Tuning the electronic properties of WS₂/Sc₂C heterostructures via surface functionalization: a first-principles study

This study, based on first-principles calculations using density functional theory (DFT), investigates the electronic properties of WS₂/Sc₂C heterostructures regulated by surface functionalization with hydrogen (H) and fluorine (F) atoms. The WS₂/Sc₂C heterostructure is composed of monolayer WS₂ (a direct bandgap semiconductor) and monolayer Sc₂C (a metallic MXene). In the absence of functionalization, strong interfacial coupling leads to the metallization of the WS₂ layer, resulting in the metallic behavior of the heterostructure. After hydrogen atom functionalization of the Sc₂C layer, the interfacial coupling is weakened, leading to a transition of the heterostructure into an indirect semiconductor with a bandgap of approximately 0.49 eV. Upon fluorine atom functionalization of the Sc₂C layer, the interfacial coupling is further weakened, resulting in an indirect bandgap of approximately 0.29 eV. By applying an electric field within a certain range to two heterostructures with semiconductor properties (WS₂/Sc₂CH₂ and WS₂/Sc₂CF₂), it was found that the type of their band alignment can be controlled by adjusting the magnitude of the applied electric field. Optical property analyses of the two semiconducting heterostructures reveal significant absorption in the ultraviolet to blue-light region and a broad absorption range, indicating the potential application of these two heterostructures in optoelectronic devices. This work offers valuable insights into the role of surface functionalization in tuning the physical properties of two-dimensional heterostructures and provides theoretical guidance for future electronic and photonic device development.