Incipient ferroelectricity: A route towards bulk-terminated SrTiO3

TL;DR

This study presents a method to prepare and analyze the surface terminations of SrTiO3, revealing how strain-induced ferroelectric domains influence surface composition and defect distribution in this perovskite oxide.

Contribution

It introduces a simple procedure for creating bulk-terminated SrTiO3 surfaces and links ferroelectric domains to surface termination and defect patterns.

Findings

Controlled strain induces flat cleavage with distinct SrO and TiO2 domains.

Ferroelectric domains influence the distribution of surface terminations.

Point defects include Sr vacancies and adatoms with ~14% concentration.

Abstract

Perovskite oxides attract increasing attention due to their broad potential in many applications. Understanding their surfaces is challenging, though, because the ternary composition of the bulk allows for multiple stable surface terminations. We demonstrate a simple procedure for preparing the bulk-terminated (001) surface of SrTiO3, a prototypical cubic perovskite. Controlled application of strain on a SrTiO3 single crystal results in a flat cleavage with micrometer-size domains of SrO and TiO2. Distribution of these two terminations is dictated by ferroelectric domains induced by strain during the cleavage process. Atomically-resolved scanning tunneling microscopy/atomic force microscopy (STM/AFM) measurements reveal the presence of point defects in a well-defined concentration of (14+-2)%; Sr vacancies form at the SrO termination and complementary Sr adatoms appear at the TiO2 termination. These intrinsic defects are induced by the interplay between ferroelectricity, surface polarity, and surface charge.