Visualizing the metal-MoS2 contacts in two-dimensional field-effect transistors with atomic resolution

Two-dimensional MoS2 is an excellent channel material for ultrathin field-effect transistors, but high contact resistance across the deposited metal-MoS2 interface continues to limit its full realization. Using atomic-resolution scanning transmission electron microscopy and first-principles calculations, we showed that deposited metals with a high affinity for sulfur could have a fundamental limitation. Ti-MoS2 contact shows a destruction of the MoS2 layers, a formation of clusters and void pockets, and penetration of Ti into MoS2, resulting in many localized pinning states in the band gap. InAu-MoS2 contact shows that it is possible to achieve a van der Waals-type interface and dramatically reduced pinning states.