Local strain and tunneling current modulated excitonic luminescence in MoS2 monolayers

The excitonic luminescence of monolayer molybdenum disulfide (MoS 2 ) on a gold substrate is studied by scanning tunneling microscopy (STM). STM-induced light emission (STM-LE) from MoS 2 is assigned to the radiative decay of A and B excitons. The intensity ratio of A and B exciton emission can be modulated by the tunneling current, since the A exciton emission intensity saturates at high tunneling currents. Moreover, the corrugated gold substrate introduces local strain to the monolayer MoS 2 , resulting in significant changes of electronic bandgap and valence band splitting. The modulation rates of strain on A and B exciton energies are estimated as -72 meV/% and -57 meV/%, respectively. STM-LE provides a direct link between exciton energy and local strain in monolayer MoS 2 with a spatial resolution <10 nm.