Quasi-two-dimensional electron gas at γ-Al2O3/SrTiO3 heterointerfaces fabricated by spin coating method

Abstract

Complex oxide heterointerfaces with the two-dimensional electron gas have drawn a lot of attention due to their emerging properties. However, most of them are prepared using the method with relatively high energy particles, which would inevitably lead to some defects. Here, a key challenge in the quasi-two-dimensional electron gas at spinel-type Al2O3/SrTiO3 heterointerfaces using a spin coating method is addressed. The grown Al2O3 films have the atomic-scale smooth surface and the thickness is about 70 nm. The γ-Al2O3 layer with a thickness of about 3 nm in proximity to SrTiO3 and the amorphous Al2O3 layer on the top of γ-Al2O3 are observed for the heterointerface annealed at 800 °C. The heterointerfaces at annealed temperatures above 750 °C exhibit a metallic behavior, which is attributed to the dominant layer of γ-Al2O3. The sheet carrier density is about 3.1 × 1015 cm−2 and the Hall mobility is 4924.4 cm2 V−1 s−1 at 15 K at the heterointerface annealed at 800 °C. Our work provides a low-cost way for the large-scale and large-area production of two-dimensional electron gas at high-quality oxide interfaces.