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Electronic and Structural Transitions of LaAlO₃ /SrTiO₃ Heterostructure Driven by Polar Field-Assisted Oxygen Vacancy Formation at the Surface.

ABSTRACT: The origin of 2D electron gas (2DEG) at LaAlO₃ /SrTiO₃ (LAO/STO) interfaces has remained highly controversial since its discovery. Various models are proposed, which include electronic reconstruction via surface-to-interface charge transfer and defect-mediated doping involving cation intermixing or oxygen vacancy (V_O ) formation. It is shown that the polar field-assisted V_O formation at the LAO/STO surface plays critical roles in the 2DEG formation and concurrent structural transition. Comprehensive scanning transmission electron microscopy analyses, in conjunction with density functional theory calculations, demonstrate that V_O forming at the LAO/STO surface above the critical thickness (t_c ) cancels the polar field by doping the interface with 2DEG. The antiferrodistortive (AFD) octahedral rotations in LAO, which are suppressed below the t_c , evolve with the formation of V_O above the t_c . The present study reveals that local symmetry breaking and shallow donor behavior of V_O induce the AFD rotations and relieve the electrical field by electron doping the oxide heterointerface.

SUBMITTER: Song K

PROVIDER: S-EPMC8292910 | biostudies-literature |

REPOSITORIES: biostudies-literature

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