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  • 1
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    Structural and electronic properties of GaN nanowires with embedded InxGa1−xN nanodisks (2015)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2015-07-16
    Description: In the present study, the effects of various types of strain and indium concentration on the total energy and optoelectronic properties of GaN nanowires (NWs) with embedded In x Ga 1− x N nanodisks (NDs) are examined. In particular, the bi-axial, hydrostatic, and uniaxial strain states of the embedded In x Ga 1− x N NDs are investigated for multiple In concentrations. Density functional theory is employed to calculate the band structure of the NWs. The theoretical analysis finds that the supercell-size-dependent characteristics calculated for our 972-atom NW models are very close to the infinite supercell-size limit. It is established that the embedded In x Ga 1− x N NDs do not induce deep states in the band gap of the NWs. A bowing parameter of 1.82 eV is derived from our analysis in the quadratic Vegard's formula for the band gaps at the various In concentrations of the investigated In x Ga 1− x N NDs in GaN NW structures. It is concluded that up to ∼10% of In, the hydrostatic strain state is competitive with the bi-axial due to the radial absorption of the strain on the surfaces. Above this value, the dominant strain state is the bi-axial one. Thus, hydrostatic and bi-axial strain components coexist in the embedded NDs, and they are of different physical origin. The bi-axial strain comes from growth on lattice mismatched substrates, while the hydrostatic strain originates from the lateral relaxation of the surfaces.
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 2
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    Defects, strain relaxation, and compositional grading in high indium content InGaN epilayers grown by molecular beam epitaxy (2015)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2015-10-17
    Description: We investigate the structural properties of a series of high alloy content InGaN epilayers grown by plasma-assisted molecular beam epitaxy, employing the deposition temperature as variable under invariant element fluxes. Using transmission electron microscopy methods, distinct strain relaxation modes were observed, depending on the indium content attained through temperature adjustment. At lower indium contents, strain relaxation by V-pit formation dominated, with concurrent formation of an indium-rich interfacial zone. With increasing indium content, this mechanism was gradually substituted by the introduction of a self-formed strained interfacial InGaN layer of lower indium content, as well as multiple intrinsic basal stacking faults and threading dislocations in the rest of the film. We show that this interfacial layer is not chemically abrupt and that major plastic strain relaxation through defect introduction commences upon reaching a critical indium concentration as a result of compositional pulling. Upon further increase of the indium content, this relaxation mode was again gradually succeeded by the increase in the density of misfit dislocations at the InGaN/GaN interface, leading eventually to the suppression of the strained InGaN layer and basal stacking faults.
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 3
    Electronic Resource
    Electronic Resource
    Rotationally resolved spectra of the 610 and 610110 band of benzene in a moderately cold molecular beam: Spectral and dynamical analysis (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 4555-4563 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Rotationally resolved spectra of the 610 and 610110 band of benzene, C6H6, in a supersonic molecular beam at rotational temperatures between 8 and 50 K are reported. The spectra consist of lines of 85 MHz linewidth. An unexpectedly low saturation intensity of ≈104 W/cm2 is found for the observed one-photon transitions, and it is shown that the saturation intensity differs for different rotational lines within one vibronic band. The rovibronic line spectra are analyzed within the framework of a rigid symmetric top model and highly precise values of the rotational constants are determined. In addition, the rotationless transition frequencies ν00 are obtained with high precision. The spectrum of the 610 band shows no signs of rotational perturbations, while the 610110 band at higher vibrational excess energy shows indications of perturbations for lines with K' above 10. The decay times of single rotational states within the 6111 vibronic state are reported and no rotational dependence of the decay time is found in agreement with the statistical limit character of the interstate nonradiative process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456743
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  • 4
    Electronic Resource
    Electronic Resource
    Passivation of an anodic oxide/p-Si interface stimulated by electron injection (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 4636-4642 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The positive oxide charge (Qox) and the concentration of nonradiative recombination defects (Nit) at a thin anodic oxide/p-Si interface are probed in situ by pulsed photovoltage and photoluminescence techniques during electron injection. Qox and Nit decreased strongly due to electron injection. The observed effect is suggested to be inverse to the negative-bias-temperature instability. Defect reactions at the anodic oxide/p-Si interface are discussed. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1356431
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  • 5
    Electronic Resource
    Electronic Resource
    Growth mechanisms of CdTe during molecular beam epitaxy (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 3492-3496 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report here on studies of the growth mechanism of CdTe during molecular beam epitaxy on (100) oriented CdTe substrates by reflection high energy electron diffraction (RHEED). The growth rate of CdTe as a function of the Cd/Te ratio in the impinging molecular beam was investigated in detail. The growth rates were determined by RHEED intensity oscillations. Fluxes were calibrated by film thickness measurements. From the growth rates dependence on the Cd/Te flux ratio we determined the Cd and Te sticking coefficients by comparing the results with kinetic models of molecular beam epitaxial growth. Both Cd and Te sticking coefficients are dependent on the surface concentration of free Cd and Te sites, respectively. The main result is that the influence of a precursor state has to be taken into account to describe the experimental results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351426
