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

Abstract

Superconducting pressed pellets of YBa2Cu3O7 (Tc=90 K), which were used as ablation targets for laser-induced vapor deposition of high Tc(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 Tc films.