Electronic characterization of single-layer MoS 2 sheets exfoliated on SrTiO 3

Single layer regions of MoS 2 on SiO 2 and SrTiO 3 were identified by Raman spectroscopy and μ-photoluminescence before Kelvin probe force microscopy was performed. For the already known system MoS 2 /SiO 2 we find 1.839 eV for the direct bandgap, in good agreement with earlier results. On MoS 2 /SrTiO3 the direct bandgap was determined to be 1.829 eV. From our Kelvin probe data we infer that the SrTiO 3 substrate leads to a dipole layer at the interface of the MoS 2 single layer. The corresponding μ-PL measurements however show no significant decrease of the bandgap. This shows, that in the case of MoS 2 the carrier type as well as concentration is not significantly influenced by the choice of SrTiO 3 as the substrate compared to SiO 2 .