Two-Dimensional Electron Gas with High Mobility Forming at BaO/SrTiO$_{3}$ Interface
Cheng Cao1,3†, Shengru Chen1,2†, Jun Deng1, Gang Li1,4, Qinghua Zhang1, Lin Gu1, Tian-Ping Ying1,4, Er-Jia Guo1,2,4*, Jian-Gang Guo1,4*, and Xiaolong Chen1,2,4*
1Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China 2School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 101408, China 3College of Materials Science and Opto-Electronic Technology, University of Chinese Academy of Sciences, Beijing 100049, China 4Songshan Lake Materials Laboratory, Dongguan 523808, China
Abstract：Two-dimensional electron gas (2DEG) with high electron mobility is highly desired to study the emergent properties and to enhance future device performance. Here we report the formation of 2DEG with high mobility at the interface between rock-salt BaO and perovskite SrTiO$_{3}$. The interface consists of the ionically compensated BaO$_{1-\delta}$ layer and the electronically compensated TiO$_{2}$ layer, which is demonstrated as a perfect interface without lattice mismatch. The so-formed interface features metallic conductivity with ultralow square resistance of $7.3 \times 10^{-4}\,\Omega /\square$ at 2 K and high residual resistance ratios $R_{\rm 300\,K}/R_{\rm 2\,K}$ up to 4200. The electron mobility reaches 69000 cm$^{2}$$\cdot$V$^{-1}$$\cdot$s$^{-1}$ at 2 K, leading to Shubnikov–de Haas oscillations of resistance. Density functional theory calculations reveal that the effective charge transfers from BaO to the Ti 3$d_{xy}$ orbital occur at the interface, leading to the conducting TiO$_{2}$ layer. Our work unravels that BaO can adapt itself by removing oxygen to minimize the lattice mismatch and to provide substantial carriers to SrTiO$_{3}$, which is the key to forming 2DEGs with high mobility at the interfaces.
. [J]. 中国物理快报, 2022, 39(4): 47301-047301.
Cheng Cao, Shengru Chen, Jun Deng, Gang Li, Qinghua Zhang, Lin Gu, Tian-Ping Ying, Er-Jia Guo, Jian-Gang Guo, and Xiaolong Chen. Two-Dimensional Electron Gas with High Mobility Forming at BaO/SrTiO$_{3}$ Interface. Chin. Phys. Lett., 2022, 39(4): 47301-047301.
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