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Hydrogen-induced Sulfur Vacancies on the MoS2 Basal Plane Studied by Ambient Pressure XPS and DFT Calculations |
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| Authors: | Fumihiko Ozaki Dr. Shunsuke Tanaka YoungHyun Choi Dr. Wataru Osada Kozo Mukai Dr. Mitsuaki Kawamura Dr. Masahiro Fukuda Dr. Masafumi Horio Prof. Dr. Takanori Koitaya Prof. Dr. Susumu Yamamoto Prof. Dr. Iwao Matsuda Prof. Dr. Taisuke Ozaki Prof. Dr. Jun Yoshinobu |
| Affiliation: | 1. The Institute for Solid State Physics, The University of Tokyo, 5-1-5, Kashiwanoha, 277-8581 Kashiwa, Chiba, Japan Contribution: Conceptualization (lead), Investigation (lead), Writing - original draft (lead), Writing - review & editing (equal);2. The Institute for Solid State Physics, The University of Tokyo, 5-1-5, Kashiwanoha, 277-8581 Kashiwa, Chiba, Japan;3. The Institute for Solid State Physics, The University of Tokyo, 5-1-5, Kashiwanoha, 277-8581 Kashiwa, Chiba, Japan Contribution: Investigation (supporting);4. Information Technology Center, The University of Tokyo, 2-11-16 Yayoi, Bunkyo, 113-8658 Tokyo, Japan;5. Department of Chemistry, Graduate school of Science, Kyoto University, 606-8502 Kyoto, Japan;6. International Center for Synchrotron Radiation Innovation Smart, Tohoku University, 980-8577 Sendai, Miyagi, Japan;7. The Institute for Solid State Physics, The University of Tokyo, 5-1-5, Kashiwanoha, 277-8581 Kashiwa, Chiba, Japan Contribution: Funding acquisition (supporting), Investigation (supporting), Software (lead), Writing - review & editing (supporting) |
| Abstract: | Sulfur vacancy on an MoS2 basal plane plays a crucial role in device performance and catalytic activity; thus, an understanding of the electronic states of sulfur vacancies is still an important issue. We investigate the electronic states on an MoS2 basal plane by ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) and density functional theory calculations while heating the system in hydrogen. The AP-XPS results show a decrease in the intensity ratio of S 2p to Mo 3d, indicating that sulfur vacancies are formed. Furthermore, low-energy components are observed in Mo 3d and S 2p spectra. To understand the changes in the electronic states induced by sulfur vacancy formation at the atomic scale, we calculate the core-level binding energies for the model vacancy surfaces. The calculated shifts for Mo 3d and S 2p with the formation of sulfur vacancy are consistent with the experimentally observed binding energy shifts. Mulliken charge analysis indicates that this is caused by an increase in the electronic density associated with the Mo and S atoms around the sulfur vacancy as compared to the pristine surface. The present investigation provides a guideline for sulfur vacancy engineering. |
| Keywords: | ambient-pressure x-ray photoelectron spectroscopy density functional calculations hydrogen MoS2 sulfur vacancies |