Mechanism of incongruent ablation of SrTiO3

At low fluences, the [Sr]/[Ti] ratio of laser deposited SrTiO3 films appears to be a function of the laser fluence. The deviation from stoichiometry is remarkably constant in time. From an analysis of both the composition of the film and the irradiated target, we deduce a volume-diffusion-assisted preferential ablation process. At high fluences (above 1.3 J/cm(2)), stoichiometric SrTiO3 films are obtained. This is not due to a change in ablation mechanism, but follows from the fact that at 1.3 J/cm(2) the calculated diffusion length of Sr within the irradiated target, becomes of the order of the ablation rate per shot. (C) 1998 American Institute of Physics.