Contact Resistances to n- and p-type 2D Semiconductors MoS₂ and WSe₂ with Moire Lattice Interfaces

We show how Moire lattices between metal contacts and n-type MoS2 or ambipolar WSe2 layers can favor physisorptive sites with weaker Fermi level pinning rather than chemisorptive sites. This distinction causes a sharp difference in Schottky pinning factor, S. S for physisorbed interfaces is similar to 0.36, while S is a strongly pinned 0.21 for chemisorbed sites. Thus, Ef lies close to the conduction band for physi- In or Ag on MoS2, while Pd lies near the valence band for p-type WSe2. This explains the experimental results for In, Ag and Pd contacts.