An original process to grow cm-squared stress-free 3C-SiC layer is described here. Based on the carburization of silicon nanopillars at relatively low temperature (1150 °C) with methane, the process uses the outdiffusion mechanism of silicon atoms through silicon carbide. After the growth at high pressure of a very thin silicon carbide layer (3 nm), the pressure is decreased to enhance the outdiffusion of silicon through the SiC layer, and thus grow a stress free, 450 nm-thick SiC layer on top of silicon nanopillars. The crystalline quality of the as-grown 3C-SiC layer is good (FWHM of 3C-SiC TO-mode=10 cm−1), despite the presence of stacking faults. This original process could be used to grow by epitaxy a free-standing 3C-SiC layer of high crystalline quality.
The microstructure and electrical properties of varistors, which are composed of ZnO-Pr6O11-CoO-Cr2O3-Dy2O3 (ZPCCD)-based ceramics, were investigated in the range of 0.0–2.0 mol% Dy2O3. As Dy2O3 content is increased, the density was decreased in the range of 5.53–4.43 g/cm3 and the average ZnO grain size was decreased in the range of 18.6–4.7 μm. The varistors with Dy2O3 exhibited a high nonlinear exponent above 30, compared with that without Dy2O3. The incorporation of Dy2O3 significantly improved the nonlinear properties of ZPCCD-based varistors. The varistor with Dy2O3 content of 0.5 mol% exhibited the highest nonlinearity, in which a nonlinear exponent is 66.6 and a leakage current is 1.2 μA. The donor concentration and the density of interface states were decreased in the range of 4.19×1018–0.33×1018/cm3 and 5.38×1012–1.74×1012/cm2, respectively, with increasing Dy2O3 content.
