STUDIES OF$4{\rm H}\mbox{--}{\rm SiC}(0001){\rm Si}(\sqrt3\times\sqrt3)$AND (0001)C(3×3) SURFACES AND THEIR METALLIZATION PROCESS BYNIUSING STM, AES AND LEED

Several methods have been tried to prepare clean surfaces of 4H–SiC(0001)Si and C, whose surface atomic, or electronic, structures have been studied by LEED (low energy electron diffraction) STM (scanning tunneling microscopy) and AES (Auger electron spectroscopy). Some sequential chemical treatments, for example, agitation in an organic solvent and dipping in HF solution, followed by the heating of a SiC wafer in UHV (ultrahigh vacuum, below 10-7Pa) at 950°C, gave either a$(\sqrt3\times\sqrt3)$or 3×3 superstructure, observed by LEED (low energy electron diffraction), for the SiC(0001) Si or C surface, respectively. An elongated NH4F treatment followed by a heat treatment in UHV at ~950°C gave a rather flat region to be investigated by STM, where a$(\sqrt3\times\sqrt3)$superstructure for the SiC(0001) Si surface has been observed. In the case of metal (Ni) atom deposition on SiC(0001)${\rm Si}(\sqrt3\times\sqrt3)$and (0001)C(3×3) surfaces, AES and LEED analysis have clarified that deposited metal atoms form islands up to ~5 Å. However, Ni atoms dispersed uniformly at the very beginning of the deposition, which means that the Ni overlayer piles up in layer followed by island growth mode.