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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 6165-6169 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin film reactions of Cu/Al multilayer films were investigated by differential scanning calorimetry and transmission electron microscopy. Sequential intermetallic compound formation was found in the temperature range from 300 to 620 K. With excess copper present in the as-deposited trilayer and multilayer films, the observed sequence was CuAl2 and Cu9Al4, and the interfacial reactions were controlled by interfacial and grain boundary diffusion. The activation energies for the formation of CuAl2 and Cu9Al4 are 0.78±0.11 and 0.83±0.2 eV, respectively.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We used microwave self-resonant and magnetically modulated microwave absorption techniques to measure the London penetration depth, λ, and coherence length, ξ, in the direction parallel and perpendicular to the a–b plane of YBCO films. We found that both λ and ξ were anisotropic; it appeared that the value of λ(parallel)(0) was about 1800 A(ring) and λ⊥(86.5) about 26 000 A(ring), where λ(parallel) is the penetration depth for the applied microwave electric field parallel and λ⊥ perpendicular to the film plane (c-axis is perpendicular to the film plane). We deduced ξ(parallel) to be equal to 129 A(ring) and ξ⊥ 40 A(ring) at 86.5 K. The anisotropy factor γ we determined to be about 3.
    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 69 (1991), S. 6701-6703 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Persistent photoconductivity (PPC) mechanisms, as well as the similarities and the differences of PPC properties in II-VI and III-V semiconductor alloys have been investigated. The potential applications based on PPC phenomenon in these two kinds of materials are discussed. We have observed that PPC induced in a II-VI mixed crystal by visible (above band gap) illumination can be quenched by long wavelength infrared radiation even at room temperature, which further supports our interpretation that PPC in II-VI mixed crystals is caused by random local potential fluctuations induced by compositional fluctuations. A newly developed infrared detector based on the PPC infrared quenching property of II-VI semiconductor alloys is also reported.
    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 79 (1996), S. 7001-7004 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The dynamic processes of the free excitonic transitions in GaN grown by metal-organic chemical-vapor deposition (MOCVD) have been studied. The recombination lifetimes of the A and B excitons have been measured at different temperatures and excitation intensities, from which radiative recombination lifetimes of about 0.35 and 0.3 ns for the A and B excitons, respectively, have been obtained. An increase in excitation power has resulted in a drastic enhancement in the radiative decay rate as well as in the exciton photoluminescence quantum yield, suggesting the excitonic transitions may provide gain for laser actions in GaN. The high quality as well as high purity of the investigated MOCVD sample has been demonstrated by the observations of (1) the free A- and B-excitonic transitions, (2) excited states of the free excitons, (3) narrow free excitonic emission linewidths (1.7 meV at 10 K), (4) low electron concentration, and (5) high electron mobilities (∼600 cm2/V s). © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Continuous-wave and time-resolved photoluminescence spectroscopies have been employed to study the band-edge transitions in GaN epitaxial layers grown by plasma assisted molecular beam epitaxy. In addition to the neutral-donor-bound exciton transition (the I2 line), a transition line at about 83 meV below the band gap has been observed in an epitaxial layer grown under a lower plasma power or growth rate. This emission line has been assigned to the band-to-impurity transition resulting from the recombination between electrons bound to shallow donors and free holes D0, h+). Systematic studies of these optical transitions have been carried out under different temperatures and excitation intensities. The temperature variation of the spectral peak position of the D0, h+) emission line differs from the band gap variation with temperature, but is consistent with an existing theory for D0, h+) transitions. The dynamic processes of the D0, h+) transition have also been investigated and subnanosecond recombination lifetimes have been observed. The emission energy and the temperature dependencies of the recombination lifetime have been measured. These results have provided solid evidence for the assignment of the D0, h+) transition and show that the motions of the free holes which participated in this transition are more or less restricted in the plane of the epitaxial layer at temperatures below 140 K and that the thermal quenching of the emission intensity of this transition is due to the dissociation of neutral donors. Our results show that time-resolved photoluminescence spectroscopy can be of immense value in understanding the optical recombination dynamics in GaN. © 1996 American Institute of Physics.
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 3110-3114 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electrical properties of Al–p+-GexSi1−x contacts were studied using transmission line measurements. For this study the GeSi alloy layers were selectively formed with 30 or 90 keV Ge implantation into Si, a technique which offers a simple, self-aligned process for the fabrication of such layers. Measurements of the current–voltage characteristics showed that the metal–alloy contacts were ohmic over the voltage range examined. The specific contact resistivity was found to be a function of Ge concentration, decreasing with increasing Ge concentration for concentrations below a critical value and increasing with increasing Ge concentration above this value. The initial decrease in specific contact resistivity is attributed to the effect of Ge on the contact barrier height and width, an effect which is caused by the reduction in the band gap of the alloy. The subsequent increase in specific contact resistivity at higher Ge concentrations is believed to be due to the presence of a high concentration of dislocations in the alloy layer. The thermal stability of contacts is also reported. © 1996 American Institute of Physics.
    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 78 (1995), S. 3299-3302 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Fe–N films were prepared by ion-beam-assisted deposition at different N/Fe atomic arrival ratios to the substrates. Films consisted of nitrogen-rich α-Fe and different phases of iron nitrides including ζ-Fe2N, ε-Fe2-3N, and γ′-Fe4N were formed. The phase composition of Fe–N films was found to depend sensitively on the N/Fe atomic arrival ratio and deposition temperature. The magnetic properties of the films mainly depends on phase composition. It was found that nitrogen-rich α-Fe films exhibited higher Ms than that of the pure iron film, and their Ms could be increased further by vacuum annealing at relatively low temperatures. © 1995 American Institute of Physics.
    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 75 (1994), S. 5734-5736 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Relaxation of thermoremanent magnetization (TRM) of Cd1−xMnxTe diluted magnetic semiconductors (DMS) in the spin-glass state have been studied under light illumination. The relaxation of TRM can be described well by a power law decay, M(t)=M(t0)t−α (t(approximately-greater-than)t0, t0∼2 s). The variations of the decay parameter α with the illumination light intensity has been measured and a relation which indicates that α is proportional to the photogenerated carrier concentration n has been observed.
    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 81 (1997), S. 1807-1812 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this article, we use Monte Carlo methods to study the interaction of high power laser pulses with electrons in the conduction band of semiconductors. The laser field is represented by a sinusoidal electric field which tends to cause an oscillatory motion in the electrons. The scattering of electrons from the lattice force the electrons to lose phase coherence with the field. The approach is applied to silicon. We use the approach to examine the carrier energy distribution and material breakdown due to the transfer of energy from the laser to the electrons followed by impact ionization. The impact ionization coefficient, α, and its dependence on the laser frequency and field strength is examined and compared to the values in a dc field. In general, the ac value is smaller than the dc value, but at low frequencies and high field strengths, the ac impact ionization coefficient approaches the dc value at the same rms field value. The importance of collisions in the energy transfer process is elucidated. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 1808-1810 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electrical properties of Mg-doped p-type GaN grown by metalorganic chemical vapor deposition have been investigated by Hall effect and conductivity measurements. Metastability and persistent photoconductivity effects have been observed in GaN. It was found that at low temperatures, it takes several hours for the free hole concentration to reach its equilibrium value in the dark as well as in the photoexcited state, implying a bistable nature of impurities in p-type GaN. Temperature dependence of these behaviors have been studied, from which the energy barrier for free hole capture by ionized impurities as well as between the metastable and the stable states of neutral impurities have been obtained. © 1996 American Institute of Physics.
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