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Transition metal oxide heterostructures are interesting due to the distinctly different properties that can arise from their interfaces, such as superconductivity, high catalytic activity, and magnetism. Oxygen point defects can play an important role at these interfaces in inducing potentially novel properties. The design of oxide heterostructures in which the oxygen defects are manipulated to attain specific functionalities requires the ability to resolve the state and concentration of local oxygen defects across buried interfaces. In this work, we utilized a novel combination of hard X-ray photoelectron spectroscopy (HAXPES) and high resolution X-ray diffraction (HRXRD) to probe the local oxygen defect distribution across the buried interfaces of oxide heterolayers. This approach provides a nondestructive way to qualitatively probe locally the oxygen defects in transition metal oxide heterostructures. We studied two trilayer structures as model systems: the La0.8Sr0.2CoO3−δ/(La0.5Sr0.5)2CoO4−δ/La0.8Sr0...

Structural defects in the molybdenum disulfide (MoS2) monolayer are widely known for strongly altering its properties. Therefore, a deep understanding of these structural defects and how they affect MoS2 electronic properties is of fundamental importance. Here, we report on the incorporation of atomic hydrogen in mono-layered MoS2 to tune its structural defects. We demonstrate that the electronic properties of single layer MoS2 can be tuned from the intrinsic electron (n) to hole (p) doping via controlled exposure to atomic hydrogen at room temperature. Moreover, this hydrogenation process represents a viable technique to completely saturate the sulfur vacancies present in the MoS2 flakes. The successful incorporation of hydrogen in MoS2 leads to the modification of the electronic properties as evidenced by high resolution X-ray photoemission spectroscopy and density functional theory calculations. Micro-Raman spectroscopy and angle resolved photoemission spectroscopy measurements show the high quality of the hydrogenated MoS2 confirming the efficiency of our hydrogenation process. These results demonstrate that the MoS2 hydrogenation could be a significant and efficient way to achieve tunable doping of transition metal dichalcogenides (TMD) materials with non-TMD elements., 15 pages, 6 figures + SI 3 pages 3 figures. Pre-print published with the authorization of ACS Publications

The electric field control of functional properties is a crucial goal in oxide-based electronics. Non-volatile switching between different resistivity or magnetic states in an oxide channel can be achieved through charge accumulation or depletion from an adjacent ferroelectric. However, the way in which charge distributes near the interface between the ferroelectric and the oxide remains poorly known, which limits our understanding of such switching effects. Here we use a first-of-a-kind combination of scanning transmission electron microscopy with electron energy loss spectroscopy, near-total-reflection hard X-ray photoemission spectroscopy, and ab-initio theory to address this issue. We achieve a direct, quantitative, atomic-scale characterization of the polarization-induced charge density changes at the interface between the ferroelectric BiFeO3 and the doped Mott insulator Ca1-xCexMnO3, thus providing insight on how interface-engineering can enhance these switching effects., Work supported by ERC Consolidator grant MINT (Contract No. 615759)