Exciton broadening in WS2 /graphene heterostructures

Abstract

We have used optical spectroscopy to observe spectral broadening of ${\mathrm{WS}}_{2}$ exciton reflectance peaks in heterostructures of monolayer ${\mathrm{WS}}_{2}$ capped with mono- to few-layer graphene. The broadening is found to be similar for the A and B excitons and on the order of 5--10 meV. No strong dependence on the number of graphene layers was observed within experimental uncertainty. The broadening can be attributed to charge- and energy-transfer processes between the two materials, providing an observed lower bound for the corresponding time scales of 65 fs.