Luo Dianbing, Chen Yunhai, Wang Yifei, Cao Xinyu, Aung Phyo, Jin Kexin, Wang Shuanhu
Shaanxi Key Laboratory of Condensed Matter Structures and Properties and MOE Key Laboratory of Materials Physics and Chemistry under Extraordinary Conditions, School of Physical Science and Technology, Northwestern Polytechnical University, Xi'an 710072, People's Republic of China.
J Phys Condens Matter. 2023 Nov 23;36(9). doi: 10.1088/1361-648X/ad0d29.
Oxygen vacancy is one of the original mechanisms of the two-dimensional electron gas (2DEG) at the LaAlO(LAO) and SrTiO(STO) heterogeneous interface, and it has an important impact on the electrical properties of LAO/STO heterojunction. In this work, the LAO thin films were grown on the STO substrates by pulsed laser deposition, and the electrical transport behavior of the LAO/STO interface at high temperature and high vacuum were systematically studied. It was found that at high temperature and high vacuum, the oxygen vacancies-rich LAO/STO heterojunction would undergo a metal-insulator transition, and return to metal conductivity when the temperature is further increased. At this time, the conduction mechanism of the sample is drift mode and the thermal activation energy is 0.87 eV. While during the temperature decreasing, the conduction mechanism would transfer to hopping conduction with the thermal activation energy of 0.014 eV and the resistance would increase dramatically and present a completely insulated state. However, when the oxygen vacancies-rich sample is exposed to air, the resistance would gradually decrease and recover.
氧空位是LaAlO（LAO）和SrTiO（STO）异质界面处二维电子气（2DEG）的原始机制之一，它对LAO/STO异质结的电学性质有重要影响。在这项工作中，通过脉冲激光沉积在STO衬底上生长LAO薄膜，并系统研究了高温高真空下LAO/STO界面的电输运行为。研究发现，在高温高真空下，富含氧空位的LAO/STO异质结会发生金属-绝缘体转变，当温度进一步升高时又恢复到金属导电状态。此时，样品的传导机制为漂移模式，热激活能为0.87 eV。而在温度降低过程中，传导机制会转变为跳跃传导，热激活能为0.014 eV，电阻会急剧增加并呈现完全绝缘状态。然而，当富含氧空位的样品暴露在空气中时，电阻会逐渐降低并恢复。
