Metal-atom-induced charge redistributions and their effects on the electrical contacts to WS2 monolayers

Abstract

The structural and electronic properties of high work function metal atoms (Au and Pd) and low work function metal atoms (Ti and In) adsorbed WS2 monolayers are systematically studied using first-principles calculations. Due to the weak interaction between Au and S atoms, high Schottky barriers may be formed at the interface. Using the metal Pd contact, p-type ohmic contact may be fabricated, but the localized and sparse partial charge densities decrease the electronic transparency and increase the contact resistance. For the low work function metal In, the delocalized n-type conduction interface states form in the bandgap; however, the wide and high electrostatic potential barrier suppresses the electron-transition probability. Strikingly different from Au, Pd, and In, the strongest interaction between Ti and S atoms induces the delocalized n-type conduction interface states with the highest electronic states near the Fermi level. The delocalized and high partial charge densities, as well as the narrowest and lowest electrostatic potential barrier, would enhance the electronic transparency and form the n-type ohmic contact. Furthermore, the results of the multilayer metal contacts are consistent with those of the atom-adsorbed systems. These investigations offer valuable resources for the design and fabrication of two-dimensional nanodevices.