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  • 1
    Electronic Resource
    Electronic Resource
    Optical spectroscopy at cryogenic temperatures using a Block–Piermarini diamond-anvil cell (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 772-775 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A simple experimental setup allowing low-temperature high-pressure spectroscopy, with in situ pressure adjustment, is described. A Block–Piermarini diamond-anvil cell is used together with standard laboratory materials. Results of semiconductor photoluminescence studies, using argon as a pressure-transmitting medium, are given as an illustration and are also used for the study of the pressure conditions. Pressure homogeneity is better than 100 MPa up to 6 GPa, and the residual uniaxial component of the stress can be lower than 100 MPa.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1139826
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  • 2
    Electronic Resource
    Electronic Resource
    Two-phase high-performance Nd–Fe–B powders prepared by mechanical milling (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 1540-1544 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Nanocrystalline two-phase NdFeB+α-Fe material was prepared by milling techniques and subsequent heat treatment. These isotropic exchange-coupled powders show excellent hard magnetic properties with enhanced remanences up to 1.20 T and energy densities (BH)max around 150 kJ/m3. The performance is based on (i) the use of grain refining additions, (ii) partial substitution of Fe by Co and (iii) the use of pre-melted master alloys. The distribution of Co among the hard and soft magnetic phases upon milling and annealing is studied via Curie temperature measurements up to 10 at. % Co substitution. The effect of Co on the intrinsic properties is estimated and clarifies the extrinsic magnetic behavior. An overview of samples prepared with different milling techniques and compositions is presented. It summarizes the above listed, three different approaches to improve the magnetic performance together with the influence of the phase ratio of hard and soft magnetic phases. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1380223
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  • 3
    Electronic Resource
    Electronic Resource
    Smooth, pseudosmooth, and rough GaAs/AlxGa1−xAs interfaces: Effect of substrate misorientation (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 2605-2607 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: GaAs/AlxGa1−xAs quantum well and superlattice structures have been grown at 600 °C by molecular beam epitaxy on GaAs (001) substrates exactly oriented or slightly misoriented towards (111) Ga and (111) As. It is shown that for the growth conditions used, the step orientation (nature) has a striking influence on the photoluminescence (PL) features of the grown structures: steps along [1¯10] (Ga-type steps) lead to sharp PL lines (pseudosmooth interfaces), while a considerable broadening of the PL (rough interfaces) is obtained when the steps are along [110] (As-type steps).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101967
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  • 4
    Electronic Resource
    Electronic Resource
    Photoluminescence and Raman studies of residual stresses in GaAs directly grown on InP (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 1558-1560 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report first-order Raman spectroscopy and low-temperature photoluminescence (PL) studies of GaAs layers grown by metalorganic vapor phase epitaxy (MOVPE) on InP (100) substrates. From both the shift of the longitudinal-optical phonons in the Raman spectra and the splitting and shift of band-edge exciton lines in PL, the epilayers are found to be under (100) coplanar tensile stress, which is consistent with the difference between the thermoelastic properties of the two materials. The PL analysis shows that carbon is the main residual acceptor impurity in MOVPE-grown GaAs/InP.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102243
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  • 5
    Electronic Resource
    Electronic Resource
    Relaxation dynamics of multilevel tunneling systems (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 1749-1756 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A quantum mechanical treatment of an asymmetric double-well potential (DWP) interacting with a heat bath is presented for circumstances where the contribution of higher vibrational levels to the relaxation dynamics cannot be excluded from consideration. The deep quantum limit characterized by a discrete energy spectrum near the barrier top is considered. The investigation is motivated by simulations on a computer glass which show that the considered parameter regime is "typical" for DWPs responsible for the relaxation peak of sound absorption in glasses. Relaxation dynamics resembling the spatial- and energy-diffusion-controlled limit of the classical Kramers' problem, and Arrhenius-type behavior is found under specific conditions. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.473313
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  • 6
    Electronic Resource
    Electronic Resource
