CVD hexagonal boron nitride (h-BN) tunneling layer was used to reduce the Schottky barrier height and improve the contact between metal and MoS2. A MoS2 flake was mechanically exfoliated onto the SiO2/Si (255 nm thick thermal oxide) substrate by the scotch tape method. CVD h-BN was then transferred onto the substrate to cover the entire MoS2. The thickness of the CVD grown h-BN was confirmed to be 1-2 layers by atomic force microscopy (AFM) measurement at the edge of the film. The thickness of these MoS2flakes was evaluated to be 4-5 layers by optical microscopy and Raman spectroscopy. After the coverage of CVD h-BN, the turn-on voltage showed a small negative shift compared with the MoS2 -metal contact, which was also observed in previous works on tunneling contact. As the current is determined by both the channel and the contact for a Schottky contact transistor, the transistor becomes easier to be turned on when the contact resistance is reduced. The penetration of metal induced gap state (MIGS) results in the high Schottky barrier height for metal contact. Inserting a h-BN layer does not alter the MoS2bands, indicating weakened interaction at the interface. The penetration of MIGS is reduced by using the atomic h-BN insulator, which results in a reduced Schottky barrier height.
- contact resistance
- hexagonal boron nitride