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 <i>A</i> and <i>B</i> excitons. The intensity ratio of <i>A</i> and <i>B</i> exciton emission is modulated by the tunneling current, since the <i>A</i> 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 <i>A</i> 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.