Quasi-freestanding, striped WS₂ monolayer with an invariable band gap on Au(001)

Revealing the structural/electronic features and interfacial interactions of monolayer MoS₂ and WS₂ on metals is essential to evaluating the performance of related devices. In this study, we focused on the atomic-scale features of monolayer WS₂ on Au(001) synthesized via chemical vapor deposition. Scanning tunneling microscopy and spectroscopy reveal that the WS₂/Au(001) system exhibits a striped superstructure similar to that of MoS₂/Au(001) but weaker interfacial interactions, as evidenced by experimental and theoretical investigations. Specifically, the WS₂/Au(001) band gap exhibits a relatively intrinsic value of ∼2.0 eV. However, the band gap can gradually decrease to ∼1.5 eV when the sample annealing temperature increases from ∼370 to 720 °C. In addition, the doping level (or Fermi energy) of monolayer WS₂/Au(001) varies little over the valley and ridge regions of the striped patterns because of the homogenous distributions of point defects introduced by annealing. Briefly, this work provides an in-depth investigation into the interfacial interactions and electronic properties of monolayer MX₂ on metal substrates. [Figure not available: see fulltext.].