SiO2 and Si3N4 passivation layers on Y-Ba-Cu-O thin films

Abstract

High‐T_c Y‐Ba‐Cu‐O superconductor thin films were passivated with thermally evaporated SiO₂ or rf magnetron sputtered Si₃N₄. Thermal evaporation of SiO₂ on the Y‐Ba‐Cu‐O thin‐film surface did not degrade the zero resistance temperature of Y‐Ba‐Cu‐O films. A seriously lowered zero resistance temperature of Y‐Ba‐Cu‐O films was found if Si₃N₄ was sputtered onto the Y‐Ba‐Cu‐O film surface. A one month exposure of the Y‐Ba‐Cu‐O film to the environmental air did not change the T_c onset of the superconductor thin film but gave a slight decrease of T_c zero with SiO₂ as the surface passivation layer. High‐frequency capacitance‐voltage studies were made on metal‐insulator‐superconductor to investigate the interface and surface properties of Ya‐Ba‐Cu‐O thin films. The experimental data suggested that a very thin layer semiconductor phase Y‐Ba‐Cu‐O was produced between Y‐Ba‐Cu‐O films and the insulator films during the deposition of the passivation film onto the Y‐Ba‐Cu‐O surface.