In-situ Investigation of the Early Stage of TiO2 epitaxy on (001) SrTiO3

TL;DR

This study investigates the initial growth stages of TiO2 on SrTiO3, revealing a pseudomorphic Sr-Ti-O layer formation that influences phase stabilization, using in-situ techniques to analyze epitaxial film development.

Contribution

It provides new insights into the early epitaxial growth mechanisms of TiO2 on SrTiO3, highlighting the role of Sr migration and interface energetics.

Findings

Formation of a 2-4 nm Sr-Ti-O intermediate layer precedes anatase TiO2 growth.

Long-range Sr migration from substrate to film is crucial for phase stabilization.

Results expand the understanding of the Sr-Ti-O phase diagram under epitaxial strain.

Abstract

We report on a systematic study of the growth of epitaxial TiO2 films deposited by pulsed laser deposition on Ti-terminated (001) SrTiO3 single crystals. By using in-situ reflection high energy electron diffraction, low energy electron diffraction, x-ray photoemission spectroscopy and scanning probe microscopy, we show that the stabilization of the anatase (001) phase is preceded by the growth of a pseudomorphic Sr-Ti-O intermediate layer, with a thickness between 2 and 4 nm. The data demonstrate that the formation of this phase is related to the activation of long range Sr migration from the substrate to the film. The role of interface Gibbs energy minimization, as a driving force for Sr diffusion, is discussed. Our results enrich the phase diagram of the Sr-Ti-O system under epitaxial strain opening the roudeficient SrTiO phase.