Investigation of Band Alignment at Two-Dimensional Xse2/Res2 (X=W, Mo) Heterojunctions Using X-Ray/Ultraviolet Photoelectron Spectroscopy

In this work, the monolayer WSe 2 and MoSe 2 were transferred to the surface of ReS 2 /sapphire to form two-dimensional (2D) WSe 2 /ReS 2 and MoSe 2 /ReS 2 van der Waal heterojunctions, respectively. The high quality of monolayer ReS 2 , WSe 2 and MoSe 2 was characterized by Raman spectroscopy. We determined a valence band offset of 0.16±0.15 eV at WSe 2 /ReS 2 heterojunction using x-ray photoelectron spectroscopy, with a type-II band alignment. The valence band offset of MoSe 2 /ReS 2 was determined to be 0.61±0.15 eV, with a type-I band alignment. y combining ultraviolet photoelectron spectroscopy, the Anderson’s affinity rule was used to validate the XPS results. This work not only reveals energy-band structures of the WSe 2 /ReS 2 interface and MoSe 2 /ReS 2 interface, but also paves the way for the future designing of 2D heterojunction-based optoelectronic devices.