Photoluminescence of monolayer MoS2 on LaAlO3 and SrTiO3 substrates
In an atomically thin-film/dielectric-substrate heterostructure, the elemental physical properties of the atomically thin-film are influenced by the interaction between the thin-film and the substrate. In this article, utilizing monolayer MoS2 on LaAlO3 and SrTiO3 substrates, as well as SiO2 and Gel-film as reference substrates similar to previously reported work [Nano Res, 2014, 7, 561], we systematically investigate the substrate effect on the photoluminescence of monolayer MoS2. We observed significantly substrate-dependant photoluminescence of monolayer MoS2, originating from substrate-to-film charge transfer. We found that SiO2 substrate introduces the most charge doping while SrTiO3 introduces less charge transfer. Through the selection of desired substrate, we are able to induce different amounts of charge into the monolayer MoS2, which consequently modifies the neutral exciton and charged exciton (trion) emissions. Finally, we proposed a band-diagram model to elucidate the relation between charge transfer and the substrate Fermi level and work function. Our work demonstrates that the substrate charge transfer exerts a strong influence on the monolayer MoS2 photoluminescence property, which should be considered during device design and application. The work also provides a possible route to modify the thin-film photoluminescence property via substrate engineering for future device design.