Enhancement of photoluminescence of monolayer transition metal dichalcogenide by subwavelength TiO<sub>2</sub> grating

Transition metal dichalcogenide (TMDC) monolayers have direct band gaps and can produce strong photoluminescence(PL), thereby possessing a wide application prospect in photoelectric devices and photoelectric detection fields. However, their PL efficiency needs further improving because they are of atomic thickness only, besides, they have non-radiative recombination of excitons. In this study, a combination structure of a gold film, titanium dioxide subwavelength gratings and TMDC monolayers is designed, which can greatly improve PL efficiency of the TMDC monolayers. The spontaneous emission rate can be controlled by the Purcell effect, and the maximum enhancement of photoluminescence is as high as 3.4 times. In this paper, the PL signals of monolayer WS₂ and monolayer WSe₂ on the designed structure are studied. The feasibility of the enhancement of PL of the TMDC monolayers on the subwavelength grating structure is verified experimentally, which provides a new idea for the application of two-dimensional materials to optoelectronic devices.