Band-bending induced by charged defects and edges of atomically thin transition metal dichalcogenide films
Résumé
We report scanning tunneling microscopy/spectroscopy (STM/STS) investigations of the bandbending
in the vicinity of charged point defects and edges of monolayer MoSe$_2$ and mono- and
trilayer WSe$_2$ films deposited on graphitized silicon carbide substrates. By tracing the spatial
evolution of the structures of the STS spectra, we evaluate the magnitude and the extent of the
band-bending to be equal to few hundreds milielectronvolts and several nanometres, respectively.
With the aid of a simple electrostatic model, we show that the spatial variation of the Coulomb
potential close to the film edges can be well reproduced by taking into account the metallic screening
by graphene. Additionally, the analysis of our data for trilayer WSe$_2$ provides reasonable estimations
of its dielectric constant ($\epsilon_{WSe}$$_2$ = 20) and of the magnitude of the charge trapped at the defect site
(Q = $+e$).