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  • 6
    Electronic Resource
    Electronic Resource
    Domain structure and anisotropy of exchange coupled Co/Cr/Fe multilayers (abstract) : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 4531-4531 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied the magnetic properties of Co/Cr/Fe multilayers by means of magneto-optic methods. These multilayers are of special interest because they combine different anisotropies and exchange coupling through the nonmagnetic Cr-spacer layer which was found to oscillate from ferromagnetic to antiferromagnetic coupling. The samples were grown by MBE methods on MgO(100) substrates at temperatures of about 300 °C. The fourfold crystalline symmetry is also obtained in the magnetic easy axis structure of Fe and Co. From the results of magneto-optic Kerr hysteresis loops we were able to distinguish between crystalline anisotropy and exchange coupling contributions. Additional monitoring of the domain structure by applying longitudinal Kerr microscopy was necessary to identify the regime were magnetization reversal occurs via domain wall motion or coherent rotation of the magnetization of the entire layer, respectively. From these results we were able to perform numerical simulations of the micromagnetic properties of trilayer samples. We discuss the results in terms of bilinear and biquadratic coupling. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361713
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  • 7
    Electronic Resource
    Electronic Resource
    Hole-trapping sites and the mechanism of the photostimulated luminescence of the x-ray storage phosphor RbI:Tl+ (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 2430-2435 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Radiation damage centers generated by x irradiation at 80 and 300 K in the storage phosphor RbI:Tl+ were investigated with optically detected magnetic resonance and optical measurements. It is shown that the intensity of the photostimulated luminescence depends on the concentration of Tl2+ centers. Bleaching into any of the seven identified Tl2+ absorption bands destroys the Tl2+ centers and leads to a Tl+ emission as well as to VK centers. Proportionally to photodestruction of Tl2+ centers, the photostimulated luminescence is decreased. The traps for information storage in RbI:Tl+ are F centers and Tl2+ centers. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363078
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  • 8
    Electronic Resource
    Electronic Resource
    Structural and magnetic studies of FexCo1−x(001) alloy films on MgO(001) substrates (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 1055-1060 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin epitaxial FexCo1−x alloy films sputtered on MgO(001) substrates were studied by x-ray scattering and by the magneto-optical Kerr effect in order to investigate the structural phase stability induced by the substrate and to relate the magnetic properties to the alloy film structure. Alloy films with a thickness of about 20 nm and concentrations from x=1 to x=0.3 exhibit a bcc (001) growth with the in-plane [100] axis parallel to the MgO[110] axis. For pure Co (x=0) a fcc (001) structure with the Co[100] axis parallel to the MgO[100] axis was obtained. For x=0.15 no out-of-plane or in-plane Bragg peak could be observed, possibly due to the bcc-fcc structural phase transition. Kerr rotation angles in saturation as a function of x reveal a shape similar to the Slater–Pauling curve. Magnetic hysteresis measurements reveal a fourfold anisotropy with easy axes parallel to the FexCo1−x[100] crystal axis for 1≥x≥0.8, and parallel to the FexCo1−x[110] crystal axis for 0.7≥x≥0.3. In pure Co the easy axis lies parallel to the fcc-Co[110] crystal axis. Finally, for x=0.28 a step in the magnetic hysteresis in the FexCo1−x[11¯0] direction indicates an overlap of a fourfold and twofold magnetic anisotropy. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358965
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  • 9
    Electronic Resource
    Electronic Resource
    Optimization of modulation-doped Ga1−xInxAs/InP heterostructures towards extremely high mobilities (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 4489-4493 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This paper presents a study of the electrical and structural properties of inverted modulation-doped GaInAs/InP heterostructures grown by low-pressure metalorganic vapor phase epitaxy. First, the thickness of the GaInAs layer was optimized in lattice-matched samples to find the smallest thickness in which high Hall mobility is observed. Next, in a section closest to the InP the In content was varied. A steady increase of mobility with indium composition was observed. A maximum of 450 000 and 15 500 cm2/V s was obtained for a 10-nm-thick Ga1−xInxAs layer with x=0.77 at 6 and 300 K, respectively. Channels with higher indium content exceed the critical thickness and mobility drops off sharply. The decreasing mobility correlates with the formation of misfit dislocations at the interface indicating increasing scattering processes of the GaInAs layer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352789
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  • 10
    Electronic Resource
    Electronic Resource
    Two-temperature relaxation in nonideal partially ionized plasmas (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 1241-1249 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Evolution equations for the coupled relaxation of densities and temperatures for the components in nonideal partially ionized plasmas are given. In these equations many-body effects, such as screening, self-energy, and lowering of the binding energy, are included. The coupled equations are solved numerically for a hydrogen plasma consisting of electrons, protons, and atoms. Impact ionization, three-body recombination, and elastic processes are taken into account. Thermal relaxation times are determined and the results are compared with those from the literature. The influence of many-body effects on the evolution process are discussed. In some cases, a significantly increased lifetime of the two-temperature regime is found. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871748
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