Hydrogen-induced degradation in epitaxial and polycrystalline (Ba,Sr)TiO3 thin films

Abstract

A comparative study of hydrogen-induced degradation in epitaxial and polycrystalline $(\mathrm{Ba,Sr}){\mathrm{TiO}}_3$ (BST) thin films has been carried out. Epitaxial BST was prepared on ${\mathrm{SrRuO}}_3$ $(\mathrm{SRO}\mathrm{)/}{\mathrm{SrTiO}}_3$ (STO), whereas polycrystalline BST was deposited on ${\mathrm{SRO/SiO}}_x/\mathrm{Si}.$ After the Pt top electrode deposition, we have measured the dielectric response and leakage current characteristics before and after annealing in forming gas (6% hydrogen/94% argon) at $\text{450\hspace{0.05em}°}\mathrm{C}$ for 1 h. Even though both samples have the same capacitor architecture, Pt/BST/SRO, the degree of degradation after annealing in forming gas was found to be quite different. Epitaxial BST films were highly immune to hydrogen degradation; however, polycrystalline BST films degraded severely in terms of both dielectric and electrical properties. We show that the grain boundary is one of the main sources of hydrogen-induced degradation.