Efficiently enhanced the visible-light absorption of monolayer WS2 by constructing an asymmetric Fabry-Perot cavity

Abstract

Abstract Transition metal dichalcogenides (TMDCs) have been intensively researched during the past decade in consequence of their fascinating properties, such as tunable bandgap, high carrier mobility, and extraordinary luminescent efficiency. But compared with their bulk counterparts, atomically thin two-dimensional (2D) TMDCs have an intrinsic lower light absorption (∼5%), preventing them from further applications in optoelectronic area. Commonly, fabrication of high-performance TMDC nanodevices not only requires complicated or expensive process, but also is hard to simultaneously realize significant and uniform enhancement for large-scale planar integrated device applications. Herein, we provided an asymmetric Fabry–Perot (F-P) cavity method to efficiently enhance the light absorption of the monolayer tungsten disulfide (ML WS2). By constructing the F-P cavity structure of WS2/SiO2/Au with an optimal thickness of SiO2 spacer, the visible-light absorptivity of ML WS2 dramatically increased from 5% to 49%. To further testify the enhancement effect of the F-P cavity, this hybrid structure was integrated into photoconductive device and compared with pristine WS2 device. The results showed that the photoresponsivity of the hybrid F-P cavity structure (8.3\xa0A\xa0W−1) was found to be 2 orders higher than that of pristine WS2 (0.028\xa0A\xa0W−1). Moreover, this hybrid structure exhibited a more remarkable and uniform light-field enhancement than pristine WS2 under 532-nm excitation, attributing to the formation of the constructive interference in F-P resonance cavity. This novel F-P cavity structure can shed new light on substantially and uniformly improving the low absorptivity of 2D nanomaterials for future developments.