Experimental Determination of the Ionization Energies of MoSe2, WS2, and MoS2 on SiO2 Using Photoemission Electron Microscopy
| Autor: | Thomas E. Beechem, Pulickel M. Ajayan, Xiang Zhang, Kunttal Keyshar, Gautam Gupta, Morgann Berg, Calvin K. Chan, Taisuke Ohta, Robert Vajtai, Aditya D. Mohite |
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| Rok vydání: | 2017 |
| Předmět: |
Chemistry
business.industry Exciton General Engineering General Physics and Astronomy Heterojunction 02 engineering and technology 010402 general chemistry 021001 nanoscience & nanotechnology 01 natural sciences 0104 chemical sciences Brillouin zone Condensed Matter::Materials Science Photoemission electron microscopy Semiconductor Valleytronics General Materials Science Density functional theory Ionization energy Atomic physics 0210 nano-technology business |
| Zdroj: | ACS Nano. 11:8223-8230 |
| ISSN: | 1936-086X 1936-0851 |
| Popis: | The values of the ionization energies of transition metal dichalcogenides (TMDs) are needed to assess their potential usefulness in semiconductor heterojunctions for high-performance optoelectronics. Here, we report on the systematic determination of ionization energies for three prototypical TMD monolayers (MoSe2, WS2, and MoS2) on SiO2 using photoemission electron microscopy with deep ultraviolet illumination. The ionization energy displays a progressive decrease from MoS2, to WS2, to MoSe2, in agreement with predictions of density functional theory calculations. Combined with the measured energy positions of the valence band edge at the Brillouin zone center, we deduce that, in the absence of interlayer coupling, a vertical heterojunction comprising any of the three TMD monolayers would form a staggered (type-II) band alignment. This band alignment could give rise to long-lived interlayer excitons that are potentially useful for valleytronics or efficient electron–hole separation in photovoltaics. |
| Databáze: | OpenAIRE |
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