Transition metal dichalcogenides (TMDCs) are promising next-generation materials for optoelectronic devices because, at subnanometer thicknesses, they have a transparency, flexibility, and band gap in the near-infrared to visible light range. In this study, we examined continuous, large-area MoSe2 film, grown by molecular beam epitaxy on an amorphous SiO2/Si substrate, which facilitated direct device fabrication without exfoliation. Spectroscopic measurements were implemented to verify the formation of a homogeneous MoSe2 film by performing mapping on the micrometer scale and measurements at multiple positions. The crystalline structure of the film showed hexagonal (2H) rotationally stacked layers. The local strain at the grain boundaries was mapped using a geometric phase analysis, which showed a higher strain for a 30° twist angle compared to a 13° angle. Furthermore, the photon-matter interaction for the rotational stacking structures was investigated as a function of the number of layers using spectroscopic ellipsometry. The optical band gap for the grown MoSe2 was in the near-infrared range, 1.24-1.39 eV. As the film thickness increased, the band gap energy decreased. The atomically controlled thin MoSe2 showed promise for application to nanoelectronics, photodetectors, light emitting diodes, and valleytronics.
Bibliographical noteFunding Information:
Authors acknowledge the financial support from National Research Foundation of Korea (NRF) (Grant No. 2017R1A5A1014862, SRC program vdWMRC center). This work was supported by a NRF grant funded by the Korea government (MSIP) (No. 2015R1A2A1A01007560) and by an Industry-Academy joint research program between Samsung Electronics and Yonsei University. The authors thank Dr. Hee-Suk Chung of the Korea Basic Science Institute at Jeonju for technical assistance in the TEM and STEM measurements.
All Science Journal Classification (ASJC) codes
- Materials Science(all)