Sabina's paper online (Small 2018)
Layer-by-layer decoupling of twisted graphene sheets epitaxially grown on a metal substrate
S. Simon, E. Voloshina, J. Tesch, F. Förschner, V. Enenkel, Ch. Herbig, T. Knispel, A. Tries, J. Kröger, Yu. Dedkov, and M. Fonin
The electronic properties of graphene can be efficiently altered upon interaction with the underlying substrate resulting in a dramatic change of charge carrier behavior. Here we investigate the evolution of the local electronic properties of epitaxial graphene on a metal upon the controlled formation of multilayers, which are produced by intercalation of atomic carbon in graphene/Ir(111). Using scanning tunneling microscopy and Landau level spectroscopy, we show that for a monolayer and bilayers with small-angle rotations Landau levels are fully suppressed, indicating that the metal-graphene interaction is largely confined to the first graphene layer. Bilayers with large twist angles as well as twisted trilayers demonstrate a sequence of pronounced Landau levels characteristic for a free-standing graphene monolayer pointing towards an effective decoupling of the top layer from the metal substrate. Our findings give evidence for the controlled preparation of epitaxial graphene multilayers with different degree of decoupling, which represent an ideal platform for future electronic and spintronic applications.