Multifunctional control of oxide interface via surface-oxygen-vacancy engineering

Interfacial properties of oxide heterostructures, such as LaAlO3 (LAO)/SrTiO3 (STO), are closely related to the surface physicochemical states, offering unprecedented avenues for device tuning. Herein, we demonstrate that surface oxygen vacancy engineering through amorphous-LAO capping layer enables multifunctional control of interfacial conductivity, Kondo physics, and Rashba spin-orbit coupling at LAO/STO (001). X-ray photoelectron spectroscopy and electrical transport measurements reveal that the formation of oxygen vacancies at the LAO surface triggers charge transfer and insulator-to-metal transition of LAO/STO, with its carrier density increasing from 0.55 × 1013 to 1.08 × 1013 cm-2 as the amorphous-LAO thickness grows. The low-temperature resistance upturn exhibits Kondo effect characteristics, with Kondo temperature rising from 10.88 to 35.11 K concomitantly, accompanied by a two-orders-of-magnitude reduction in Kondo resistance, reflecting the transition of Kondo scattering center from Cr to Ti. Magnetotransport further reveals the enhancement of Rashba spin-orbital coupling with Rashba spin splitting energy Eso increasing from 2.54 to 4.07 meV and signature of Elliott-Yafet spin relaxation mechanism (spin-orbital relaxation time τso ∝ elastic scattering time τel), suggesting Cr ions as possible spin-orbit scattering impurities.