Transport Phenomena in Artificial Graphene Polytypes

The stacking order (polytypes) of graphene multi-layers in mechanically exfoliated flakes is naturally dictated by energetically favorable considerations, a polytype with the higher symmetry is found more in comparison to one which has lower symmetry.<br/>As a case study tetra-layer graphene is known to have three distinguishable polytypes, Bernal, Rhombohedral, and an intermediate polytype namely Polar. ABAB, ABCA, and ABCB stacking accordingly. While Bernal and Rhombohedral are considered stable the polar state is found much less in mechanically exfoliated graphene. Furthermore, during device fabrication the initial polytype may change to another, a more stable one, preventing the study of transport properties in unique polytypes.<br/>In this study, by careful design of the heterostructure stacking of vdW materials, artificial polytypes are made and stabilized. Allowing the study of more than a single polytype in a single device. Such capabilities allow a broader understanding of the transport properties in a single multi-layer graphene switchable device.