Local strain and tunneling current modulate excitonic luminescence in MoS monolayers.

The excitonic luminescence of monolayer molybdenum disulfide (MoS) on a gold substrate is studied by scanning tunneling microscopy (STM). STM-induced light emission (STM-LE) from MoS is assigned to the radiative decay of and excitons. The intensity ratio of and exciton emission is modulated by the tunneling current, since the exciton emission intensity saturates at high tunneling currents. Moreover, the corrugated gold substrate introduces local strain to the monolayer MoS, resulting in significant changes of electronic bandgap and valence band splitting. The modulation rate of strain on exciton energy is estimated as -69 ± 5 meV/%. STM-LE provides a direct link between exciton energy and local strain in monolayer MoS on a length scale of 10 nm.