Zhou Zizhen, Chu Dewei, Cazorla Claudio
School of Materials Science and Engineering, UNSW Australia, Sydney, NSW 2052 Australia.
Departament de Física, Universitat Politècnica de Catalunya, Campus Nord B4-B5, 08034 Barcelona, Spain.
Sci Rep. 2021 Jun 1;11(1):11499. doi: 10.1038/s41598-021-91018-4.
Epitaxially grown [Formula: see text] (STO) thin films are material enablers for a number of critical energy-conversion and information-storage technologies like electrochemical electrode coatings, solid oxide fuel cells and random access memories. Oxygen vacancies ([Formula: see text]), on the other hand, are key defects to understand and tailor many of the unique functionalities realized in oxide perovskite thin films. Here, we present a comprehensive and technically sound ab initio description of [Formula: see text] in epitaxially strained (001) STO thin films. The novelty of our first-principles study lies in the incorporation of lattice thermal excitations on the formation energy and diffusion properties of [Formula: see text] over wide epitaxial strain conditions ([Formula: see text]%). We found that thermal lattice excitations are necessary to obtain a satisfactory agreement between first-principles calculations and the available experimental data for the formation energy of [Formula: see text]. Furthermore, it is shown that thermal lattice excitations noticeably affect the energy barriers for oxygen ion diffusion, which strongly depend on [Formula: see text] and are significantly reduced (increased) under tensile (compressive) strain. The present work demonstrates that for a realistic theoretical description of oxygen vacancies in STO thin films is necessary to consider lattice thermal excitations, thus going beyond standard zero-temperature ab initio approaches.
外延生长的钐钛酸镧（STO）薄膜是多种关键能量转换和信息存储技术的材料支撑，如电化学电极涂层、固体氧化物燃料电池和随机存取存储器。另一方面，氧空位是理解和定制氧化物钙钛矿薄膜中许多独特功能的关键缺陷。在此，我们对外延应变（001）STO薄膜中的氧空位进行了全面且技术可靠的从头算描述。我们第一性原理研究的新颖之处在于，在较宽的外延应变条件（-2%至2%）下，将晶格热激发纳入氧空位的形成能和扩散特性研究中。我们发现，对于氧空位形成能的第一性原理计算与现有实验数据之间要达成令人满意的一致性，晶格热激发是必要的。此外，研究表明晶格热激发显著影响氧离子扩散的能垒，该能垒强烈依赖于应变，并且在拉伸（压缩）应变下会显著降低（增加）。本工作表明，对于STO薄膜中氧空位进行现实的理论描述，有必要考虑晶格热激发，从而超越标准的零温度从头算方法。
