Synthesis and characterization of titania films on Mo(110)

Ultra-thin titania films were grown on a Mo(1 1 0) substrate by vapor depos iting Ti in an O-2 ambient (5 x 10(-7) Torr) at 600 K, followed by annealin g to 900-1200 K. X-ray photoelectron spectroscopy showed that titanium oxid e films annealed to 900 K were partially reduced, exhibiting Ti4+, Ti3+ and Ti2+ species, whereas films annealed to 1200 K were fully oxidized and exh ibited only Ti4+. Corresponding scanning tunneling microscopy measurements revealed layer-by-layer growth of titania films on Mo(1 1 0) at 900 K. Flat terraces with three different orientations were observed. The line spacing s between the neighboring atomic rows for all terraces were similar to6.5 A ngstrom, suggesting epitaxial growth of TiO2(1 1 0)-(1 x 1). A further anne al of the films to 1200 K led to three-dimensional, rough surfaces for the fully oxidized films, indicating the formation of stable crystallites at hi gh temperature. (C) 2001 Elsevier Science B.V. All rights reserved.