Contact Resistance at MoS₂-Based 2D Metal/Semiconductor Lateral Heterojunctions

The contact resistance at lateral 1T-MoS2/2H-MoS2 heterostructures is theoretically studied, using first-principles simulations based on density functional theory and the nonequilibrium Green’s function method. The computed contact resistance lies between 30 and 40 kΩ μm and is weakly dependent on the contact edge symmetry (armchair or zigzag). These values are about 2 orders of magnitude larger than the experimental ones reported recently on MoS2-based metal/semiconductor lateral heterojunctions. This discrepancy can be explained by considering the interaction of 1T-MoS2 with various chemical species (H, Li, or H2O) present during the local transformation of semiconducting 2H-MoS2 into metallic 1T-MoS2. The functionalization of 1T-MoS2 by these atoms or molecules results in the decrease of its workfunction, leading to contact resistances in the range of few hundred Ω μm.