Coexistence of surface oxygen vacancy and interface conducting states in LaAlO3/SrTiO3 revealed by grazing-angle resonant soft x-ray scattering

Oxide heterostructures have shown rich physics phenomena, particularly in the conjunction of exotic insulator–metal transition (IMT) at interface between polar insulator LaAlO3 and non-polar SrTiO3 (LaAlO3/SrTiO3). The polarization catastrophe model has suggested an electronic reconstruction, yielding to metallicity both surface. Another scenario is occurrence surface oxygen vacancy (surface-Ov), which predicted surface-to-interface charge transfer, metallic but insulating To clarify origin IMT, one should probe surface-Ov associated structures buried simultaneously. Here, using grazing-angle resonant soft x-ray scattering (GA-RSXS) supported with first-principles calculations, we reveal co-existence state conducting only LaAlO3/SrTiO3 (001) films. Interestingly, are absent for film. As a function Ov density, while responsible spatial distribution found from two-dimensional-like three-dimensional-like conductivity accompanied by spectral weight revealing importance correlation. Our results show determining properties provide new strategy utilizing GA-RSXS directly complex oxide heterostructures.