ULTRAHIGH-VACUUM METALORGANIC CHEMICAL-VAPOR-DEPOSITION GROWTH AND IN-SITU CHARACTERIZATION OF EPITAXIAL TIO2 FILMS

In a two-chamber ultrahigh vacuum system, epitaxial TiO2 thin films ha ve been deposited by metalorganic chemical vapor deposition on single crystal oxide substrates over a temperature range of 250-800-degrees-C , using titanium (IV) isopropoxide as the precursor. During the initia l stage of epitaxial film deposition, the growing surface quickly plan arized and the film's orientations was determined by the substrate str ucture. This substrate influence is manifested in the growth of anatas e (the low temperature phase of TiO2) on (001) SrTiO3, at high deposit ion temperatures (800-degrees-C), whereas on either (0001) or (1102BAR ) Al2O3 sapphire, epitaxial rutile (the high temperature phase) is for med. In situ Auger electron spectroscopy analyses, before and after gr owth, revealed a film composition identical to that of a bulk TiO2 sta ndard. No carbon contamination was detected in films grown throughout the deposition temperature range. The decomposition mechanism of this precursor that leads to the absence of incorporated carbon in the depo sited film is discussed. X-ray diffraction confirmed the film crystall inity and the structural orientation between the film and substrate. C ross-section transmission electron microscopy showed an abrupt interfa ce between the film and substrate. High tilt angle scanning electron m icroscopy revealed that the surface of the films became increasingly s mooth with increasing growth temperatures. Conditioning the substrate surface at high temperatures in an O2 environment improved the structu ral quality and surface smoothness of the subsequently deposited films .