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

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• 作者：Luc铆a Aballe ; Sonia Matencio ; Michael Foerster ; Esther Barrena ; Florencio S谩nchez ; Josep Fontcuberta ; Carmen Ocal
• 刊名：Chemistry of Materials
• 出版年：2015
• 出版时间：September 22, 2015
• 年：2015
• 卷：27
• 期：18
• 页码：6198-6204
• 全文大小：397K
• ISSN：1520-5002

文摘

The (001)SrTiO₃ crystal surface can be engineered to display a self-organized pattern of well-separated and nearly pure single-terminated SrO and TiO₂ 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 TiO₂) is determined to be 桅(SrO) < 桅(TiO₂), in agreement with theoretical predictions, although the measured difference 螖桅 鈮?100 meV is definitely below calculations for ideally pure single-terminated SrO and TiO₂ surfaces. These relative values are maintained if samples are annealed in UHV up to 200 掳C. Annealing in UHV at higher temperature (400 掳C) preserves the surface morphology of self-assembled TiO₂ 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)SrTiO₃ surfaces, widely used in oxide thin film growth, can largely vary before growth starts in a manner strongly dependent on temperature and pressure conditions.