Local strain and tunneling current modulate excitonic luminescence in MoS2 monolayers

Abstract

The excitonic luminescence of monolayer molybdenum disulfide (MoS₂) on a gold substrate is studied by scanning tunneling microscopy (STM). STM-induced light emission (STM-LE) from MoS₂ is assigned to the radiative decay of A and B excitons. The intensity ratio of A and B exciton emission is 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 MoS₂, resulting in significant changes of electronic bandgap and valence band splitting. The modulation rate of strain on A exciton energy is estimated as −69 ± 5 meV/%. STM-LE provides a direct link between exciton energy and local strain in monolayer MoS₂ on a length scale of 10 nm.