Surface compositional and topographical changes resulting from excimer laser impacting on YBa2Cu3O7 single phase superconductors

Abstract

Superconducting pressed pellets of YBa₂Cu₃O₇ (T_c=90 K), which were used as ablation targets for laser‐induced vapor deposition of high T_c(85 K) superconducting thin films, have been analyzed by secondary electron microscopy, scanning Auger microscopy, energy dispersive x‐ray analysis, and x‐ray diffractometry. The elemental distribution of Y, Ba, and Cu appears reasonably uniform at depths corresponding to that probed by energy dispersive x‐ray analysis (∼1 μm). However, scanning Auger microscopy analysis of the laser‐impacted area shows a significant depletion of Cu and spatial redistribution of Y, Ba, Cu, and O on the target surface. X‐ray diffractometry of the laser‐impacted area shows the appearance of a new broad peak at a diffraction angle 2θ=29.7°, characteristic of BaY₂O₄ and a poorly defined peak at 2θ=29.3°, that can be attributed to BaCuO₂. A possible influence of the laser‐induced bulk superconductor compositional changes on the film composition is discussed in relation to recently reported experimental results on laser vapor deposition of high T_c films.