Since the discovery of two-dimensional electron gas at the LaAlO3/SrTiO3 interface, its intriguing physical properties have garnered significant interests for device applications. Yet, understanding its response to electrical stimuli remains incomplete. Our in-situ transmission electron microscopy analysis of a LaAlO3/SrTiO3 two-dimensional electron gas device under electrical bias reveals key insights. Inline electron holography visualized the field-induced modulation of two-dimensional electron gas at the interface, while electron energy loss spectroscopy showed negligible electromigration of oxygen vacancies. Instead, atom-resolved imaging indicated that electric fields trigger polar distortion in the LaAlO3 layer, affecting two-dimensional electron gas modulation. This study refutes the previously hypothesized role of oxygen vacancies, underscoring the lattice flexibility of LaAlO3 and its varied polar distortions under electric fields as central to two-dimensional electron gas dynamics. These findings open pathways for advanced oxide nanoelectronics, exploiting the interplay of polar and nonpolar distortions in LaAlO3.
This work was supported by the Samsung Research Funding & Incubation Center of Samsung Electronics under Project Number SRFC-MA1702-01 (S.H.O. and J.L.) and partly by the National Research Foundation of Korea (NRF) funded by the Korea government (MSIT) (No. NRF-2020R1A2C2101735), Creative Materials Discovery Program (NRF-2019M3D1A1078296), and, the KENTECH Research Grant (KRG2022-01-019) (S.H.O.). The first-principle calculations were performed using the facilities of the Joint Supercomputer Center of the Russian Academy of Sciences (JSCC RAS). J.L. acknowledges the support of an NRF grant funded by the Korean government (NRF-2018R1A2B6004394). The TEM work at Sungkyunkwan University (SKKU) was supported by the Advanced Facility Center for Quantum Technology and the TEM work at the Korea Institute of Energy Technology (KENTECH) was supported by the Center for Shared Research Facilities (S.H.O.). This research is funded by the Gordon and Betty Moore Foundation\\u2019s EPiQS Initiative, grant GBMF9065 to C.B.E. and Vannevar Bush Faculty Fellowship (N00014-20-1-2844 (C.-B.E.)). Transport measurement at the University of Wisconsin\\u2013Madison was supported by the US Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences (BES), under award number DE-FG02-06ER46327 (C.-B.E.).
