Phase selectivity upon flash-lamp annealing of sputter deposited amorphous titanium oxide films

We report the impact of flash-lamp-annealing (FLA) on the structural evolution of amorphous titania (TiO₂) films produced by DC reactive magnetron sputtering. TiO₂ films were grown at room-temperature at different oxygen partial pressure (P_O2) and subsequently annealed as a function of the FLA energy density. X-ray diffraction confirms that FLA induces phase formation from the initial amorphous state with a general transition from anatase to rutile by increasing the FLA energy density (temperature). Interestingly, the transformation onset of anatase to rutile is achieved at lower energy densities for higher P_O2. On the contrary, films with a highly resilient anatase phase can be produced at relatively low P_O2. A detailed analysis of the pristine amorphous structure carried out by X-ray absorption near-edge structure indicates the role of oxygen sites in the observed phase transformation. In particular, oxygen vacancies seem to stabilize the anatase phase at high temperatures. The results show the relevance of subtle changes in the initial amorphous structure for phase selectivity in TiO₂ films upon FLA.