Target modification in the excimer laser deposition of YBa2Cu3O7−x thin films

Under conditions used for pulsed laser deposition (308 nm, 20 ns, 2–8 J/cm2) of Y-Ba-Cu-O superconducting thin films, we have measured a pronounced decrease in deposition rate with cumulative laser exposure of the target. This decay in rate is accompanied by evolution on the target surface of microscopic columnar structures, having yttrium-enriched surfaces, which are aligned in the direction of the incident laser beam (45°). Neither the vapor plume direction nor film stoichiometry is affected by the presence of these oriented, chemically altered surface features.