Using Ar Ion beam exposure to improve contact resistance in MoS2 FETs
Contact resistance is a dominant factor in the performance of field-effect transistors (FETs) from two-dimensional MoS2. Several techniques have been shown to improve carrier transport at the metal-MoS2 interface, thus lowering the contact resistance. These approaches include the use of molecular doping [1], different contact materials [2-5], phase transformation of MoS2 [6], and adding an interfacial oxide at the contacts [7, 8]. The challenges for the most effective of these techniques are that they generally require additional processing, sometimes involving very high temperatures, or the addition of materials at the metal-MoS2 interface that may lower contact resistance but still yield relatively poor FET performance. In graphene, it has been demonstrated that intentionally damaging the crystal lattice in the contact region using O2 plasma can substantially reduce the contact resistance [9-11]. In this work, we examine a related contact engineering approach for MoS2 FETs by using an in situ, broad-beam ion source to modify the MoS2 lattice immediately prior to contact metal deposition. The result is a substantial improvement in key performance metrics, including contact resistance and on-current.
