Conformal Growth of Nano‐Patterned Monolayer MoS2 with Periodic Strain via Patterned Substrate Engineering for High‐performance Photodetectors

Abstract

AbstractThe extraordinary mechanical compliance of 2D molybdenum disulfide (MoS2) makes it an ideal candidate for strain modulation of various electrical and optical properties. However, developing facile methods for accurate and stable engineering of strain still remains a major challenge. Here, a novel and effective method is demonstrated for introducing periodic strain into monolayer MoS2 by direct growth on nano‐patterned sapphire substrates (NPSS). A mixed aqueous solution of Na2MoO4 and NaOH is spin‐coated on the NPSS and sulfurated in one step by chemical vapor deposition (CVD). Highly oriented monolayer MoS2 single‐crystal nanosheets with high quality and few sulfur vacancies are achieved conformally on the NPSS via a liquid‐mediated growth mode. Notably, the periodically distributed blue shift of the PL emission peak demonstrated periodic compressive strain is introduced into the nano‐patterned MoS2 via the thermal expansion difference between MoS2 and substrates. Furthermore, photodetectors fabricated using the nano‐patterned monolayer MoS2 exhibit a high photo‐to‐dark current ratio (PDCR) over 106, an excellent detectivity of 5.4 × 1013 Jones, and a fast photoresponse of 7.7 ms, owing to the strain‐induced back‐to‐back built‐in electric field, enhanced light absorption by light‐scattering effect and fewer S vacancy defects. The scanning imaging demonstration based on the single‐pixel nano‐patterned MoS2 photodetector further confirms its great potential in image sensors. This work hereby presents a pathway for direct conformal growth of nano‐patterned monolayer MoS2 with precisely periodic strain, which should inspire the applications for high‐performance optoelectronic devices via the strategy of patterned substrate engineering by the periodic nanostructures.