Scanning tunneling microscopy study of surface reconstructions of rutile TiO2(111)

Structure of the rutile TiO2(111) surface prepared in ultra-high vacuum (UH V) was investigated by scanning tunneling microscopy (STM) and low-energy e lectron diffraction (LEED) for the first time; It is expected from the crys tal structure that the stoichiometric TiO2(111) surface has more separated Ti metal sites compared to the well-studied rutile TiO2(110) surface. When the surface was annealed at 1024 K in UHV without Ar+ ion sputtering, a pha se indexed as ((1)(-1)(1)(1)) was observed where atomic-scale protrusions ( probably Ti atoms) were ordered rectangularly After several cycles of Ar+ i on sputtering and annealing up to 976 K, (1 x 1) and double-domain (1 x 2) small patches appeared on the surface. These three phases were unstable aga inst high-temperature annealing in vacuum, probably because they are sensit ive to surface stoichiometry.