Heterojunctions are the backbone of established semiconductor technology. The highly desirable reliable creation of dielectrically defined heterojunctions in transition metal dichalcogenide monolayers (TMD-MLs) requires an in-depth understanding of dielectric screening effects induced by the ML's environment. Here we report on the modulations of excitonic transitions in TMD-MLs through the effect of dielectric environments including low-$k$ and high-$k$ dielectric materials. We present absolute tuning ranges as large as 37 meV for the optical band gaps of ${\mathrm{WSe}}_2$ and ${\mathrm{MoSe}}_2$ MLs and relative tuning ranges on the order of 15% for the binding energies of charged excitons. Additionally, we measure relative changes of 30% in the energy splittings of exciton Rydberg states of ${\mathrm{WSe}}_2$. The findings enable us to estimate changes in the exciton binding energies and the electronic band gaps of the studied materials.

• Received 18 July 2017
• Revised 10 August 2017

DOI:https://doi.org/10.1103/PhysRevMaterials.1.054001