Identification of ZnTiO3 nanostructures in oxidized TiN/ZnS thin films using X-ray absorption spectroscopy

Abstract

We examined the chemical and local structural properties of oxidized TiN/ZnS and TiN/ZnO thin films using X-ray absorption spectroscopy (XAS). The composite films were oxidized by post-deposition annealing (PDA) under various oxygen partial pressures (P(O2)). The results of the X-ray absorption near-edge structure (XANES) analyses showed that the S and N vaporized, and a zinc titanate (ZnTiO3)-like phase formed when annealed under the oxygen ambiance. An ab initio XANES simulation as well as the extended X-ray absorption fine structure (EXAFS) analysis further resolved the local structures of ZnTiO3-like phase into high symmetry structures such as ilmenite-like or perovskite-like local structure; for instance, the local structure of TiN/ZnS films annealed with P(O2) = 2 Torr could be described as a mixture of 50% ilmenite ZnTiO3 + 30% perovskite ZnTiO3 + 20% wurtzite ZnO local structures. The formation of ZnTiO3-like local structure is also subject to the temperature during the PDA or the choice of bottom layers (ZnS or ZnO). The temperature of the TiN/ZnS-to-ZnTiO3 local structural phase transformation, was estimated to be 500–600 °C at P(O2) = 2 Torr, and ZnO as bottom layer apparently expedited such local structural evolution by supplying oxygen to TiN.