Electroluminescence of monolayer WS${}_2$ in a scanning tunneling microscope: the effect of bias polarity on the spectral and angular distribution of the emitted light

Abstract

Inelastic electron tunneling in a scanning tunneling microscope (STM) is used to generate excitons in monolayer tungsten disulfide (WS${}_2$). Excitonic electroluminescence is measured both at positive and negative sample bias. Using optical spectroscopy and Fourier-space optical microscopy, we show that the bias polarity of the tunnel junction determines the spectral and angular distribution of the emitted light. At positive sample bias, only emission from excitonic species featuring an in-plane transition dipole moment is detected. Based on the spectral distribution of the emitted light, we infer that the dominant contribution is from charged excitons, i.e., trions. At negative sample bias, additional contributions from lower-energy excitonic species are evidenced in the emission spectra and the angular distribution of the emitted light reveals a mixed character of in-plane and out-of-plane transition dipole moments.

References in corpus (2)

• Excitonic complexes in $n$-doped WS${}_2$ monolayer
• Tunneling-current-induced local excitonic luminescence in p-doped WSe${}_2$ monolayers

Cited by in corpus (3)

• Active control of excitonic strong coupling and electroluminescence in electrically driven plasmonic nanocavities
• Nano-optics of transition metal dichalcogenides and their van der Waals heterostructures with electron spectroscopies
• Sub-diffraction-resolved spatial distribution of emitting excitons in STM-induced luminescence of 2D semiconductors via Richardson-Lucy deconvolution