Structure and Composition of Titanium Nanocluster Films Prepared by a Gas Aggregation Cluster Source

Structure and composition of titanium nanocluster films were studied on samples prepared by a gas aggregation cluster source based on a planar magnetron following the Haberland concept. Elemental composition of the nanoclusters was studied by X-ray photoelectron spectroscopy (XPS), their crystal structure was determined by X-ray diffraction, and their optical properties were characterized by UV–vis spectroscopy. Both as-prepared (without any additional postdeposition treatment) and annealed films were studied. Annealing of selected nanocluster films was done in air at 420 °C for 1 h followed by a natural cool-down. Titanium nanocluster films were found to oxidize immediately when exposed to ambient atmosphere. The as-prepared nanoclusters were composed of both Ti and TiO2. The nanoclusters undergo further oxidation in time and their structure and properties change. The transformation from a metal to an oxide structure of the nanoclusters upon annealing ends up in a semistable anatase crystal form of TiO2 with traces of a thermodynamically stable rutile crystal form.