Stability of the YBa2Cu3O7−x−Si interface

Abstract

Electron spectroscopies were used to study the reaction of Si and SiO2 layers with high-Tc superconductors at room temperature and under annealing conditions. The superconductor samples include YBa2Cu3O7 ceramic and thin film samples as well as GdBa2Cu3O7 ceramic samples. The results show that the Si overlayers withdraw oxygen from the superconductor and form an interfacial layer of Si oxide at room temperature. Annealing increases the reaction rate so that films as thick as 30 Å become completely oxidized following annealing above approximately 100 °C. Ba segregates to the surface from the bulk after Si oxidation when annealed at temperatures higher than 200 °C, while the rare earth element (Gd) does not segregate.