| AVS 63rd International Symposium & Exhibition | |
| 2D Materials Focus Topic | Thursday Sessions |
| Session 2D-ThA |
| Session: | Surface Chemistry, Functionalization, Bio and Sensor Applications of 2D Materials |
| Presenter: | Kathleen McCreary, Naval Research Laboratory |
| Authors: | K.M. McCreary, Naval Research Laboratory A.T. Hanbicki, Naval Research Laboratory G. Kioseoglou, University of Crete M. Currie, Naval Research Laboratory B.T. Jonker, Naval Research Laboratory |
| Correspondent: | Click to Email |
The unique electronic band structure in single layer WS2 provides the ability to selectively populate a desired valley by exciting with circularly polarized light. The valley population is reflected through the circular polarization of photoluminescence (PL). We investigate the circularly polarized PL in WS2 monolayers synthesized on SiO2/Si substrates using chemical vapor deposition (CVD).[1] The resulting polarization is strongly dependent on the sample preparation. As-grown CVD WS2 (still on the growth substrate) exhibits PL emission from the neutral exciton and polarized emission that is unaffected by laser power. Removing WS2 from the growth substrate and repositioning on the same substrate significantly impacts the optical properties. In transferred films, the excitonic state is optically controlled via high-powered laser exposure such that subsequent PL is from either the charged exciton state or the neutral exciton state, similar to the recently observed behavior in mechanically exfoliated WS2 flakes.[2] Additionally, the neutral excitonic emission in transferred CVD films exhibits low polarization whereas the trion polarization can exceed 25% at room temperature, demonstrating the ability to optically control the degree of circularly polarized emission. The removal process may modify the strain, sample-to-substrate distance, and chemical doping in the WS2 monolayer, and work is underway to determine how these factors influence the valley populations. This work was supported by core programs at NRL and the NRL Nanoscience Institute, and by the Air Force Office of Scientific Research #AOARD 14IOA018-134141.
[1] K. M. McCreary, A. T. Hanbicki, G. G. Jernigan, J. C. Culbertson, B. T. Jonker, Sci. Rep.2016, 6, 19159.
[2] M. Currie, A. T. Hanbicki, G. Kioseoglou, B. T. Jonker, Appl. Phys. Lett.2015, 106, 201907.