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

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Abstract
High‐Tc 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 Tc onset of the superconductor thin film but gave a slight decrease of Tc 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.