Experimentally, we found the percentage of low valence cations, the ionization energy of cations in film, and the band gap of substrates to be decisive for the formation of two-dimensional electron gas at the interface of amorphous/crystalline oxide (a-2DEG). Considering these findings, we inferred that the charge transfer from the film to the interface should be the main mechanism of a-2DEG formation. This charge transfer is induced by oxygen defects in film and can be eliminated by the electron-absorbing process of cations in the film. Based on this, we propose a simple dipole model that successfully explains the origin of a-2DEG, our experimental findings, and some important properties of a-2DEG.

No abstract

No abstract

A systematic study of the two-dimensional electron gas at LaAlO 3 /SrTiO 3 (110) interface reveals an anisotropy along two specific directions, [001] and 1 10 . The anisotropy becomes distinct for the interface prepared under high oxygen pressure with low carrier density. Angular dependence of magnetoresistance shows that the electron confinement is stronger along the 1 10 direction. Gate-tunable magnetoresistance reveals a clear in-plane anisotropy of the spin-orbit coupling, and the spin relaxation mechanism along both directions belongs to D'yakonov-Perel' (DP) scenario. Moreover, in-plane anisotropic superconductivity is observed for the sample with high carrier density, the superconducting transition temperature is lower but the upper critical field is higher along the 1 10 direction. This in-plane anisotropy could be ascribed to the anisotropic band structure along the two crystallographic directions.

Electrical transport property is closely related to the dimensionality of carriers' distribution. In this work, we succeed in tuning the carriers' distribution and the Rashba spin-orbit coupling at LaAlO 3 /SrTiO 3 interface by varying the oxygen pressure (c-P O2 ) adopted in crystalline LaAlO 3 growth. Measurements of the in-plane anisotropic magnetoresistance and the conducting-layer thickness indicate that the carriers' distribution changes from three to two dimensions with c-P O2 increasing, i.e. the electron confinement gets stronger. Importantly, by measuring the low-temperature out-of-plane magnetoresistance and analyzing the weak localization/weak anti-localization, we find that the strength of Rashba spin-orbit coupling can be enhanced by electron confinement. The electron confinement is a manifestation of breaking of spatial inversion symmetry. Therefore, our work reveals the intimate relationship between spatial inversion symmetry breaking and Rashba spin-orbit coupling at the LaAlO 3 / SrTiO 3 interface, and provides a new method to tune the Rashba spin-orbit coupling, which is valuable in the application of oxide-spintronics.