Photoluminescence of freestanding single- and few-layer MoS2

We present a photoluminescence study of freestanding and Si/SiO2 supported single- and few-layer MoS2. The single-layer exciton peak (A) is only observed in freestanding MoS2. The photoluminescence of supported single-layer MoS2 is instead originating from the A- (trion) peak as the MoS2 is n-type doped from the substrate. In bilayer MoS2, the van der Waals interaction with the substrate is decreasing the indirect band gap energy by up to ~ 80 meV. Furthermore, the photoluminescence spectra of suspended MoS2 can be influenced by interference effects.