Thermodynamic criterion for searching high mobility two-dimensional electron gas at KTaO₃ interface

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 SrTiO_3-based 2DEGs, here we took the amorphous-ABO_3/KTaO_3 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, \Delta H_\rm f^\rm o, is lower than -350 kJ/(mol O) and the work function of the metal \varPhi is in the range of 3.75 eV <\varPhi <4.4 eV. Furthermore, we found that the smaller absolute value of \Delta H_\rm f^\rm o and the larger value of \varPhi of the B-site metal would result in higher mobility of the two-dimensional electron gas that formed at the corresponding amorphous-ABO_3/KTaO_3 interface. This finding paves the way for the design of high-mobility all-oxide electronic devices.