Probing Interfacial Surface State Excitons in Nanoscale Synthesized Cu_xS/MoS₂ Heterostructure

Abstract Two dimensional (2D) layer integration of different materials facilitates new functionalities in material engineering to produce novel structures with specialized properties. Fabrication of large‐scale 2D heterostructure with atomically clean interface, and unveiling the distinct interlayer transition, is a challenging process. In this paper, the vertical heterostructure of copper sulfide (Cu_xS) and molybdenum disulfide (MoS₂) nanosheets is synthesized by sulfurization of pre‐deposited metal films. Optical bandgap transition and phonon vibration frequency are observed in the heterojunction area with respect to individual nanosheets. Raman shift in phonon vibration modes of MoS₂ shows the interlayer coupling effect. Photoluminescence (PL) intensity of monolayer MoS₂ is quenched due to bandgap offset interlayer transition. Bandgap alignment of Cu_xS (1 < x < 2) with MoS₂ is a tunable staggered symmetry that yields charge transfer at the heterostructure interface. Photoexcited electron–hole pairs are moving across the interface much faster than recombining into the intralayer excitons. The synthesized Cu_xS/MoS₂ heterostructure is well defined over a large area, with controllable thickness and a scalable position. Heterostructure has great potential for future device applications in optoelectronics based on optical excitonic response and charge carrier dynamics.