Diffusion of metal ions from a substrate into oxide coatings

Abstract

Concentrations of metal ions from a substrate were found in coatings adjacent to the substrate by studying the coatings using X-ray photoelectron spectroscopy before and after annealing. Small metal ions easily diffused into the coating from the substrate, whereas larger metal ions had more difficulty doing so because of their large atomic radii. A higher annealing temperature and a lower packing density induced a faster diffusion rate and a higher concentration of metal ions in the coating. Smaller metal ions passed through a SiO2 layer and preferentially accumulated in the Ta2O5 layer due to the migration of oxygen vacancies. These results are relevant for selecting the coating temperature, annealing temperature, and the substrate.