Special CPM Seminar

Scalable synthesis of WS2 on graphene and h-BN: an all-2D platform for light-matter transduction

Antonio Rossi

Scuola Normale Superiore, Pisa

By exhibiting a measurable bandgap and exotic valley physics, atomically-thick tungsten disulfide (WS2) offers exciting prospects for optoelectronic applications. The synthesis of continuous WS2 films on other two-dimensional (2D) materials would greatly facilitate the implementation of novel all-2D photoactive devices [1-3]. We have demonstrated the scalable growth of WS2 on graphene and hexagonal boron nitride (h-BN) via a chemical vapor deposition (CVD) approach. Spectroscopic and microscopic analysis reveal that the film is bilayer-thick, with local monolayer inclusions. Photoluminescence measurements show a remarkable conservation of polarization at room temperature peaking 74% (Fig. 1a-b) for the entire WS2 film. Furthermore, we present a scalable approach for the design of photoconductive and photoemitting patterns. By adopting epitaxial graphene on SiC as growth substrate, one can define in a bottom-up fashion photoemitting and photoconducting ribbons (Fig. 1c). The scalable synthesis and design on 2D substrates of WS2 films with outstanding optical properties is instrumental in the development of novel all-2D quantum optoelectronic and valleytronic devices.

References:
[1] M. Chhowalla, H. S. Shin, G. Eda, L.-J. Li, K. P. Loh, H. Zhang, Nature Chemistry 2013, 5, 263.
[2] H.-P. Komsa, A. V. Krasheninnikov, Physical Review B 2013, 88, 085318.
[3] Q. H. Wang, K. Kalantar-Zadeh, A. Kis, J. N. Coleman, M. S. Strano, Nature Nanotechnology 2012, 7, 699

Figure 1. (a) PL intensity map of a selected h-BN flake (also shown in the optical micrograph in the inset (b) PL polarization vs. PL intensity 2D histogram. The polarization peaks at ~74%. (c) PL intensity map taken from the area shown in the inset. The emission in stronger where WS2 is on top of buffer layer regions.