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(110) surface at room temperature by evaporating silicon in an oxygen background (approximately 1 x 10(-5) Torr). The growth mechanism and structural properties of the SiO2 films were characterized with temperature programmed desorption, Auger electron, electron energy loss, and infrared reflection-absorption spectroscopies. The interaction of oxygen with Mo(110) was also investigated. The SiO2 films grow a complete first layer before the growth of bulk film at room temperature. The gas phase precursor for the SiO2 film is SiO, produced by oxidative etching of silicon. The as-deposited SiO2 films are proposed to consist of short-ranged networks of [SiO4]. Upon annealing to 1400 K, the small networks of [SiO4] fuse together, with the films assuming the electronic and bonding structures of vitreous silica. The SiO2 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 MoO3.