HIGH-TEMPERATURE AIR-ANNEALING BEHAVIOR OF SPUTTER DEPOSITED AMORPHOUS YTTRIA FILMS ON FUSED-SILICA

This article addresses the response of amorphous yttria films grown on fused silica substrates to high temperature (900-degrees-C) cyclic annealing in air for up to 145.5 h. Surface science and bulk analytical techniques were applied to determine and correlate changes in microstructure, crystallization, optical behavior, and chemistry (atomic concentration and bonding) concurrent with annealing. Limited crystallization occurred after short-term annealing, resulting in regions of nanocrystallinity in an amorphous matrix. X-ray photoelectron spectroscopy data showed an accompanying loss of resolution of Y 3d5/2 - 3d3/2 spin states, but no change in the fundamental optical absorption edge was observed. Long-term annealing resulted in granularization of the matrix itself, with a large increase in optical absorption in the 3-5 eV range. X-ray photoelectron spectroscopy data showed a broadening of the O 1s peak. No evidence of Si diffusion from the interfacial region into the yttria film was seen, even after long-term annealing, demonstrating amorphous yttria's potential use as a high temperature diffusion barrier for metal-on-Si-based ceramic applications.