    Structural and optical characterization of ZnSe single crystals grown by solid-phase recrystallization (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 2983-2989 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We investigate by high-resolution x-ray diffraction (HRXRD), temperature-dependent photoluminescence (PL) and reflectivity spectroscopies, and low-temperature selective-photoluminescence spectroscopy ZnSe single crystals grown by solid-phase recrystallization. HRXRD reveals the high structural perfection of the samples which exhibit rocking-curve linewidths in the 15–20 arcsec range. The low-temperature PL spectra are dominated by the so-called Ideep1 excitonic line, a neutral-acceptor bound-exciton line I1, the free-exciton emission FX, and the n=2 excited state of FX. We identify the main residual impurities to be Li acceptors. Donor–acceptor pair bands are very hardly detected at low temperature which indicates a low donor content. A major characteristics of these samples is the quasi-absence of any Cu-related deep emission which generally plagues the PL spectra of bulk ZnSe. Consequently, Ideep1 is ascribed to Zn-vacancy–donor complexes. Finally, from the temperature dependence of the PL emission and reflectivity, the band-gap energy of bulk ZnSe is found to linearly shrink with the temperature above 80 K at a rate of −4.3×10−4 eV K−1. The room-temperature gap is estimated to 2720±2 meV. Our results indicate that solid-phase recrystallization produces ZnSe samples with the highest structural quality and purity achievable at present time. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363155
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  • 7
    Electronic Resource
    Electronic Resource
    Chlorine-related neutral complex in screen-printed CdTe (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3386-3389 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Detailed low-temperature optical characterization of screen-printed CdTe is presented. Photoluminescence and excitation spectroscopy demonstrate the existence of a new defect center systematically found in all the deposited layers. A possible explanation is based on a local mode induced by the defect but the experimental data are also very similar to those presented by Monemar et al. [Phys. Rev. B 25, 7719 (1982)] for two complexes in GaP:Cu. including the characteristic orange luminescence (COL) center, and for an Ag-related complex in ZnTe:Ag. The growth process as well as the optical results lead to an identification of the defect with an isoelectronic complex involving Cl ([VCd 2ClTe]).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346342
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  • 8
    Electronic Resource
    Electronic Resource
    Kinetic description of cyclotron-range oscillations of a non-neutral plasma column (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 5 (1998), S. 873-882 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The kinetic analysis introduced by Prasad, Morales, and Fried [Prasad et al., Phys. Fluids 30, 3093 (1987)] is used to derive damping conditions and a differential equation for azimuthally propagating waves in a non-neutral plasma column in the limits rl/L(very-much-less-than)1 and krl(very-much-less-than)1 (where rl is the Larmor radius, k is the wave number, and L is the density scale length). The predictions of the kinetic analysis are verified using a two-dimensional particle-in-cell simulation of Bernstein modes in a thermal rigid-rotor equilibrium. Differences between modes in a strongly magnetized limit and near the Brillouin limit are studied in the simulation. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872654
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  • 9
    Electronic Resource
    Electronic Resource
    Propagation of nonlinear pulses in a non-neutral plasma slab (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 3033-3043 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The axial propagation of linear and nonlinear pulses in a strongly magnetized non-neutral plasma slab is studied using a recently developed particle simulation code [Ramachandran et al. Phys. Fluids B 5, 2733 (1993)]. These pulses are generated by suddenly applying a negative potential to wall antennas on the confining walls. Theoretical predictions are compared to electrostatic particle simulations over a wide range of excitation amplitudes, and are shown to be in excellent agreement. A simple theoretical model is developed to describe the formation of the observed electron bursts and the associated wave breaking that arises for very large antenna potentials. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871200
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  • 10
    Electronic Resource
    Electronic Resource
    A sublimation probe for the injection of high-Z impurities into fusion devices (1999)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 63-67 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: For the investigation of high-Z impurities in the ASDEX Upgrade tokamak a sublimation probe was developed and tested. With this probe it is possible to inject materials, that sublimate at temperatures from about 50 to 150 °C into the plasma through a controllable valve. For the investigation of the tungsten transport in ASDEX Upgrade the probe was operated with tungsten carbonyl. The flux of tungsten, which is difficult to determine directly because of the uncertain atomic data, can be determined using the fluxes of oxygen and carbon, the atomic data of which are better known. In this article the setup of the probe and first experiments are described. Here the layer of deposited tungsten was investigated and the number of emitted photons per ionization (the S/XB ratio) for the 400.8 nm line of W I was estimated. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149575
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