High-Quality Heteroepitaxial Growth of Thin Films of the Perovskite Oxynitride CaTaO2N: Importance of Interfacial Symmetry Matching between Films and Substrates
High-Quality Heteroepitaxial Growth of Thin Films of the Perovskite Oxynitride CaTaO2N: Importance of Interfacial Symmetry Matching between Films and Substrates
复制标题
DOI：
10.1021/acsomega.0c01601
复制
发表时间：
2020-05
期刊：
影响因子：
4.1
通讯作者：
Takuto Wakasugi;Y. Hirose;S. Nakao;Y. Sugisawa;D. Sekiba;T. Hasegawa
中科院分区：
文献类型：
--
作者：
Takuto Wakasugi;Y. Hirose;S. Nakao;Y. Sugisawa;D. Sekiba;T. Hasegawa
钙钛矿氧氮化物在可见光驱动下的光催化活性和新的电子功能方面进行了研究。氮氧化合物固有的物理和/或电化学性质的评估需要单晶薄膜的外延生长。然而，与钙钛矿氧化物的研究进展相比，钙钛矿氧化氮的异质外延尚未成熟。本文报道了利用反应性射频磁控溅射在SrTiO3衬底上生长具有（100）pc、（110）pc和（111）pc晶体表面取向的CaTaO2N薄膜（下标pc表示伪晶胞），并对结晶度和表面形貌进行了研究。无论表面取向如何，化学测量的CaTaO2N外延薄膜在SrTiO3衬底上均匀生长，在薄膜厚度约为20 nm的情况下，呈现出清晰的台阶和台阶表面。（110）pc取向的薄膜也比（100）pc取向和（111）pc取向的样品具有更高的结晶性。这种结晶度与表面取向之间的关系归因于正交CaTaO2N和立方SrTiO3之间的对称性失配所导致的不相等的面内旋转畴的数量。在晶格和对称匹配的正交DyScO3衬底上生长的CaTaO2N薄膜显示出显著的结晶度和清晰的台阶和台阶表面，即使薄膜厚（~ 190 nm）。这些结果有望为高质量氧化氮钙钛矿薄膜的异质外延生长提供帮助。
Perovskite oxynitrides have been studied with regard to their visible light-driven photocatalytic activity and novel electronic functionalities. The assessment of the intrinsic physical and/or electrochemical properties of oxynitrides requires the epitaxial growth of single-crystalline films. However, the heteroepitaxy of perovskite oxynitrides has not yet matured compared to the progress realized in work with perovskite oxides. Herein, we report the heteroepitaxial growth of CaTaO2N thin films with (100)pc, (110)pc, and (111)pc crystallographic surface orientations (where the subscript pc denotes a pseudocubic cell) on SrTiO3 substrates using reactive radio frequency magnetron sputtering, along with investigations of crystallinity and surface morphology. Irrespective of surface orientation, stoichiometric CaTaO2N epitaxial thin films were grown coherently on SrTiO3 substrates and showed clear step and terrace surfaces in the case of low values of film thickness of approximately 20 nm. A (110)pc-oriented film was also more highly crystalline than (100)pc- and (111)pc-oriented specimens. This relationship between crystallinity and surface orientation is ascribed to the number of inequivalent in-plane rotational domains, which stems from the symmetry mismatch between the orthorhombic CaTaO2N and cubic SrTiO3. A CaTaO2N thin film grown on a lattice- and symmetry-matched orthorhombic DyScO3 substrate exhibited a significant crystallinity and a clear step and terrace surface even though the film was thick (∼190 nm). These results are expected to assist in developing the heteroepitaxial growth of high-quality perovskite oxynitride thin films.