Strain-sensitive optical properties of monolayer tungsten diselenide

Abstract

As representative layered quantum materials, monolayer (1L) transition metal dichalcogenides (TMDs) have optical and electronic properties that can be controlled by crystal strain, allowing expanded applications using strain engineering. Raman and Photoluminescence (PL) spectroscopy are the most widely used analytical tools for studying strain in 1L TMDs. Although studies have been reported on strain engineering of 1L TMDs, only results with strain greater than 0.2 % have been reported. To precisely control the strain of 1L TMDs and expand their applications, it is necessary to systematically study the changes in optical properties at low strain. This work investigated the optical property, which changes sensitively at low strains below 0.2 % of 1L TMD, using an Au honeycomb pattern template (HPT). 1L WSe2 grown by chemical vapor deposition was transferred to an Au HPT, and the strain-induced changes in optical properties were evaluated using confocal Raman and PL spectroscopy. Interestingly, Raman scattering, known to be sensitive to strain, was not changed at strains of less than 0.2 %, while the PL properties were sensitively changed at low strains in 1L WSe2. The PL properties of 1L WSe2, sensitive to strain as low as 0.2 %, have been theoretically verified by density functional theory calculations.