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1

Digitale Medien

Raman characterization of single defect layers embedded in finite superlattices (1991)

Schwartz, G. P. ; Gualtieri, G. J. ; Sunder, W. A.

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 58 (1991), S. 971-973

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ISSN: 1077-3118

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Single defect layers embedded in finite, nominally periodic superlattices have been examined using Raman scattering. The spectrum of zone-folded acoustic phonons exhibits defect-associated peaks due to the broken symmetry of the lattice. The frequencies and intensities of these additional modes can be qualitatively estimated using a simple photoelastic coupling model. Shifts in the defect mode frequencies are observed when the spatial location of the defect layer is moved from the substrate to the air interface.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.104459

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2

Digitale Medien

Determination of the (100) InAs/GaSb heterojunction valence-band discontinuity by x-ray photoemission core level spectroscopy (1987)

Gualtieri, G. J. ; Schwartz, G. P. ; Nuzzo, R. G. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 61 (1987), S. 5337-5341

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: The valence-band discontinuity ΔEv has been determined for the (100) InAs/GaSb system by x-ray photoemission core level spectroscopy. For 20 A(ring) of InAs on GaSb we find that ΔEv=0.53 eV. The reverse structure, consisting of a 20-A(ring) layer of GaSb on InAs, gave a measured value of ΔEv=0.48 eV. Since the difference in these two values lies within our experimental uncertainty, we report an average offset of 0.51±0.1 eV. The large value of the valence-band discontinuity in this system shows the band lineup to be of the broken gap variety with the InAs conduction-band energy lying below that of the GaSb valence band. This result is in good agreement with theoretical predictions.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.338270

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3

Digitale Medien

X-ray and Raman characterization of AlSb/GaSb strained layer superlattices and quasiperiodic Fibonacci lattices (1988)

Macrander, A. T. ; Schwartz, G. P. ; Gualtieri, G. J.

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 64 (1988), S. 6733-6745

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Double-crystal rocking curves of samples grown on (001)-oriented GaSb substrates by molecular-beam epitaxy have been analyzed by fitting computer simulations to data for the symmetric (004) and (002) reflections and for asymmetric (115) reflections. Rocking curves revealed a multiplicity of superlattice diffraction peaks. Dynamical diffraction theory using Abeles matrix method [D. W. Berreman, Phys. Rev. B 14, 4313 (1976)] was applied for the symmetrical reflections. We compare our results to standard kinematical simulations, and we find that there are significant differences. For the asymmetric reflections a new dynamical computer simulation code [D. W. Berreman and A. T. Macrander, Phys. Rev. B 37, 6030 (1988)] involving an 8×8 matrix solution of Maxwell's equations was used. Lattice incoherency was determined from measurements of the in-plane mismatch. Dramatic diffraction peak broadening was observed for incoherent superlattices, and this broadening was attributed to a mosaic structure formed by misfit dislocations. Peak broadening was used to infer both a growth direction as well as an in-plane coherence length. The in-plane coherence length was found to be somewhat less than the mean distance between misfit dislocation lines. Mosaic broadening of diffraction peaks of a quasiperiodic lattice was found to be qualitatively similar to that observed for the periodic superlattices. Raman measurements of zone-folded acoustic phonon spectra yielded superlattice periods that agreed with the x-ray measurements within a few percent. Analysis of Raman peak intensities to yield individual layer widths was not found to be quantitative within the confines of current analytic models.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.342005

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4

Digitale Medien

Schottky barrier height variations on the polar (111) faces of n-GaP (1985)

Schwartz, G. P. ; Gualtieri, G. J.

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 58 (1985), S. 4621-4625

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Current-voltage, capacitance-voltage, and photoresponse measurements have been reexamined on the polar Ga-(111)A and P-(∼(111)) B surfaces of n-GaP for reactive (Al) and nonreactive (Ag) metals. Using a chemical etching/in vacuo desorption cleaning sequence, nearly oxide-free A and B faces could be obtained. For diodes formed on such surfaces, the intrinsic, face-dependent variation in A and B Schottky barrier heights was less than 30 meV.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.336231

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5

Digitale Medien

Erratum: "X-ray and Raman characterization of AlSb/GaSb strained layer superlattices and quasiperiodic Fibonacci lattices'' [J. Appl. Phys. 64, 6733 (1988)] (1989)

Macrander, A. T. ; Schwartz, G. P. ; Gualtieri, G. J.

