Low-resistance ohmic contacts are a challenge for electronic devices based on two-dimensional materials. We show that an atomically precise junction between a two-dimensional semiconductor and a metallic contact can lead to a semiconductor-to-metal transition in the two-dimensional material--a finding which points the way to a possible method of achieving low-resistance junctions. Specifically, single-layer WS2 undergoes a semiconductor-to-metal transition when epitaxially grown on Ag(111), while it remains a direct band gap semiconductor on Au(111). The metallicity of the single layer on Ag(111) is established by lineshape analysis of core level photoemission spectra. Angle-resolved photoemission spectroscopy locates the metallic states near the Q point of the WS2 Brillouin zone. Density functional theory calculations show that the metallic states arise from hybridization between Ag bulk bands and the local conduction band minimum of WS2 near the Q point.
@article{arxiv.1708.02799,
title = {Contact-Induced Semiconductor-to-Metal Transition in Single-Layer WS$_2$},
author = {Maciej Dendzik and Albert Bruix and Matteo Michiardi and Arlette S. Ngankeu and Marco Bianchi and Jill A. Miwa and Bjørk Hammer and Philip Hofmann and Charlotte E. Sanders},
journal= {arXiv preprint arXiv:1708.02799},
year = {2018}
}