Atomic Scale Studies of SrTiO₃/ n NdTiO₃ /SrTiO₃(001) Heterostructures by Synchrotron X-ray Methods

Epitaxial thin films have been widely used as model systems in many studies due to their well-ordered structures, smooth surfaces, and single orientations. ‪Probing of their atomic structures and correlating such structures with the corresponding physical behaviors are very important to understand the mechanisms of several critical phenomena such as 2-dimensional (2D) electron gases, ion intercalation for energy storage and surface restructuring in (electro)chemical reactions. In this talk, I will illustrate how we utilized several synchrotron techniques (surface X-ray scattering, coherent Bragg rod analysis, etc.) to obtain atomic-scale insights of structure-property relation for heterostructured thin films. In particular, for SrTiO₃/ n NdTiO₃ /SrTiO₃(001) heterojunction, by combining quantitative synchrotron X-ray-based interface structure determination with ab initio modeling, we demonstrate that Nd vacancy formation and the resulting formation of Nd adatoms, stabilized by oxygen scavengers at the growth front, can quantitatively account for the decreased carrier concentration at the such heterojunction for n = 1 unit cell. Our study yields insight into growth mechanisms and the effect of transient species and defects on the electronic properties of oxide heterojunctions and how transient electron scavengers can be utilized to control the carrier concentration at polar/non-polar perovskite interfaces.