  In this paper, we report a novel chemical doping technique to reduce the
contact resistance (Rc) of transition metal dichalcogenides (TMDs) -
eliminating two major roadblocks (namely, doping and high Rc) towards
demonstration of high-performance TMDs field-effect transistors (FETs). By
using 1,2 dichloroethane (DCE) as the doping reagent, we demonstrate an active
n-type doping density > 2*1019 cm-3 in a few-layer MoS2 film. This enabled us
to reduce the Rc value to a record low number of 0.5 kohm*um, which is ~10x
lower than the control sample without doping. The corresponding specific
contact resistivity (pc) is found to decrease by two orders of magnitude. With
such low Rc, we demonstrate 100 nm channel length (Lch) MoS2 FET with a drain
current (Ids) of 460 uA/um at Vds = 1.6 V, which is twice the best value
reported so far on MoS2 FETs.
