Promoting weak coupling of monolayer ZnSe with noble metal substrates

In the field of optoelectronics, two-dimensional (2D) materials with tunable interfacial structures and bandgap demonstrate significant potential. This study examines ZnSe, a representative II–VI binary compound, synthesized as a monolayer on single-crystal noble metal surfaces. The interfacial structure evolution and electronic interaction were investigated by scanning tunneling microscopy/spectroscopy in conjunction with theoretical calculations. On the Au(111) substrate, the twist angle between ZnSe and Au(111) transitions from 19° to 0° upon annealing, accompanied by reduced interfacial coupling due to decreased charge doping from Au(111). While ZnSe exhibits metallic features on Au(111), it displays semiconducting characteristics with a small bandgap on the Ag(111) substrate, indicating substantially weaker interfacial interaction with Ag(111) compared to Au(111). This research paves a practical way for achieving a tunable bandgap in monolayer ZnSe, presenting a promising candidate for photocatalysis and photodetector applications.