Metal contacts to MoS2: A two-dimensional semiconductor

With increasing demands for electrostatic control as scaling continues in today's transistors, low dimensional structures continue to gain attention as a pathway for future device scaling because they offer excellent electrostatic control while remaining compatible with straightforward lithography techniques. In particular, MoS2 has attracted interest for transistor applications because its large band gap allows for field effect devices with low off-current, unlike graphene [1]. One key bottleneck, however, is the realization of ohmic contacts on MoS2 to improve FET device on-state performance. With this in mind, we evaluate Ni and Pd contacts on MoS2 as potential alternatives to the already realized Au-MoS2 and Ti-MoS2 contacts [1]. Back-gated transfer length method (TLM) structures with Au, Ni, and Pd contact metals were fabricated on exfoliated MoS2 flakes, with 300nm SiO2 on degenerately doped Si as the substrate. The data indicate that Ni, like Au, makes an ohmic contact to the n-doped MoS2 while the Pd metal contact shows Schottky behavior.