Li Chen, Cao Yuyuan, Bai Yuhang, Li Aidong, Zhang Shantao, Wu Di
National Laboratory of Solid State Microstructures, Department of Materials Science and Engineering, College of Engineering and Applied Sciences, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China.
ACS Appl Mater Interfaces. 2015 May 20;7(19):10146-51. doi: 10.1021/am509113j. Epub 2015 May 5.
LaAlO3 ultrathin films, 10 unit cells in thickness, have been deposited epitaxially on TiO2-terminated (001) SrTiO3 substrates with various O2 pressures. Electromechanical response from the LaAlO3/SrTiO3 heterostructures is studied using combined piezoresponse force microscopy, electrostatic force microscopy, and scanning Kelvin probe microscopy. Oxygen vacancies are found to be responsible for the observed piezoelectric response but only for samples deposited with an oxygen pressure lower than 10(-5) mbar. However, ambient humidity is demonstrated to have a significant effect on the electromechanical response. The observations are discussed in terms of modulations on the intrinsic electrostriction in LAO/STO by an electric field induced by nonuniform distribution of either oxygen vacancies in the bulk or ionic adsorbates on the surface of LAO.
厚度为10个晶胞的LaAlO₃超薄膜已在具有不同氧气压力的TiO₂端接(001)SrTiO₃衬底上外延生长。使用压电响应力显微镜、静电力显微镜和扫描开尔文探针显微镜相结合的方法研究了LaAlO₃/SrTiO₃异质结构的机电响应。发现氧空位是观察到的压电响应的原因，但仅适用于在低于10⁻⁵毫巴的氧气压力下沉积的样品。然而，已证明环境湿度对机电响应有显著影响。根据由体相中氧空位或LAO表面上的离子吸附物的不均匀分布所诱导的电场对LAO/STO中固有电致伸缩的调制来讨论这些观察结果。
