Anisotropic magneto-transport properties of electron gases at SrTiO3 (111) and (110) surfaces

Electron gases at the surfaces of insulating (111)- and (110)-oriented SrTiO3 (STO) single crystals have been created using Ar+-irradiation and their magneto-transport properties are characterized. Fully metallic behaviors with sheet carrier density of ∼1014 cm−2 and low-temperature-mobilities as large as 8600 cm2 V−1 s−1 are obtained. Intrinsic in-plane anisotropic magnetoresistance (AMR) has been obtained by applying current along different crystal axes to subtract the Lorentz force effect. The results yield nearly 6-fold and 2-fold components for the (111)-and (110)-surfaces. A symmetry breaking in AMR for the (111)-surfaces with ordering temperature TO ∼ 30 K is also observed. In contrast, the out-of-plane AMR does not show anisotropy associated with crystal axes, suggesting a two-dimensional nature of the effect. Our results demonstrate that electron gases at (111)- and (110)-oriented STO surfaces are a promising playground for both fundamental research and all-oxide device applications.