© 2016 American Chemical Society. The nature and extent of electronic screening at heterointerfaces and their consequences on energy level alignment are of profound importance in numerous applications, such as solar cells, electronics etc. The increasing availability of two-dimensional (2D) transition metal dichalcogenides (TMDs) brings additional opportunities for them to be used as interlayers in "van der Waals (vdW) heterostructures" and organic/inorganic flexible devices. These innovations raise the question of the extent to which the 2D TMDs participate actively in dielectric screening at the interface. Here we study perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) monolayers adsorbed on single-layer tungsten diselenide (WSe2), bare graphite, and Au(111) surfaces, revealing a strong dependence of the PTCDA HOMO-LUMO gap on the electronic screening effects from the substrate. The monolayer WSe2 interlayer provides substantial, but not complete, screening at the organic/inorganic interface. Our results lay a foundation for the exploitation of the complex interfacial properties of hybrid systems based on TMD materials.
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: The authors thank Zhuo Wang and Qixing Wang for helping us with transferring the CVD-WSe2 samples and checking the sample quality, Prof. Satoshi Kera and Kyushu Synchrotron Light Research Center (Japan) for ARPES mapping of the clean Au(111) surface, as well as Xin Luo, Kapildeb Dolui, Suchun Li and Zijing Ding for discussions. A.T.S.W. acknowledges support from MOE Grant R-144-000-321-112. S.Y.Q, and Y.C. acknowledge support from Grant NRF-NRFF2013-07 from the National Research Foundation, Singapore. G.E. acknowledges support from Grant NRF-NRFF2011-02 from the National Research Foundation, Singapore. Computations were performed on the NUS Graphene Research Centre cluster. We acknowledge support from the Singapore National Research Foundation, Prime Minister's Office, under its medium-sized centre program. Sandia National Laboratories is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Co., for the U.S. DOE under contract DE-AC04-94AL85000.