Carrier density in monolayer MoS$_2$ govern by hBN encapsulation -- unveiling of negative trion's fine structure

摘要: Atomically thin materials, like semiconducting transition metal dichalcogenides, are highly sensitive to the environment. This opens up an opportunity externally control their properties by changing surroundings. The optical response of monolayer MoS$_2$ encapsulated in hexagonal BN (hBN) is studied with aid photoluminescence and reflectance contrast experiments. We demonstrate that carrier concentration monolayers can be significantly tuned from $n$-type doping free-electron about 2 $\times$ 10$^{12}$ cm$^{-2}$, through neutrality point, ending natural $p$-type MLs achieved modification bottom hBN flake thickness 4 nm 134 nm. fine structure negatively charged excitons also resolved due high quality investigated structures. propose observed components negative trion originate intravalley singlet, intervalley triplet states.