Large-area WS2 Deposited on Sapphire and Its In-Plane Raman and PL Spectral Distributions

Abstract

Large-area and high-quality WS2 monolayer has been fabricated on the Al2O3 substrate. Three typical WS2 configurations were adopted to examine the in-plane spectral properties. For the triangle WS2 monolayer, the PL light region exhibits a large peak wavelength and could be deduced to be the relaxation of the compressed strain of the WS2 monolayer and the low defect density. For triangle WS2 monolayer with multilayer WS2 on center, combining the peak intensity and position results of PL and Raman spectra, the line traces near the side of the center triangle can be demonstrated to be the defects or dislocations due to the exist of the central multilayer WS2. For large-area WS2 monolayer with crystal domain, PL area integrated mapping shows a uniform light region across the whole surface, except the existing dark crystal domain boundary. The dark line traces could be attributed to compressed strain in the WS2 monolayer due to the formation of the WS2/Al2O3 hybrid structure. The in-plane PL and Raman spectra and mapping exhibited in this work reveal the distribution of stress and defects in this system and further clarify the effects of stress and defects on the optoelectronic properties of WS2 monolayer on Al2O3.