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arXiv · 2306.05608

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

Ming Yang·Ariando Ariando·Caozheng Diao·James C Lee·Kaushik Jayaraman·Mansoor B A Jalil·Serban Smadici·Shengwei Zeng·Jun Zhou·Weilong Kong·Mark B. H. Breese·Sankar Dhar·Yuan Ping Feng·Peter Abbamonte·Thirumalai Venkatesan·Andrivo Rusydi
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Abstract

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

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Ming Yang, Ariando Ariando, Caozheng Diao, James C Lee, Kaushik Jayaraman, Mansoor B A Jalil, Serban Smadici, Shengwei Zeng, Jun Zhou, Weilong Kong, Mark B. H. Breese, Sankar Dhar, Yuan Ping Feng, Peter Abbamonte, Thirumalai Venkatesan, Andrivo Rusydi. 2023-06-09. Coexistence of surface oxygen vacancy and interface conducting states in LaAlO3/SrTiO3 revealed by low-angle resonant soft X-ray scattering. https://arxiv.org/abs/2306.05608

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