SURFACE PHASES OF SIC ISLANDS GROWN OVER SI(111)-(7X7) USING C-60 AS A PRECURSOR

One possible way to grow SiC crystals on Si(111) is to deposit C-60 mo lecules at room temperature and subsequently heat at temperatures high er than 800 degrees C, where the C-60 molecule decomposes. As in SiC s ingle crystals, the surface phases exhibited by these islands should a lso depend on the annealing temperature. In this work we present scann ing tunneling microscopy (STM) data that reveals the coexistence of tw o different phases. The first one. with a periodicity of (2 root 3 x 2 root 3) times the SiC(111) lattice parameter, has nor been described previously in the literature, and we have observed it from the first s tages of annealing. The other one, appearing after annealing at higher temperatures, is identified as the (3 x 3) phase reported in previous STM data. Our STM images are strongly bias dependent. probably due to the polar character of the SiC, and make it difficult to obtain the a tomic structure of these phases. (C) 1998 Elsevier Science B.V.