Characterization of Ti/Al Ohmic Contacts to p-Type 4H-SiC Using Cathodoluminescence and Auger Electron Spectroscopies

We have used depth-resolved cathodoluminescence and Auger electron spectroscopies, DRCLS and AES, respectively, to probe the electronic structure and the composition of Ti/Al ohmic contacts to p-type SiC on a nanometer scale. A continuous Ti-Si-C compound layer was observed using the Auger depth profile. No interfacial Al segregation was found. The secondary electron threshold technique showed a continuous decrease in work function from the p-type SiC to the Ti-Si-C compound layer. Our results support an ohmic contact mechanism by an intermediate semiconductor layer which reduces the otherwise large interfacial Schottky barrier height. DRCLS revealed a ~2.78 eV sub-band gap transition enhanced by interfacial reaction in the near-interface SiC, suggesting the formation of additional C or Si vacancies.

Erosion Behavior of Silicon Nitride with Graded Microstructure

Silicon nitride has been considered as candidate tribological material due to their excellent mechanical and thermal properties. This study investigated the effect of graded grain size on the erosion behavior of silicon nitride at room and high temperatures. Erosion tests were carried out with a gas blast-type erosion tester at temperatures up to 800 °C. Weight loss after impact of SiC particles were measured. The erosion rate varied with temperature and microstructure. Different erosion behavior depending on microstructure were discussed based on SEM observation Auger depth profile of worn surfaces.

Growth of PbTe films by magnetron sputtering

ABSTRACTThin films of PbTe were deposited on Si (111) wafers and glass substrates at a constant power for different times and at a constant time at various power levels. In some cases substrate heating to a temperature of ∼673K was performed during sputtering. Structural analysis by Xray diffraction (XRD) and high-resolution electron microscopy (HRTEM) were performed. The composition of the PbTe film was evaluated by Auger depth profile. At an appropriate combination of power and deposition time only (200) and its higher order peaks were observed in the PbTe film. It is expected that it is feasible to obtain epitaxial PbTe film by RF magnetron sputtering.

Aligned Diamond Nanowhiskers

We investigated the formation of nanowhiskers by means of air plasma dry etching using diamond films of two different kinds: as-grown diamond films and films with molybdenum (Mo) deposits. As for the as-grown diamond films, nanowhiskers were found to form preferentially at grain boundaries of diamond crystals. Auger depth profile analysis of the etched films revealed a progressive enrichment by Mo toward the whisker tip, resulting from accidental sputtering of Mo substrate holder. With dry etching of diamond films with preformed Mo deposits, well-aligned whiskers 100 nm in diameter were found to form uniformly over the entire film surface with a population density of 30/μm2. From these findings, it follows that Mo deposits serve as micromasks for the formation of the nanowhiskers. It was also confirmed that these whiskers showed excellent field-emission behavior.

YBa2Cu3O7−x THIN FILMS GROWN ON SAPPHIRE WITH EPITAXIAL YTTRIA-STABILIZED ZrO2 BUFFER LAYER

We have successfully fabricated high-quality YBa 2 Cu 3 O 7−x (YBCO) thin films grown on sapphire with epitaxial Yttria-Stabilized ZrO 2 (YSZ) buffer layer by pulsed laser deposition. X-ray diffraction and Auger depth profile were used to characterize these thin films. The values of zero-resistance temperature Tco and critical current density J c (at 77 K) of c-axis oriented YBCO thin film with 500 Å-YSZ buffer layer were 91 K and 2.2×106 A/cm 2, respectively. The Auger depth profile showed that no obvious diffusion occurred between the buffer layer and the YBCO film. The influence of substrate temperature and thickness of buffer layer has been investigated.