Direct exciton emission from atomically thin transition metal dichalcogenide heterostructures near the lifetime limit.

ABSTRACT: We demonstrate the reduction of the inhomogeneous linewidth of the free excitons in atomically thin transition metal dichalcogenides (TMDCs) MoSe₂, WSe₂ and MoS₂ by encapsulation within few nanometre thick hBN. Encapsulation is shown to result in a significant reduction of the 10?K excitonic linewidths down to ?3.5?meV for n-MoSe₂, ?5.0??meV for p-WSe₂ and ?4.8?meV for n-MoS₂. Evidence is obtained that the hBN environment effectively lowers the Fermi level since the relative spectral weight shifts towards the neutral exciton emission in n-doped TMDCs and towards charged exciton emission in p-doped TMDCs. Moreover, we find that fully encapsulated MoS₂ shows resolvable exciton and trion emission even after high power density excitation in contrast to non-encapsulated materials. Our findings suggest that encapsulation of mechanically exfoliated few-monolayer TMDCs within nanometre thick hBN dramatically enhances optical quality, producing ultra-narrow linewidths that approach the homogeneous limit.

SUBMITTER: Wierzbowski J 

PROVIDER: S-EPMC5620059 | biostudies-literature | 2017 Sep

REPOSITORIES: biostudies-literature