Structural and Electrochemical Properties of ZrO₂·H_x Thin Films Deposited by Reactive Sputtering in Hydrogen Atmosphere as Solid Electrolytes

Abstract

The feasibility of applying ZrO2·Hx thin films as solid electrolytes in solid-state ionic energy systems, such as solid oxide fuel cells and supercapacitors was studied. ZrO2·Hx thin films were deposited on Pt/Ti/SiO2/Si substrates by radio-frequency reactive sputtering with various hydrogen volume fractions in reactive gas. With a variation in hydrogen volume fraction, the surface roughness of the as-deposited films increased. In addition, the structure of the as-deposited films grew in the [111] direction with an increase in hydrogen volume fraction. By Rutherford backscattering spectrometry (RBS) and secondary ion mass spectrometry (SIMS) studies, the Zr/O ratio and hydrogen distribution were evaluated. On the basis of a sample structure of Pt/ZrO2·Hx/Pt/Ti/SiO2/Si for measuring an electrochemical property, an impedance measurement conducted at room temperature revealed an ionic conductivity of 1.67 ×10-6 S/cm, suggesting that ZrO2·Hx thin films can possibly be used as solid oxide thin film electrolytes in all solid-state ionics power devices requiring a hydrogen conducting electrolyte.