Interface Dipole Engineering at the Au/n-MoSe₂ Nanosheet Contact for Both Schottky and Ohmic-like Device Operation

Controlling metal/van der Waals (vdW) semiconductor interfaces has been an issue related to the importance of source/drain contacts in field-effect transistors (FETs). Here, we report our findings, which could offer direct methods for controlling the interface of the metal/vdW system. Regarding our model system, the Au/n-MoSe2 nanosheet interface, the top Au contact apparently displays Schottky contact because sputter-deposited Au causes disordered interface dipoles. In contrast, the bottom Au contact beneath a dry-transferred n-MoSe2 nanosheet shows Ohmic-like behavior, which means that the interface dipoles are well-ordered. Likewise, dipole-induced Fermi-level pinning effects are modulated or engineered by means of disordering. For device applications, we simply use the bottom Au/n-MoSe2 nanosheet contact to achieve high-performance FETs, and we also achieve a strong rectifying diode from the top Au/MoSe2/bottom Au assembly. Such interface-dipole engineering appears most desirable for the Au/n-MoSe2 system enabling both Schottky and Ohmic-like characteristics, while it seems more limited for other metal/vdW systems.