Thermodynamic criterion for searching high mobility two-dimensional electron gas at KTaO3 interface* *Project supported by the National Key R&D Program of China (Grant Nos. 2016YFA0300701, 2017YFA0206304, and 2018YFA0305704), the National Natural Science Foundation of China (Grant Nos. 11934016, 111921004, 51972335, and 11674378), and the Key Program of the Chinese Academy of Sciences (Grant Nos. XDB33030200 and QYZDY-SSW-SLH020).

Abstract

Two-dimensional electron gases (2DEGs) formed at the interface between two oxide insulators present a promising platform for the exploration of emergent phenomena. While most of the previous works focused on SrTiO3-based 2DEGs, here we took the amorphous-ABO3/KTaO3 system as the research object to study the relationship between the interface conductivity and the redox property of B-site metal in the amorphous film. The criterion of oxide–oxide interface redox reactions for the B-site metals, Zr, Al, Ti, Ta, and Nb in conductive interfaces was revealed: the formation heat of metal oxide, , is lower than –350 kJ/(mol O) and the work function of the metal Φ is in the range of 3.75 eV < Φ < 4.4 eV. Furthermore, we found that the smaller absolute value of and the larger value of Φ of the B-site metal would result in higher mobility of the two-dimensional electron gas that formed at the corresponding amorphous-ABO3/KTaO3 interface. This finding paves the way for the design of high-mobility all-oxide electronic devices.