Surface termination effect of SrTiO3 substrate on ultrathin SrRuO3

TL;DR

This study reveals how the surface termination of SrTiO3 substrates influences the growth and properties of ultrathin SrRuO3 films, emphasizing the need for single termination substrates to achieve high-quality epitaxial heterostructures.

Contribution

It provides atomic-scale insights into how different step propagations on SrTiO3 substrates affect the growth and properties of ultrathin SrRuO3 films, highlighting the importance of substrate termination control.

Findings

Type-II [0-11] steps cause lateral discontinuity in SrRuO3

Mixed surface terminations induce defects affecting film properties

Single termination substrates improve film quality

Abstract

A uniform one-unit-cell-high step on the SrTiO3 substrate is a prerequisite for growing high-quality epitaxial oxide heterostructures. However, it is inevitable that defects induced by mixed substrate surface termination exist at the interface, significantly impacting the properties of ultrathin films. In this study, we microscopically identify the origin for the lateral inhomogeneity in the growth of ultrathin SrRuO3 films due to the step effects of SrTiO3(001). By using atomic-resolved scanning transmission electron microscopy, we observe two distinct types of step propagation along the [011] and [0-11]crystallographic direction in SrTiO3-SrRuO3 heterostructures, respectively. In particular, the type-II [0-11] step results in lateral discontinuity of monolayer SrRuO3 and originates from the SrO-terminated regions along the TiO2-terminated step edge. Such an induced lateral discontinuity should be responsible for the distinct electronic and magnetic properties of monolayer SrRuO3. Our findings underscore the critical importance of using single termination STO substrate to achieve high-quality termination selective films and to unveil the intrinsic properties of epitaxial films in the atomic limit.