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${}^{\ensuremath{-}}$ (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 $\ensuremath{\approx}80$ meV. Furthermore, the photoluminescence spectra of suspended ${\text{MoS}}_{2}$ can be influenced by interference effects.