Papers by Author: Miwa Kawasaki

Abstract: We investigate the effect of surface orientation and off-angle for Al-implanted 4H-SiC samples after high temperature annealing. The samples are obtained from a 4H-SiC (0001) substrate 8° off-angled (Si-face 8°off), and (000-1) substrates 8° (C-face 8°off), 4° (C-face 4°off) and less than 1° off-angled (C-face ~1°off). An n-type epitaxial layer is deposited on all substrates. Multiple implantations of Al+ (30~200keV) are carried out at 600°C. The total dose is 8.6 × 1015 cm-2. The Al-implanted samples are annealed in Ar ambient at 1580°C, 1700°C and 1800°C for 30s using the hybrid super rapid thermal annealing (HS-RTA) equipment. In this study, sheet resistance (Rs), free carrier concentration (Ns), Hall mobility (μ) and root-mean square roughness (Rrms) are used to evaluate the Al-implanted samples after high temperature annealing. Rs for all Al-implanted samples after annealing at 1800°C for 30s is around 18k/. Rrms for the Al-implanted C-face samples after annealing at 1800°C increases with increasing off-angle. Rrms for the Al-implanted Si-face 8°off sample after annealing increases with annealing temperature. Rrms for the C-face ~1°off Al-implanted sample after annealing at 1800°C is lower than that for the Si-face 8°off Al-implanted sample after annealing at 1700°C, moreover Rs for the C-face ~1°off sample after annealing at 1800°C is about 10% of that for the Si-face 8°off Al-implanted sample after annealing at 1700°C. It is shown that the C-face ~1°off sample is useful to fabricate a p+ region with low Rs and low Rrms. If C-face 4H-SiC is used to fabricate devices, devices made on C-face 4H-SiC with low off angle are expected to decrease any problems caused by increase of surface roughness after high temperature annealing (~1800°C).

Abstract: The photocatalytic effects of 4 samples, which TiO2 layer uniformly coated on Al fiber, are evaluated by NOx removal. An anatase TiO2 coating with good crystal quality and high Ti content exhibits the best photocatalytic effect on NOx removal. It is coincidence with the results of XRD, XPS results for 4 samples. The photocatalytic ability is enhanced by the introduction of H2O2 due to the formation of large amount OH radicals.