Dielectric and Microstructural Properties of Ba(Ti1−xZrx)O3 Thin Films on Copper Substrates

Abstract

Barium titanate zirconate, Ba(Ti 1 - x Zr x )O 3 (0 ≤ x ≤ 0.25), thin films were deposited via the chemical solution deposition (CSD) process directly on copper foils. The films were processed in a reductive atmosphere containing water vapor and hydrogen gas at 900°C in order to preserve the metallic copper substrate while crystallizing the film into a perovskite structure. The microstructure and phase transition phenomena of films were studied utilizing x-ray diffraction, atomic force microscopy, and the temperature dependence of the dielectric constant and loss tangent Increasing the fraction of BaZrO 3 revealed several effects, including an increase in unit cell dimensions, a decrease in both the temperature and value of the maximum permittivity, as well as a decrease in the average grain size of the films. Films were analyzed for dispersion in the transition temperature with frequency. Results indicated that films containing 25 mol% BaZrO 3 demonstrate a shift in the temperature of the ferroelectric phase transition with increasing measurement frequency. This shift, combined with the dispersive nature of the transition, suggests that films of this composition are of the relaxor ferroelectric family. The ability to process high permittivity thin film materials directly on inexpensive copper substrates has strong technological implications toward embedded passives and efficient frequency agile devices.