Engineering bandgaps of monolayer MoS2 and WS2 on fluoropolymer   substrates by electrostatically tuned many-body effects
  Intrinsic electrical and excitonic properties of monolayer transition metal dichalcogenides are studied on CYTOP fluoropolymer substrates with greatly suppressed unintentional doping and dielectric screening. Ambipolar transport behavior is observed in monolayer WS2 by applying solid states backdates. The excitonic properties of monolayer MoS2 and WS2 are determined by intricate interplays between the bandage renormalization, Pauli blocking and carrier screening against carrier doping. 
Bo Liu, Weijie Zhao, Zijing Ding, Ivan Verzhbitskiy, Linjun Li,   Junpeng Lu, Jianyi Chen, Goki Eda and Kian Ping Loh
cond-mat.mtrl-sci