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Resolving Interfacial Charge Transfer in Titanate Superlattices using Resonant X-Ray Reflectometry



Ryan F. Need, P. B. Marshall, E. Weschke, Alexander J. Grutter, Dustin Allen Gilbert, E. Arenholz, P. Shafer, S. Stemmer, Stephen D. Wilson


Oxide interfaces, where strong electron-electron correlations lead to emergent phase behavior, have been the subject of intense study in recent years. However, the buried nature of heterointerfaces often makes them challenging to probe directly. Addressing this challenge requires a technique capable of measuring the local electronic, orbital, and magnetic structure with high-resolution depth dependence. Recently, resonant X-ray reflectometry (RXR) has emerged as an ideal candidate for such studies. Here, we have used linearly-polarized RXR to measure valence depth profiles for SmTiO3 (SmTO)/SrTiO3 (STO) heterostructures and characterize charge transfer at their buried interfaces. An electronic discontinuity at the polar-nonpolar SmTO/STO interface leads to approximately half an electron per areal unit cell transferred from the interfacial SmO layer into the neighboring STO quantum well. We observe this charge transfer as a suppression of the t2g absorption peak in refinements from superlattice samples with STO wells varying in thickness from 5 SrO planes down to a single, atomically thin SrO plane. Our results hihglight the extreme sensitivity of RXR to electronic reconstruction and charge transfer at the atomic scale, even when the interfaces are buried far below a surface contaminated by oxidation.
Physical Review Materials


X-ray reflectometry, resonant absorption, Mott insulators, complex oxide, charge transfer, local electronic structure


Need, R. , , P. , Weschke, E. , Grutter, A. , , D. , Arenholz, E. , Shafer, P. , Stemmer, S. and , S. (2018), Resolving Interfacial Charge Transfer in Titanate Superlattices using Resonant X-Ray Reflectometry, Physical Review Materials, [online], (Accessed June 13, 2024)


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Created September 6, 2018, Updated February 25, 2020