that have energy in the range 10–1000 eV. This feature makes the spectrometer a very powerful and unique tool for detection of low-energy hydrogen atoms. It is, for instance, capable of detecting low-energy hydrogen atoms that are emitted from the edge of a tokamak plasma, and therefore it can yield information on the hydrogen recycling inside the tokamak and hence on the energy balance of the plasma. In the paper we discuss the principle of the detection method, along with a presentation of some time-of-flight spectra that have been obtained from a tokamak plasma.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 732-735 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A small optical device has been constructed to determine aerosol total area concentrations from angular scattering. Particles in the open sample volume are irradiated by a pulsed laser diode. Radiation scattered at angles between 15° and 35° is detected by a photodiode. The amplified signals are processed with a sample/hold circuit. This instrument has been applied for measurements on sea spray aerosol near the air-sea interface. Wave-induced fluctuations were clearly demonstrated. Other applications are indicated.
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 7568-7571 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: When left in air, as-grown anodic oxides grown under optimized conditions described in the literature have been found to age. It is shown that this is caused by a hygroscopic component in the outer indium-rich layer of the oxide film. When oxalic acid is present in the forming electrolyte, this phenomenon is not observed: As-grown oxides are stable and have a constant composition throughout their thickness. This paper discusses some of the properties of the oxide films, both as-grown and annealed, and some aspects of the chemistry of their formation. This distinct behavior of oxalic acid can be attributed to the fact that it forms soluble complexes with In(III) in the relevant pH range.
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 2264-2271 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this paper a study is made of the heat transfer inside cylindrical resistance diffusion and low-pressure chemical vapor deposition furnaces, aimed at developing an improved temperature controller. A model of the thermal behavior is derived which also covers the important class of furnaces equipped with semitransparent quartz process tubes. The model takes into account the thermal behavior of the thermocouples. It is shown that currently used temperature controllers are highly inefficient for very large scale integration applications. Based on the model an alternative temperature controller of the linear-quadratic-Gaussian type is proposed which features direct wafer temperature control. Some simulation results are given.
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 1913-1915 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The far infrared (FIR) photoconductivity of GaAs/AlGaAs multiquantum wells (MQWs) doped with silicon has been investigated. The spectral response is consistent with extrinsic photoconductivity from shallow donors with an effective Rydberg of approximately 10.5 meV. The time-resolved photoconductivity due to stimulation with a cavity-dump FIR laser is measured. Subnanosecond rise and decay times are implied for the MQWs investigated; these times are shorter than for the corresponding bulk cases. Possible effects of geometric confinement on recombination rates are discussed. For a 150-period MQW, the responsivity at 118 μm is approximately 105 V W−1 .
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 806-813 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Temperature profiles were calculated numerically for a three-layer stack of SiO2-Si-SiO2 on top of a monocrystalline Si substrate. The stack was locally heated by a CO2 laser whereas the wafer background temperature was controlled by a heat chuck. The calculation method makes it possible to simulate temperatures as functions of laser power, spot radius, scan speed, substrate bias temperature, and layer thickness. These parameters play a major role in CO2 laser recrystallization of polycrystalline silicon for making single crystalline silicon films on insulator films. It is shown that under conditions of maximum absorption experimental verification of the calculations is possible by measuring the recrystallized track width. A good agreement was found between the calculated and measured results.
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 1757-1765 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The instability of the electrical properties of semi-insulating GaAs materials has been investigated. The presence of chemical contaminants on the surface of the finished wafers is responsible. Simulated thermal conversion using intentional carbon-ion implantation indicates larger concentrations for the possible contaminants on the surface than that in the bulk. The contribution to instability due to preferential gettering of imperfections from bulk by the implant and annealing process was eliminated using intentional Ar-ion implantation. For the samples which exhibited a change in electrical conduction type, a linear relationship between the thickness of the type-converted surface layer and the square root of heat treatment time was observed. It is proposed that the causes for the instability are governed by conventional diffusion mechanisms with multiple electrically active species involved. A positive correlation was also observed between thermally induced electrical instability in ion-implanted material and a reduction in activation, peak carrier density, and Hall mobility.
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 5783-5791 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A theoretical model of fatigue in ferroelectric thin-film memories based upon impact ionization (e.g., Ti+4 to Ti+3 conversion in PbZr1−xTixO3), resulting in dendritic growth of oxygen-deficient filaments, is presented. The predictions of spontaneous polarization versus switching cycles Ps(N) are compared with both Monte Carlo simulations for a two-dimensional Ising model and with experimental data on small-grain (40 nm) sol-gel PZT films. Excellent agreement between theory and experiment is obtained. In addition to modeling the Ps(N) curves, the theory developed explains the observed linear proportionality between switching time ts(N) and polarization Ps(N) during fatigue; other models of aging do not account for this. Earlier theories of switching are also extended to include finite grain sizes, surface nucleation, triangular drive pulses, and dipolar forces. Good agreement with sol-gel PZT switching data is obtained.
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