Type-II Interface Band Alignment in the vdW PbI 2 -MoSe 2 Heterostructure.

Energy band alignments at heterostructure interfaces play key roles in device performance, especially between two-dimensional atomically thin materials. Herein, van der Waals PbI-MoSe heterostructures fabricated by PbI deposition on monolayer MoSe are comprehensively studied using scanning tunneling microscopy/spectroscopy, atomic force microscopy, photoemission spectroscopy, and Raman and photoluminescence (PL) spectroscopy. PbI grows on MoSe in a quasi layer-by-layer epitaxial mode. A type-II interface band alignment is proposed between PbI and MoSe with the conduction band minimum (valence band maximum) located at PbI (MoSe), which is confirmed by first-principles calculations and the existence of interfacial excitons revealed using temperature-dependent PL. Our findings provide a scalable method to fabricate PbI-MoSe heterostructures and new insights into the electronic structures for future device design.