Self-Terminated Surface Monolayer Oxidation Induced Robust Degenerate Doping in MoTe₂ for Low Contact Resistance

We introduce an effective method to degenerately dope MoTe₂ by oxidizing its surface into the p-dopant MoO in oxygen plasma. As a self-terminated process, the oxidation is restricted only in the very top layer, therefore offering us an easy and efficient control. The degenerate p-doping with the hole concentration of 2.5 × 10¹³ cm^-2 can be obtained by applying a ∼300 s O₂ plasma treatment. Using the degenerately doped MoTe₂, we demonstrate a record low contact resistance of 0.6 kΩ μm for MoTe₂. Our measurement highlights an excellent stability for the plasma-doped MoTe₂. The doped characteristics are robust with no significant degradation even after a one-year exposure to the air. The oxygen plasma doping technique is compatible with the conventional semiconductor processes, which can be utilized to realize high-performance MoTe₂ field-effect transistors (FETs) or tunnel FETs in the future.