Study of Oxidation of Thin Ti Film Controlled by Reduction Processes in Water Vapor Plasma

Abstract

Changes of microstructure, phase composition and surface morphology were investigated for 200-700 nm thick Ti films, which were deposited on Si substrates using magnetron sputtering technique and treated at pressure of 5-10 Pa by water vapor plasma with the plasma processing power in the range of 20-300 W. Depth profiling of oxygen and hydrogen atoms across the thickness of plasma treated Ti films, surface height nanotopography and four-point probe resistivity measurements have been performed complementary to the analysis of phase and compositional changes registered by XRD and EDS techniques, respectively. It is shown that the different reduction/oxidation state on the surface can be maintained by coordinated adjustment in plasma power. Due to strong coupling of adsorbed water clusters to hydrophilic titanium oxide, a fast and complete transformation of Ti into TiO2 accompanied by film cracking and spontaneous lifting in the form of "popping off" discrete blisters was observed. Analysis of the experimental results is used to obtain important insights on the behavior of water molecules adsorbed on the reduced titania surfaces exposed to water vapor plasma at room temperature.