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Interfacial microstructure of In/Pd ohmic contacts to n-GaAs was studied by various X-ray diffraction techniques and secondary ion mass spectroscopy (SIMS). Analysis of this interface after various annealing showed that In1-xGaxAs compounds are formed at the interface and the composition of these compounds depends upon the annealing temperature. As the temperature increases, the stoichiometry of the Inrich compounds tends toward higher concentrations of Ga. The low contact resistance is achieved by dividing the Schottky barrier between metal and GaAs into two barriers due to metal/Inl-xGaxAs and In1-xGaxAs/GaAs. The barrier due to In1-xGaxAs/GaAs is believed to be the main limiting factor in lowering of contact resistance. The observed ohmic behavior for sample annealed at 500°C for 20 s is attributed to the further reduction of this barrier.
Several compositions of Al-Pt thin films have been co-evaporated on GaAs substrates to study the stability of the alloys at high-temperature anneals. The Al concentration in the alloys ranges from 45 at.% to 70 at.%, and we show that the films meet thermal stability requirements imposed by GaAs self-aligning gate technology for compositions between AlPt and Al2Pt.
We show that the decagonal Al3Pd phase can be formed by solid state reaction in lateral and conventional thin film couples of Al and Pd. The metastable decagonal phase forms after the initial growth of the Al3Pd2 compound.
Several compositions of A1-Pt thin films have been co-evaporated on GaAs substrates to study the stability of the alloys at high-temperature anneals. The A1 concentration in the alloys ranges from 45 at.% to 70 at.%, and we show that the films meet thermal stability requirements imposed by GaAs selfaligning gate technology for compositions between AIPt and Al2Pt.
Internal stresses are measured in CVD diamond coatings deposited on a variety of substrate materials by low incident beam angle X-ray diffraction and by micro-Raman spectroscopy. The X-ray diffraction technique gives an integral stress value over a comparably large coating area whereas the Raman technique results in localized stress information with a lateral resolution of down to 1 µm. The stress values obtained from both methods compare well for diamond coatings of 6 μm thickness whereas a difference is observed for thicker coatings.
Dissolution of ZrO2 oxide in synthetic CaO - Al2O3 - SiO2 -
Na2O - B2O3 mould fluxes was investigated in situ using a
Confocal Scanning Laser Microscope (CSLM). Evolution of
particle radius with time is obtained exhibiting strong dependence
on temperature and basicity of the mould fluxes. The
rate-limiting step of the dissolution process was discussed, and
basicity was shown to significantly influence the rate-limiting step.
Two experimental techniques for the quantitative measurement of residual stress in thin polycrystalline diamond coatings have been developed. The x-ray low-incident-beam-angle-diffraction (LIBAD) allows one to measure the lattice strain with well-defined in-depth information, while micro-Raman spectroscopy permits one to accurately measure the frequencies of the zone-center optical phonons of diamond which are related to the lattice strain. The interpretation of the measured information in terms of residual stress is outlined for both techniques. The residual stress data obtained by either method in thin CVD diamond coatings were found to be in excellent agreement. The sign and magnitude of the balanced biaxial stress in the coating plane depend mainly on the substrate material used for the diamond deposition. Compressive stress was present in diamond coatings deposited on WC-Co substrates, whereas tensile stress was found in those on SiAlON substrates.
This paper is aimed at understanding the tribo-oxidation of a physical vapor-deposited TiN coating when sliding against a corundum ball. This is achieved through a compositional and structural analysis of the wear debris. Wear debris particles generated at three different sliding speeds were analyzed with micro-Raman spectroscopy, transmission electron microscopy, and electron probe microanalysis. The analysis showed that the wear debris when formed at the low and medium sliding speed consist of TiO2 with a nanocrystalline structure containing both anatase and rutile structural elements. Only rutile structural elements could be observed in the debris formed at the high sliding speed. These results on the characterization of the wear debris are interpreted with calculations of the flash temperature in the tribo-contact and with recent ball-on-disk results on the wear rate of TiN as a function of the sliding speed to propose a mechanistic view of the tribo-oxidation and wear process. The relation with previous and recent experimental results on the static oxidation of TiN is also given.
Al films deposited on Pt layers developed voids after annealing at 250 °C. The amount of Al in the area surrounding the voids increased relative to the as-deposited film. The addition of 1 or 4% Cu to the Al suppressed the void formation and lateral Al migration. The void formation is related to compound formation with the Pt. The addition of Cu to the Al did not modify the Pt2Al3 formation.
Solid-state amorphization is reported to occur in aluminum-platinum thin films. A uniform amorphous alloy layer was observed at the interface between aluminum and platinum layers for electron beam evaporated samples in an as-deposited state. For a pure aluminum overlayer deposited on top of a coevaporated Al–Pt amorphous alloy, the aluminum dissolves into the amorphous phase leading to a fully amorphous sample. In this last case the amorphization is nonuniform upon low-temperature anneals (T < ≃2 200 °C) and gives rise to hole formation in the aluminum overlayer. Direct observations of this phenomenon during in situ annealing of the thin films in a transmission electron microscope were carried out.
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