Interfacial control of SrTiO3/Si(001) epitaxy and its effect on physical and optical properties

Abstract

The direct heteroepitaxy of strontium titanate (SrTiO3, STO) oxide on Si(0 0 1) substrate is an important step to integrate other functional perovskite oxides onto large scale wafers. In this study, we focused on the SrO interfacial layer in function of molecular oxygen gas exposure amount prior to the STO growth. The various formed interfaces showed large impact on the subsequent STO growth, including crystal quality and stoichiometry. The chemical binding states showed that the formation of thick SiOx interfacial layer was strongly correlated with the molecular oxygen exposure amount. More interestingly, the film stoichiometry is also strongly affected with overexposure, which resulted in optical properties degradation of the STO films. The STO optical constants, extracted from the spectroscopic ellipsometry (SE), exhibit obvious differences between crystalline and amorphous samples. Finally, post-deposition annealing was used to reduce the optical extinction, which is of primary importance for photonic applications.