Pressure effects during pulsed-laser deposition of barium titanate thin films

The composition and homogeneity of barium titanate films grown by pulsed-laser deposition at different substrate temperatures (room temperature, 700 degrees C) and gas environments (O-2, Ar) in a broad pressure range (10(-7)-1 mbar) are correlated to the plasma expansion dynamics. It is found that the deposited films present an excess of Ba in the intermediate pressure range (10(-2) < P < 10(-1) mbar) and a peaked distribution of Ba to Ti atoms ratio, that is not related to either the substrate temperature or the nature of the gas environment. The results are discussed in terms of the dependence of the plume length (L-P) On the gas pressure and the existence of scattering processes for distances (d) from the target lower than L-P and the diffusion of the ejected species for L-P < d.