A termination-insensitive and robust electron gas at the heterointerface of two complex oxides

The single-crystal SrTiO(3) (001) has two different surface terminations, TiO(2) and SrO. One most remarkable observation in previous studies is that only the heterointerfaces with TiO(2)-terminated SrTiO(3), which usually combines with polar oxides such as LaAlO(3), host an electron gas. Here we show that a robust electron gas can be generated between a non-polar oxide, CaHfO(3), and SrTiO(3) (001) with either termination. Unlike the well-known electron gas of LaAlO(3)/SrTiO(3), the present one of CaHfO(3)/SrTiO(3) essentially has no critical thickness of CaHfO(3), can survive a long-time oxygen annealing at high temperature, and its transport properties are stable under exposure to water and other polar solvents. By electrostatic gating through CaHfO(3), field-effect devices are demonstrated using CaHfO(3)/SrTiO(3) heterointerfaces with both terminations. These results show that the electron gas reported in the present study is unique and promising for applications in oxide electronics.