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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 29 (1988), S. 305-307 
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: Nonstationary solutions of linear Fokker–Planck equations with arbitrary drift and diffusion coefficients are derived. Using Lie algebraic techniques the time-evolution operator is given as a product of exponentials of the differential operators appearing in the equations.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 82 (1985), S. 5295-5296 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The fluorescence spectrum of NeBr2 was recorded using a dye laser as the excitation source. The rhodamine 6G dye was pumped with an Ar2 laser to obtain a bandwidth of 0.001 cm−1 tunable over 1 cm−1 segments. The 1 cm−1 segment was divided into 1024 data points and was recorded in 9 min sequences. The spectra are shown in Fig. 1. (AIP).
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 58 (1987), S. 1477-1486 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The detailed description, the experimental demonstration, and the design of single-mode microwave cavity applicators are presented. These microwave applicators utilize an internally tuned, single-mode (or selective multimode) cylindrical cavity to focus and match microwave energy into cylindrical rod, disk-, or slab-shaped material loads. The combination of mode focus control and variable, internal cavity matching allows the efficient coupling of microwave energy into a wide range of solid material loads. The experimental operation of these applicators is demonstrated for low loss to lossy materials, which include nylon, water, and semiconducting silicon wafers. Overall microwave coupling efficiencies of 70%–95% were measured and experiments demonstrated the ability to precisely control material heating. The single-mode fields can be used to heat and diagnose during processing, and on-line process diagnosis was experimentally demonstrated using cavity perturbation theory. When using these cavity applicators, many system variables such as tuning control, cavity electric field strength, input, and reflected power are available as potential process system feedback signals for automated intelligent processing. These applicators can be used to carefully study the fundamentals of electromagnetic interactions of many materials. Applications include the electromagnetic heating of foods, semiconducting and biological materials, and the heating and curing of epoxy and composite materials.
    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 64 (1988), S. 3380-3392 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Experiments have characterized the operation of a LaB6 triode gun in a standard three-lens column of the type used for Gaussian electron-beam lithography and scanning electron microscopy. A series of images representing cross sections of the three-dimensional spatial distribution of current emitted from the gun is obtained by configuring the electron optics as a scanning confocal microscope. The gun acts as an immersion objective whose image is scanned by deflection coils and focused by the condenser lenses onto a pinhole transmission detector. Characteristics of the emission distribution include an emission image of the cathode surface situated between two distinct beam crossovers whose origin is either the apex (001) and {310} planes or the large {110} planes on the machined 90° cone angle of the cathode surface. Virtual objects are imaged when the back focal plane of the condensers falls inside the high-field region of the gun. The target axial brightness is dependent on gun excitation and angular acceptance angle. The temperature-dependent brightness of the cathode is used to determine its effective emission area, work function, and surface electric field. Beam positional stability of three-carbon-mounted LaB6 directly heated cathodes is measured. However, for measurement times ≤100 h the drift rate is found to be limited by thermal expansion of the movable anode assembly and not the particular cathode mounting technique.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 3530-3536 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Heat capacity of a pure rubidium cyanide crystal has been measured between 14 and 330 K with an adiabatic calorimeter. A first order phase transition was found at (132.30±0.05) K in agreement with the previous dielectric study. The transition enthalpy and entropy are 1280 J mol−1 and 10.2 J K−1 mol−1, respectively, of which (742±2) J mol−1 and (5.65±0.02) J K−1 mol−1 are the discontinuous parts. Under the assumption that the orientational disorder of the cyanide ion in the cubic phase is eightfold, a residual entropy of 5.43 J K−1 mol−1 was derived from the transition entropy and related to the head-to-tail disorder of the anions. The disorder causes a glass transition at 30 K. The enthalpy relaxation time determined by spectroscopic use of the adiabatic calorimeter agrees very well with the dielectric relaxation time extrapolated to the lower temperature, giving evidence for the frozen disordered state to be a dipolar glass.
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  • 6
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 2227-2229 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Simultaneous measurement of both the conduction- and valence-band dispersion curves in single strained-layer structures is presented. These measurements rely on the application of recent observations regarding breaking of the usual selection rules for interband magnetoluminescence transitions in modulation-doped structures. Low-temperature magneto-luminescence data for three representative InGaAs/GaAs n-type single-strained quantum well structures are presented. For energies approaching 50 meV above the band gap, we find that the conduction band is parabolic with an effective mass of 0.071m0. Over the same energy range, the valence bands are highly nonparabolic.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 1877-1878 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Conduction-band and valence-band energies are presented for ternary III-V compounds in a novel way. These data are used to evaluate new material combinations for heterostructure devices.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 1324-1326 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report low-field electroreflectance (ER) spectra of an all-semiconductor multilayer optical mirror structure. The structure, consisting of alternating blocks of AlAs/Al0.5Ga0.5 As and Al0.5Ga0.5As/GaAs multiple quantum well layers, was grown by molecular beam epitaxy without wafer rotation. Thickness variations across the wafer produce a position-dependent reflectance spectrum. The observed line shape of the band-edge exciton depends on its wavelength position relative to the mirror spectrum and cannot be explained by ordinary ER theory, due to the rapidly varying background mirror reflectance. Computer simulations, using the matrix method to calculate the reflectance for different layer thicknesses and exciton energies, agree qualitatively with the data. A strong enhancement in ER response is predicted near the minima in the mirror spectrum. This enhancement is important in electo-optic reflectance modulators.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 1098-1100 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report electrical transport and optical studies of the efficiency with which an In0.2Ga0.8As/GaAs strained-layer superlattice (SLS) can filter threading dislocations generated in a thick In0.1 Ga0.9 As layer grown on GaAs. The electrical studies, the first of their kind, rely on a novel test structure which allows electrical characterization of just the top portion of the SLS, with the bottom portion acting as the dislocation filter. For optical characterization we detect dislocations directly by photoluminescence microscopy. The electrical results show that ∼3–6 periods of filtering are needed to attain high mobilities. The photoluminescence microimages show a small density of dislocations near the top of an eight-period SLS but no dislocations for 11 or more periods. Filtering with In0.2Ga0.8As/GaAs SLS's is more effective than with GaAs0.8P0.2/GaAs SLS's, possibly because of larger interlayer differences in strain and elastic constants for the former.
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 2819-2827 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thirty-seven of 97 AlxGa1−xAs laser diodes from three tests conducted in vacuum (10−6 Torr) at a −20 °C heat sink temperature (Tj∼0 °C) failed catastrophically. Causes of failure varied from testing error to defects in the metallization. In all cases, p-side anomalies allowed indium solder (and probably gold in addition to indium in one case) to migrate into the GaAs bulk, causing the observed failures. The results of this research show that the integrity of the p-side metallization is crucial for reliable operation. Stringent controls have been implemented in the design and processing of the p-side metallization and catastrophic failures due to p-side anomalies have not been observed in subsequent life tests. A correlation was made between shifts in the forward voltage at 1 mA (Vf at 1 mA) and the specific failure mechanisms found in this research. In all cases Vf at 1 mA was found to decrease. The amount of decrease depended on the failure mechanism. A quantitative model is presented that explains the shift in Vf as a function of the type of defect in the active region.
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