Here we report the successful growth of MoSe2 on single layer hexagonal boron nitride (hBN) on Ru(0001) substrate by using molecular beam epitaxy. We investigated the electronic structures of MoSe2 using scanning tunneling microscopy and spectroscopy. Surprisingly, we found that the quasi-particle gap of the MoSe2 on hBN/Ru is about 0.25 eV smaller than those on graphene or graphite substrates. We attribute this result to the strong interaction between hBN/Ru which causes residual metallic screening from the substrate. The surface of MoSe2 exhibits Moire pattern that replicates the Moire pattern of hBN/Ru. In addition, the electronic structure and the work function of MoSe2 are modulated electrostatically with an amplitude of ~ 0.13 eV. Most interestingly, this electrostatic modulation is spatially in phase with the Moire pattern of hBN on Ru(0001) whose surface also exhibits a work function modulation of the same amplitude.
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