Ding Junfeng, Cheng Jianli, Dogan Fatih, Li Yangyang, Lin Weinan, Yao Yingbang, Manchon Aurelien, Yang Kesong, Wu Tom
Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei 230031, People's Republic of China.
Department of NanoEngineering, University of California, San Diego, La Jolla, California 92093-0448, United States.
ACS Appl Mater Interfaces. 2020 Sep 23;12(38):42982-42991. doi: 10.1021/acsami.0c13337. Epub 2020 Sep 10.
Two-dimensional electron gas (2DEG) at the interface between two insulating perovskite oxides has attracted much interest for both fundamental physics and potential applications. Here, we report the discovery of a new 2DEG formed at the interface between spinel MgAlO and perovskite SrTiO. Transport measurements, electron microscopy imaging, and first-principles calculations reveal that the interfacial 2DEG is closely related to the symmetry breaking at the MgAlO/SrTiO interface. The critical film thickness for the insulator-to-metal transition is approximately 32 Å, which is twice as thick as that reported on the widely studied LaAlO/SrTiO system. Scanning transmission electron microscopy imaging indicates the formation of interfacial Ti-Al antisite defects with a thickness of ∼4 Å. First-principles density functional theory calculations indicate that the coexistence of the antisite defects and surface oxygen vacancies may explain the formation of interfacial 2DEG as well as the observed critical film thickness. The discovery of 2DEG at the spinel/perovskite interface introduces a new material platform for designing oxide interfaces with desired characteristics.
两种绝缘钙钛矿氧化物界面处的二维电子气（2DEG）因其在基础物理学和潜在应用方面的价值而备受关注。在此，我们报告了在尖晶石MgAlO与钙钛矿SrTiO界面处形成新型二维电子气的发现。输运测量、电子显微镜成像以及第一性原理计算表明，界面二维电子气与MgAlO/SrTiO界面处的对称性破缺密切相关。绝缘体到金属转变的临界薄膜厚度约为32 Å，是广泛研究的LaAlO/SrTiO体系报道厚度的两倍。扫描透射电子显微镜成像表明形成了厚度约为4 Å的界面Ti-Al反位缺陷。第一性原理密度泛函理论计算表明，反位缺陷与表面氧空位的共存可能解释了界面二维电子气的形成以及观察到的临界薄膜厚度。尖晶石/钙钛矿界面二维电子气的发现为设计具有所需特性的氧化物界面引入了一个新的材料平台。
