The covalently bonded in-plane heterostructure (HS) of monolayer transition-metal dichalcogenides (TMDCs) possesses huge potential for high-speed electronic devices in terms of valleytronics. In this study, high-quality monolayer MoSe2-WSe2 lateral HSs are grown by pulsed-laser-deposition-assisted selenization method. The sharp interface of the lateral HS is verified by morphological and optical characterizations. Intriguingly, photoluminescence spectra acquired from the interface show rather clear signatures of pristine MoSe2 and WSe2 with no intermediate energy peak related to intralayer excitonic matter or formation of MoxW(1-x)Se2 alloys, thereby confirming the sharp interface. Furthermore, the discrete nature of laterally attached TMDC monolayers, each with doubly degenerated but nonequivalent energy valleys marked by (KM, K′M) for MoSe2 and (KW, K′W) for WSe2 in k space, allows simultaneous control of the four valleys within the excitation area without any crosstalk effect over the interface. As an example, KM and KW valleys or K′M and K′W valleys are simultaneously polarized by controlling the helicity of circularly polarized optical pumping, where the maximum degree of polarization is achieved at their respective band edges. The current work provides the growth mechanism of laterally sharp HSs and highlights their potential use in valleytronics.
Bibliographical noteFunding Information:
This research was supported by the Priority Research Centers Program (2009-0093818), the Basic Science Research Programs (2015R1D1A3A03019609, 2016R1A2B4007367, and 2017R1D1A1B03035539), and the Basic Research Lab Program (2014R1A4A1071686) through the National Research Foundation of Korea (NRF), funded by the Korean government. S.H.R. is grateful for support from the National Research Foundation of Korea (2017R1D1A1B04033941).
© 2017 American Chemical Society.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Physics and Astronomy(all)