Work

Instability and Surface Potential Modulation of Self-Patterned (001)SrTiO3 Surfaces

Year: 2015

Type: article

Abstract: The (001)SrTiO 3 crystal surface can be engineered to display a self-organized pattern of well-separated and nearly pure single-terminated SrO and TiO 2 regions by high temperature annealing in oxidizing atmosphere. By using surface sensitive techniques we have obtained evidence of such a surface chemical self-structuration in as-prepared crystals and unambiguously identified the local composition. The contact surface potential at regions initially consisting of majority single terminations (SrO and TiO 2 ) is determined to be Φ(SrO) < Φ(TiO 2 ), in agreement with theoretical predictions, although the measured difference ΔΦ ≤ 100 meV is definitely below calculations for ideally pure single-terminated SrO and TiO 2 surfaces. These relative values are maintained if samples are annealed in UHV up to 200 °C. Annealing in UHV at higher temperature (400 °C) preserves the surface morphology of self-assembled TiO 2 and SrO rich regions, although a non-negligible chemical intermixing is observed. The most dramatic consequence is that the surface potential contrast is reversed. It thus follows that electronic and chemical properties of (001)SrTiO 3 surfaces, widely used in oxide thin film growth, can largely vary before growth starts in a manner strongly dependent on temperature and pressure conditions.

Source: Chemistry of Materials

DOI: 10.1021/acs.chemmater.5b00661