Nature of electrons from oxygen vacancies and polar catastrophe at LaAlO₃/SrTiO₃ interfaces

Abstract

The relative significance of quantum conductivity correction and magnetic nature of electrons in understanding the intriguing low-temperature resistivity minimum and negative magnetoresistance (MR) of the two-dimensional electron gas at LaAlO 3 /SrTiO 3 interfaces has been a long outstanding issue since its discovery. Here we report a comparative magnetotransport study on amorphous and oxygen-annealed crystalline LaAlO 3 /SrTiO 3 heterostructures at a relatively high-temperature range, where the orbital scattering is largely suppressed by thermal fluctuations. Despite of a predominantly negative out-of-plane MR effect for both, the magnetotransport is isotropic for amorphous LaAlO 3 /SrTiO 3 while strongly anisotropic and well falls into a two-dimensional quantum correction frame for annealed crystalline LaAlO 3 /SrTiO 3 . These results clearly indicate that a large portion of electrons from oxygen vacancies are localized at low temperatures, serving as magnetic centers, while the electrons from the polar field are only weakly localized due to constructive interference between time-reversed electron paths in the clean limit and no signature of magnetic nature is visible.

Investigating the Electrical Transport and Photoresponse Properties of WSe2 and a Thermally Engineered SrTiO3-Based Heterojunction

“…5 In the wake of this finding, some other heterointerfaces of layered oxide structure, such as LaAlO 3 /STO, KTaO 3 /STO, LaAlO 3 /KTaO 3 , etc., were tested and also found to exhibit a high-mobility conducting interface. 6,7 This metallic interface was found to exhibit light-tunable current-transport properties, 8,9 Kondo effect, 10,11 the coexistence of superconductivity and ferromagnetism, 12 photomagnetoresistance (PMR), 13 and a large persistent photoconductivity effect. 8 Although this property of a conducting interface at layered oxides has been known for a long time, its integration with other functional materials for device applications has not been studied sufficiently.…”

“…A lot of methods have been employed to extract the maximum performance of electronic devices, such as functional interfaces with novel materials, strategic doping, molecular engineering, surface plasmon excitation, and defect engineering to control the absorption and trapping of photocarriers in PDs. − One such functional interface on complex oxide structures was first reported in 2004 by Ohtomo and Hwang, in which a conductive 2D electron gas was detected between LaAlO 3 and SrTiO 3 (STO) . In the wake of this finding, some other heterointerfaces of layered oxide structure, such as LaAlO 3 /STO, KTaO 3 /STO, LaAlO 3 /KTaO 3 , etc., were tested and also found to exhibit a high-mobility conducting interface. , This metallic interface was found to exhibit light-tunable current-transport properties, , Kondo effect, , the coexistence of superconductivity and ferromagnetism, photomagnetoresistance (PMR), and a large persistent photoconductivity effect . Although this property of a conducting interface at layered oxides has been known for a long time, its integration with other functional materials for device applications has not been studied sufficiently.…”

The Role of Oxygen Transfer in Oxide Heterostructures on Functional Properties

“…Although conduction mechanisms based on polar catastrophe and OV in LAO/STO systems are well studied, [5,15,20,21,32] the origin of OV is less clear. [6,8,10,14,19,20,33] The generation of OV is often believed to be due to the low oxygen growth pressure at high growth temperatures.…”