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.

Heterointerfaces between two insulators play a central role in the study of oxide electronics owing to a spectrum of emergent properties. Manipulating transport of the interface by light can result in significant modulation of the ground state and excite localized states. However, their dynamics and mechanisms of photogenerated carries remain unclear. Here, this study presents the dynamics of carrier density and mobility under and after light illumination by Hall effect over time. It is discovered that the density and mobility after light illumination obey a stretched exponential expression, further indicating that the variation of mobility caused by the electron-electron scattering plays an important role in the recovery process in addition to the reduction of carrier density. Meanwhile, a non-linear Hall resistance at the LaAlO3/SrTiO3 interface under the illumination of a 360 nm laser at low temperature is observed. Furthermore, the gating effect can tune the recovery process after light illumination and induce a disappearance of non-linear Hall resistance. The results provide the experimental support for detailed mechanisms of the nonequilibrium process and developing of all-oxide electronic devices based on heterointerfaces.

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A magnetic conductive outer layer at insulating rutile TiO 2 crystals is obtained by high-temperature annealing at low oxygen pressure. The conductivity here is closely dependent on the annealing temperature and time and originates from oxygen vacancies, which has been verified by the observed mixed valence of Ti 3þ/4þ . The most striking observation is the occurrence of ferromagnetism demonstrated by ferromagnetic hysteresis and anomalous Hall effect. The ferromagnetic hysteresis is weakly temperature dependent, which implies a defect-induced ferromagnetism. The anomalous Hall effect provides transport evidence for the existence of a long-range ferromagnetic order. The present work presents a prototypical case of designing surface physics from the interplay of multiple factors.

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