Ultra-thin Si overlayers on the TiO2 (110)-(1x2) surface:: Growth mode and electronic properties

The growth of thin subnanometric silicon films on TiO2 (110)-(1 x 2) reconstructed surfaces at room temperature (RT) has been studied in situ by X-ray and ultra-violet photoelectron spectroscopies (XPS and UPS), Auger electron and electron-energy-loss spectroscopies (AES and ELS), quantitative low energy electron diffraction (LEED-IV), and scanning tunneling microscopy (STM). For Si coverage up to one monolayer, a heterogeneous layer is formed. Its composition consists of a mixture of different suboxides SiOx (1 < x <= 2) on top of a further reduced TiO2 surface. Upon Si coverage, the characteristic (1 x 2) LEED pattern from the substrate is completely attenuated, indicating absence of long-range order. Annealing the SiOx overlayer results in the formation of suboxides with different stoichiometry. The LEED pattern recovers the characteristic TiO2 (110)-(1 x 2) diagram. LEED I-V curves from both, substrate and overlayer, indicate the formation of nanometric sized SiOx clusters. (c) 2006 Elsevier B.V. All rights reserved.