RAMAN-SCATTERING STUDY OF [HHK]-GAAS/[SI OR CAF(2)] STRAINED HETEROSTRUCTURES (VOL 76, PG 2773, 1994)

International audienceno abstrac

MBE growth and Raman analysis of [hhk]GaAs (Si or CaF2) highly strained heterostructures

International audienceno abstrac

RAMAN-SCATTERING STUDY OF [HHK]-GAAS/(SI OR CAF2) STRAINED HETEROSTRUCTURES

International audienceno abstrac

AU AND AU-ZN CONTACTS ON P-GASB AND THE CHARACTERISTICS OF THE INTERFACES

We analyse the specific contact resistance rho(C) and the interfacial microstructural characteristics (by Auger electron spectroscopy and X-ray diffraction) of Au and AuZn contacts on p-GaSb. The experiments showed that rho(C) hardly depends on the inclusion of Zn in the metallic film or on the annealing processes, at least for the carrier concentrations available (p greater-than-or-equal-to 1.6 x 10(17) cm-3). However, the dependence of rho(C) on the acceptor concentration leads us to conclude that field emission is the principal conduction mechanism, The efficacy of an Ar glow discharge in considerably reducing the oxide present at the GaSb substrate is demonstrated. We also show that rapid thermal annealing produces much thinner interface-reacted layers than does the conventional (resistive) heat treatment.20332833

Catalytic partial oxidation and steam reforming of methane on La2O3-Al2O3 supported Pt catalysts as observed by X-ray absorption spectroscopy

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Structural transformations of Pt supported on Al2O3 or La2O3-Al2O3 were studied by X-ray absorption near edge structure (XANES) at the Pt L-3 edge during heating and cooling under partial oxidation of methane (POM) conditions, and by extended X-ray absorption fine structure (EXAFS) under steam reforming of methane (SRM) conditions. Ignition of the POM reaction occurred simultaneously with the reduction of PtO2 to metallic Pt, indicating that the ignition occurs on metallic Pt. When the temperature of the POM reaction was decreased, carbon accumulated on the metallic Pt surface, and the activation of CH4 was suppressed at about 370 degrees C. Nevertheless, the oxidation of carbon remaining on the metallic Pt surface continued until a temperature of around 270 degrees C was reached, when oxidation of Pt occurred and the oxidation reactions were extinguished. The EXAFS data obtained during SRM and under H-2 suggest that complex alterations in the structure of Pt particles occur with changes of temperature and reactant composition. The SRM activity of Pt catalysts depends on both the access of CH4 to active Pt sites, and the changes in the structure of Pt particles under reaction conditions. For both reactions, Pt supported on La2O3-Al2O3 was more stable than Pt supported on Al2O3, indicating a higher stability of Al2O3 modified with La2O3. (c) 2012 Elsevier B.V. All rights reserved.4317987Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Brazilian Synchrotron Light Laboratory (LNLS, Campinas, Brazil)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES