Observation of two distinct components during pulsed laser deposition of high T c superconducting films

Abstract
Using Rutherford backscattering technique, we have measured the angular distribution of the composition and thickness of the Y‐Ba‐Cu oxide film deposited by firing excimer laser (30 ns, 248 nm) pulses at a stoichiometric Y1Ba2Cu3O7−x pellet. The angular distribution consisted of two distinct components: one a cos θ component, a result of evaporation, and the other a highly forward directed component, a result of a secondary ejection process. The evaporated component is nonstoichiometric, as one would expect, whereas the forward‐directed component has a composition close to that of the pellet. Further, the forward‐directed stoichiometric component increases with the laser energy density in comparison with the evaporated component. These observations are discussed in the context of current models of laser‐induced material ejection at surfaces.The laser energy dependence of the deposition is of critical importance in controlling the film stoichiometry.