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 66 (1989), S. 3963-3963

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.344504

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6

Digitale Medien

Critical layer thickness and strain relaxation measurements in GaSb(001)/AlSb structures (1989)

Gossmann, H.-J. ; Davidson, B. A. ; Gualtieri, G. J. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 66 (1989), S. 1687-1694

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Measurements of critical layer thicknesses and strain relaxation have been made for AlSb single layers and GaSb/AlSb superlattices on GaSb(001) using ion scattering/particle-induced x-ray techniques, x-ray diffraction, and Raman scattering. The ion beam techniques and x-ray diffraction indicate a critical thickness on the order of 100–170 A(ring). Raman scattering from superlattice samples using 5145 A(ring) excitation shows the most rapid strain relaxation versus layer thickness and indicates a lower apparent critical thickness on the order of 50–100 A(ring). The influence of the finite experimental resolution is addressed. The experimental critical thickness and the strain relief are compared to theoretical models. The equilibrium critical thickness of these models is consistent with the experimental value, indicating that metastable strain retention is not a dominant process in the GaSb(100)/AlSb system under the present growth conditions.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.344387

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7

Digitale Medien

Conductive silver-epoxy pastes: characteristics of alternative formulations (1984)

Franey, J. P. ; Graedel, T. E. ; Gualtieri, G. J. ; [weitere]

Springer

Journal of materials science 19 (1984), S. 3281-3286

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ISSN: 1573-4803

Quelle: Springer Online Journal Archives 1860-2000

Thema: Maschinenbau

Notizen: Abstract Conductive silver-epoxy formulations containing 52 and 62 wt % silver flakes have been prepared and exposed to corrosive environments simulating as much as several decades of typical field exposure. The samples were then analysed by a variety of techniques and the results compared with previous data on pure silver and on a 72 wt % formulation. The corrosive sulphur gas diffused readily into the formulations to form silver sulphide at the surface of the flakes. Contact resistance values initially decreased with time, apparently as a result of softening and increased conductivity of the formulations due to water vapour adsorption. Contact resistance values were lower for high humidity exposure in the presence of H2S than in its absence, suggesting that the effect of water sorption is enhanced by dissolved H2S. The results indicate that low contact resistances and stable electrical performance are not reached within reasonable field lifetimes for these formulations, even though their characteristics are not markedly affected by corrosive environments.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00549816

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8

Digitale Medien

The morphology and corrosion resistance of a conductive silver-epoxy paste (1981)

Franey, J. P. ; Graedel, T. E. ; Gualtieri, G. J. ; [weitere]

Springer

Journal of materials science 16 (1981), S. 2360-2368

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ISSN: 1573-4803

Quelle: Springer Online Journal Archives 1860-2000

Thema: Maschinenbau

Notizen: Abstract Among the important properties of conductive silver-epoxy pastes are their relatively low internal electrical resistance and their low rate of sulphidizing relative to pure silver. To investigate these properties in more detail and to gain understanding of the physical mechanisms involved, paste and bulk silver samples have been exposed to a controlled corrosive atmosphere of hydrogen sulfide and water vapour in purified air. The exposed samples were then analysed by a variety of surface and bulk techniques. The results demonstrate that (1) although the contact resistance of the bulk silver is initially much lower than that of the conductive paste, it increases much more rapidly with long exposure to corrosive atmospheres than that of the paste; this is especially true at low contact probe forces, (2) the hydrogen sulfide permeation constant through a free-standing film of unsilvered paste is (7.0±0.3)×10−2 barrers: sufficiently low that transport of H2S into the bulk paste is strongly inhibited, (3) silver flakes projecting outward from the surface of the paste have little or no resin coating. Corrosion thus occurs on the surface of the material but is inhibited within the material. The relative softness of the material allows contact probe penetration into the uncorroded bulk matrix. As a result, little decrease in the conductivity of the paste occurs even after extended exposures to a corrosive environment.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF01113570

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