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  • American Institute of Physics (AIP)
  • American Meteorological Society
  • 2015-2019  (7)
  • 1985-1989  (11)
  • 2018  (7)
  • 1987  (11)
  • 1
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 51 (1987), S. 1545-1547 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: HgTe-CdTe superlattices and other microstructures such as single and double barrier tunneling structures are commonly grown by molecular beam epitaxy with the mercury flux continuously on the sample during the growth. This means that some mercury will be incorporated in the CdTe layers. We present here, for the first time, a measurement of the amount of mercury incorporated in thin layers of CdTe. X-ray photoelectron spectroscopy was used to measure the amount of mercury. The amount of mercury was found to be between 3 and 9% for CdTe (111)B, depending on the growth conditions. The amount of mercury was found to increase with mercury flux and to decrease as the substrate temperature was increased. Under the same conditions, it was found that much more mercury was incorporated in the (100) orientation. The type of substrate (CdTe or GaAs) was not found to influence the results. These results indicate that the amount of mercury in the CdTe layers of HgTe-CdTe superlattices is not quite as low as expected from measurements of thick CdTe layers, but it can be low enough that it does not influence significantly the results on the superlattice system in the (111) orientation.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 120-125 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Single and multiple quantum wells with well widths ranging from 10 to 135 A(ring) were grown by atmospheric pressure organometallic chemical vapor deposition and characterized by photoluminescence (PL) and electrical measurements. Compared with single layers of high-purity GaAs and AlGaAs which have high intensity near band-edge excitonic transitions, the quantum well (QW) structures exhibit very strong luminescence of the discrete QW eigenstates. The intense QW signals indicate that the carrier confinement efficiency of the wells is very high, which is also supported by significant mobility enhancement in the samples. The sharp PL lines suggest high quality and smoothness of the well interfaces.
    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 62 (1987), S. 2466-2469 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: GaAs and AlGaAs/GaAs multiple quantum wells (MQW) were selectively deposited on GaAs substrates patterned with native oxide, and photoluminescence (PL) characteristics of both the single crystal grown in open windows and the polycrystalline material deposited on the oxide masks were studied. Well-resolved distinct quantum-well (QW) transition peaks indicate no degradation of the epitaxial material quality in the small single-crystal areas. The PL of polycrystalline GaAs is very weak and the peak is centered around the near-band-edge transition energy of GaAs. Polycrystalline MQW structures exhibit much stronger PL signals, and the peak position shifts corresponding to the widths of the QWs grown. These results suggest that the quantum size effect is preserved in the polycrystalline material.
    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 61 (1987), S. 2074-2077 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ultrasound velocity measurements may be used to study the dynamics of the spin-glass phase. Near the transition temperature, the sound speed deviates slightly from that of the pure nonmagnetic host. We measured the velocity anomaly in a 1-at. % CuMn sample near the transition temperature (12 K) as a function of frequency from 5 to 100 MHz and found its size to be frequency independent. We also found changes in the anomaly when the sample was field cooled in transverse 4.7- and 14.2- kG fields. These results are discussed in light of previously published theoretical predictions.
    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 62 (1987), S. 1729-1733 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The damage induced by CHF3+C2F6 plasma etching on GaAs(100) was studied. We exposed GaAs(100) surfaces to various etching conditions and monitored sheet resistance, carrier concentration, and Hall mobility. Significant losses of Hall mobility and carrier concentration, and an increase in sheet resistance were observed only when CHF3 was introduced into the plasma. After annealing at 400 °C for 55 min, sheet resistance was restored nearly to the value obtained before the plasma exposure. We believe that the damage was produced by hydrogen atoms or ions dissociated from CHF3 in the plasma. In contrast to the general belief that plasma etching induces the least damage among dry etching techniques [such as reactive ion etching (RIE) and reactive ion beam etching (RIBE)], our plasma etching damage was comparable to previously reported RIE or RIBE damage.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 30 (1987), S. 1221-1224 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The fully relaxed magnetohydrodynamic (MHD) equilibrium is obtained by imposing nonideal MHD perturbations constrained by the total plasma current. The minimum energy state governed by Δ*ψ+CF exp(ψ/λ)+CpR2 exp(5ψ/4λ) =0 reveals properties of profile consistency, bifurcated solutions, and a loss of equilibrium condition. It predicts the transport coefficient peaked at the plasma edge and a unique current profile for given q0 and ql.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 30 (1987), S. 3204-3211 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The Hamiltonian four-field model is a simplified description of nonlinear tokamak dynamics that allows for finite ion Larmor radius physics, as well as other effects related to compressibility and electron adiabaticity. Much simpler than some previous descriptions of the same physics, it still preserves essential features of the underlying exact dynamics. In particular, because it is a Hamiltonian dynamical system it conserves the appropriate Casimir invariants, as well as avoiding implicit, unphysical dissipation. Here the model is derived and interpreted, its Hamiltonian nature is demonstrated, and its constants of motion are extracted.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 54-59 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We continue our study of the optical dephasing of impurities by phonons. The pure dephasing contribution to the homogeneous linewidth is calculated to all orders in the excitation–phonon interaction. We introduce a microscopic model for the pseudolocal phonon spectral density when the impurity is in the ground electronic state. This microscopic model improves upon our previous phenomenological model. The model is applied to several experimental systems—in all cases, the theoretical results provide a reasonably accurate description of the temperature-dependent linewidth with no adjustable parameters.
