Surface properties of atomically flat poly-crystalline SrTiO3

TL;DR

This study develops a method to produce atomically flat single- and poly-crystalline SrTiO3 surfaces, enabling precise comparison of their properties and advancing understanding of grain boundary effects in transition metal oxides.

Contribution

The paper introduces a fabrication approach for atomically flat poly-crystalline SrTiO3 substrates, facilitating detailed studies of grain boundary phenomena in TMOs.

Findings

Successfully prepared atomically flat poly-crystalline STO surfaces.

Optimized annealing conditions for different STO surface orientations.

Enables comparative studies of single- and poly-crystalline TMO properties.

Abstract

Comparison between single- and the poly-crystalline structures provides essential information on the role of long-range translational symmetry and grain boundaries. In particular, by comparing single- and poly-crystalline transition metal oxides (TMOs), one can study intriguing physical phenomena such as electronic and ionic conduction at the grain boundaries, phonon propagation, and various domain properties. In order to make an accurate comparison, however, both single- and poly-crystalline samples should have the same quality, e.g., stoichiometry, crystallinity, thickness, etc. Here, by studying the surface properties of atomically flat poly-crystalline SrTiO3 (STO), we propose an approach to simultaneously fabricate both single- and poly-crystalline epitaxial TMO thin films on STO substrates. In order to grow TMOs epitaxially with atomic precision, an atomically flat, single-terminated surface of the substrate is a prerequisite. We first examined (100), (110), and (111) oriented single-crystalline STO surfaces, which required different annealing conditions to achieve atomically flat surfaces, depending on the surface energy. A poly-crystalline STO surface was then prepared at the optimum condition for which all the domains with different crystallographic orientations could be successfully flattened. Based on our atomically flat poly-crystalline STO substrates, we envision expansion of the studies regarding theTMOdomains and grain boundaries.