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 MgAl2O4 and perovskite SrTiO3. Transport measurements, electron microscopy imaging, and first-principles calculations reveal that the interfacial 2DEG is closely related to the symmetry breaking at the MgAl2O4/SrTiO3 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 LaAlO3/SrTiO3 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.
|Original language||English (US)|
|Journal||ACS Applied Materials & Interfaces|
|State||Published - Aug 25 2020|
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: This work was performed by the Clean Combustion Research Center with funding from King Abdullah University of Science and Technology (KAUST), University of California, San Diego and Saudi Aramco under the FUELCOM program. Research reported in this publication was also supported by competitive research funding from KAUST.