  Large-area and high-quality single-layer transition metal dichalcogenides can
be synthesized by epitaxial growth on single-crystal substrates. An important
advantage of this approach is that the interaction between the single-layer and
the substrate can be strong enough to enforce a single crystalline orientation
of the layer. On the other hand, the same interaction can lead to hybridization
effects, resulting in the deterioration of the single-layer's native
properties. This dilemma can potentially be solved by decoupling the
single-layer from the substrate surface after the growth via intercalation of
atoms or molecules. Here we show that such a decoupling can indeed be achieved
for single-layer WS2 epitaxially grown on Ag(111) by intercalation of Bi atoms.
This process leads to a suppression of the single-layer WS2-Ag substrate
interaction, yielding an electronic band structure reminiscent of free-standing
single-layer WS2.
