MECHANISM OF INCONGRUENT ABLATION OF SRTIO3

At low fluences, the [Sr]/[Ti] ratio of laser deposited SrTiO3 films a ppears to be a function of the laser fluence. The deviation from stoic hiometry 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 (ab ove 1.3 J/cm(2)), stoichiometric SrTiO3 films are obtained. This is no t due to a change in ablation mechanism, but follows from the fact tha t at 1.3 J/cm(2) the calculated diffusion length of Sr within the irra diated target, becomes of the order of the ablation rate per shot. (C) 1998 American Institute of Physics.