Annealed Ag contacts to MoS₂ field-effect transistors

Silver contacts to few-layer (5 to 14 layers thick) MoS₂ have been studied before and after annealing. Annealing was found to be critical for reducing the contact resistance but did not degrade the operation of field-effect transistors that are part of the test structure. The contact resistance for the as-deposited samples was in the range of 0.8-3.5 kΩ μm. On the other hand, the contact resistance was reduced to 0.2-0.7 kΩ μm, evaluated at a constant sheet resistance of 32 kΩ/□, after annealing at 250 or 300 °C. The reduced contact resistance is attributed to diffusion of Ag into the MoS₂ and doping, as supported by further electrical characterization of the contacts and devices.