Nanoscale interplay of native point defects near Sr-deficient SrxTiO3/SrTiO3 interfaces

Abstract

SrTiO3 has many applications involving interfaces with other materials, but defects that affect the properties of SrTiO3 films can also play a significant role at its heterointerfaces and even at junctions with nonstoichiometric SrTiO3. Depth-resolved cathodoluminescence spectroscopy (DRCLS) combined with systematic cation Sr content reduction in SrxTiO3 ultrathin films grown on SrTiO3 showed an interplay of native point defects and electronic structure within the Sr-deficient film and how interplay extends tens of nanometers into the substrate below. Understanding how defects form and affect interface electronic structure during epitaxial growth is central to improving complex oxide devices. Controlling the balance of oxygen vacancy defects with strontium vacancies and other acceptor-like defects can improve control over free carrier densities. Likewise, control over nanoscale defect charge distributions can advance new device features such as two-dimensional hole gases and the performance of existing devices such as ferroelectric tunnel junctions. This study shows how DRCLS directly measures the relative densities and spatial distributions of multiple native defects within and extending away from nanoscale SrxTiO3/SrTiO3 junctions and how their interplay varies with controlled epitaxial growth. In turn, these growth-dependent defect variations can help guide SrTiO3 epitaxial growth with other complex oxides.