Photoluminescence of freestanding single- and few-layerMoS2

Abstract

We present a photoluminescence study of freestanding and Si/${\text{SiO}}_2$ supported single- and few-layer ${\text{MoS}}_2$. The single-layer exciton peak (A) is only observed in freestanding ${\text{MoS}}_2$. The photoluminescence of supported single-layer ${\text{MoS}}_2$ instead originates from the A${}^{-}$ (trion) peak as the ${\text{MoS}}_2$ is $n$-type doped from the substrate. In bilayer ${\text{MoS}}_2$, the van der Waals interaction with the substrate decreases the indirect band gap energy by up to $\approx 80$ meV. Furthermore, the photoluminescence spectra of suspended ${\text{MoS}}_2$ can be influenced by interference effects. DOI: http://dx.doi.org/10.1103/PhysRevB.89.125406 ©2014 American Physical Society