High Mobility Two-Dimensional Electron Gases at Non-Polar Interfaces
Ping-Chun Wu1*, Ying-Hao Chu1,2,3
1Department of Materials Sciences and Engineering, National Chiao Tung University, Hsinchu, Taiwan
2Department of Electrophysics, National Chiao Tung University, Hsinchu, Taiwan
3Department of Material and Chemical Research Laboratories, Industrial Technology Research Institute, Hsinchu, Taiwan
* Presenter:Ping-Chun Wu, email:bjwu.mse03g@nctu.edu.tw
The discovery of two-dimensional electron gases (2DEGs) at the interface of LaAlO3/SrTiO3 (LAO/STO) heterostructure has advanced the opportunity for oxide electronics. So far, the creation of 2DEGs at oxide interface still remains a huge debate. There are three main mechanisms that have been proposed: electronic reconstruction due to the polar discontinuity, accumulation of oxygen vacancy, and intermixing at the interface. These theories have earned wide recognition but arguments still remain unsettled. In this work, we create 2DEGs at non-polar interfaces by depositing strontium zirconate (SrZrO3), calcium titante (CaTiO3) and STO on STO substrate. The electron mobilities of the samples are all over 20,000 cm2V-1s-1 at 4 K. The XRD reciprocal space mapping has demonstrated that the films are under biaxial strain. X-ray photoemission spectroscopy is adopted to reveal the band structure at the interface. Scanning transmission electron microscopy and electron energy-loss spectroscopy are used to evidence the origin of the 2DEGs. This work has excluded the claim of electronic reconstruction from polar discontinuity by creating 2DEGs at non-polar interface. Further, the notion of intermixing is also inconsistent since 2DEGs have been observed at homoepitaxial STO/STO interface. This work advanced the pathway to explore the origin of 2DEGs at oxide interfaces.

Keywords: two dimensional electron gas, interface