| AVS 63rd International Symposium & Exhibition | |
| 2D Materials Focus Topic | Thursday Sessions |
| Session 2D-ThP |
| Session: | 2D Materials Poster Session |
| Presenter: | Iori Tanabe, University of Nebraska-Lincoln |
| Authors: | I. Tanabe, University of Nebraska-Lincoln T. Komesu, University of Nebraska - Lincoln E.F. Schwier, Hiroshima Synchrotron Radiation Center M. Gomez, University of California - Riverside L. Bartels, University of California - Riverside M. Zheng, Hiroshima University Y. Kojima, Hiroshima University E.M. Echeverria, University of Nebraska-Lincoln A.V. Barinov, Elettra - Sincrotrone Trieste S.K. Balijepalli, Elettra - Sincrotrone Trieste V. Kandyba, Elettra - Sincrotrone Trieste K. Shimada, Hiroshima Synchrotron Radiation Center P.A. Dowben, University of Nebraska - Lincoln |
| Correspondent: | Click to Email |
WSe2 and WS2 and the related transition metal dichalcogenides (TMDs) MX2 (with M = V, Mo, W, Ta and X = S, Se, Te) are layered structures, where each plane consists of a hexagonal honeycomb lattice reminiscent of graphene or graphite. The distinguishing features of TMDs compared to graphene are that TMDs are semiconductors and TMDs monolayers have C3v symmetry, not C6v symmetry, since the metal and chalcogen planes are offset from each other. We investigated the valence band structure of bulk WSe2 and multilayer WS2 using angle resolved photoemission spectroscopy (ARPES). These ARPES studies of the electronic band structure of bulk WSe2 and multilayer WS2 provide a means to compare the effective hole mass and the splitting of the top of the valence band at K, due to spin-orbit coupling for various transition metal dichalcogenides. The splitting of the top of the valence band at K was measured to be 0.49±0.01 eV and 0.42±0.03 eV, for bulk WSe2 and multilayer WS2 respectively. In both cases, the splitting due to spin orbit coupling are far larger than that for MoS2, but smaller than that for monolayer WSe2. We found that the effective mass at the top of the valence band at K of WSe2 and WS2 were very small, which indicates very high intrinsic mobility and is consistent with expectations from density functional theory. The electron effective masses, as derived from angle-resolved inverse photoemission, are found to be much greater than anticipated.