    Type of Medium: Electronic Resource
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  • 9
    Publication Date: 2018-07-23
    Description: A lightweight and low-cost unmanned aerial vehicle (UAV) system for coastal wave and tide measurements is developed. This system is based on an assembly of a multirotor UAV, a robotic lidar, an altitude and heading reference system (AHRS), and a real-time kinematic (RTK) Global Navigation Satellite System (GNSS). A great advantage of the system is that it can be operated at low altitude in a few meters; the accuracy and spatial resolution can therefore be increased. When the system was moved up and down in 2–12 m, the root-mean-square error (RMSE) was approximately 5 cm compared to the ground truth value measured by a manual RTK GNSS. The system was operated in a hover mode to measure the tide and waves in the field. The results of using the UAV–RTK lidar system were consistent with those of in situ measurements using a pressure sensor. The root-mean-square errors between the two techniques for measurements of tidal elevation, significant wave height, and wave period were 4.9 cm, 4.8 cm, and 0.028 s, respectively. This finding suggests the system could be applied to measure instantaneous sea surface displacement. The system provides the potential for using a low-cost, extremely portable, and efficient tool for monitoring wave properties, topographic changes, and water-level gradients in coastal zones.
    Print ISSN: 0739-0572
    Electronic ISSN: 1520-0426
    Topics: Geography , Geosciences , Physics
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  • 10
    Publication Date: 2018-03-20
    Description: This study reports the different effects of tropical and subtropical sea surface temperature anomalies (SSTAs) on the mean tropical cyclone (TC) genesis location in the western North Pacific (WNP), a TC–SSTA relationship that has been largely ignored. In the Pacific, the interannual variability of the tropical SSTA in the boreal summer is characterized by an El Niño–Southern Oscillation (ENSO)-like pattern, whereas the subtropical SSTA exhibits a Pacific meridional mode (PMM)-like structure. Partial correlation analysis reveals that the ENSO-like and PMM-like SSTAs dominate the south–north and east–west shift of mean TC genesis location, respectively. The 2015/16 El Niño was a strong event comparable with the 1997/98 event in terms of Niño-3.4 SSTA. However, the mean TC genesis location in the WNP during the summer of 2015 exhibited an unprecedented eastward shift by approximately 10 longitudinal degrees relative to that in 1997. Whereas the ENSO-like SSTAs in 1997 and 2015 were approximately equal, the amplitude of the PMM-like SSTA in 2015 was approximately twice as large as that in 1997. Numerical experiments forced by the ENSO-like and PMM-like SSTAs in June–August 2015 reveal that the positive PMM-like SSTA forces an east–west overturning circulation anomaly in the subtropical North Pacific with anomalously ascending (descending) motion in the subtropical central (western) Pacific. The mean TC genesis location in the WNP therefore shifts eastward when warmer SST occurs in the subtropical eastern Pacific. This finding supports the hypothesis that the extremely positive PMM-like SSTA in the summer of 2015 caused the unprecedented eastward shift of the TC genesis location in the WNP.
    Print ISSN: 0894-8755
    Electronic ISSN: 1520-0442
    Topics: Geography , Geosciences , Physics
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