Selvedge layer in the interface of Pd thin film with YSZ substrate

Abstract

Widespread application of YSZ ionic conductor in today's technology requires electrodes to collect charges. These electrodes should represent high electrical conductivity, appropriate adhesive properties and depending upon the application, they have to be porous. The choice of suitable material becomes narrow when YSZ exhibits a metastable tetragonal phase transition at its working temperature. Palladium, as a promising material, represents these properties even though it suffers from interfacial mixing during deposition. This study is an effort to understand the effect of substrate temperature upon interfacial properties of Pd films deposited over YSZ substrate.In this study, Pd–O selvedge layer was detected in between Pd thin film and YSZ substrate. Basically, oxygen atoms migrate into interface either from ambient or substrate stress relaxation. Large concentration of oxygen atoms in the interface confirms the consequence of substrate stress relaxation. Substrate relaxation is accompanied with metastable phase transition in which oxygen displacement results into upward diffusion of oxygen atoms. Since diffusion is a thermally activated phenomenon, variation of substrate temperature could lead to monitoring of oxygen diffusion into Pd layer. Moreover, extra efforts on controlling this phenomenon may result in generation of spontaneously formed homogenous buffer layer which can act as diffusion barrier.