The preparation and characterization of ultra-thin silicon dioxide films on a Mo( 110) surface

Ultra-thin silicon dioxide films have been deposited on an oxygen-covered Mo(ll0) surface at room temperature by evaporating silicon in an oxygen background (1 X 10W5 Torr). The growth mechanism and structural properties of the 50, films were characterized with temperature programmed desorption, Auger electron, electron energy loss, and infrared reflection-absorption spectroscopies. The interaction of oxygen with Mo010) was also investigated. The SiO, films grow a complete first layer before the growth of bulk film at room temperature. The gas phase precursor for the SiO, film is SiO, produced by oxidative etching of silicon. The as-deposited SiO, films are proposed to consist of short-ranged networks of [SiO,]. Upon annealing to 1400 K, the small networks of [SiO,] fuse together, with the films assuming the electronic and bonding structures of vitreous silica. The SiO, films are thermally stable up to 1600 K with stability increasing with film thickness. At high temperatures, silicon dioxide is reduced by the MO substrate to form volatile SiO and MOO,.