Figure 1. Assembly and precharacterization of heterostructures.

(a) Monolayer graphene flakes produced on oxygen plasma-treated SiO₂. Inset (white square): typical graphene flake size on non-plasma-treated SiO₂. To scale with (a). (b) Graphene Raman 2D peak dependence on substrate – the Raman I(2D)/I(G) ratio increases for graphene picked up with hBN from SiO₂ irrespective of the oxygen plasma pre-treatment of the substrate. (c) Micromanipulator with slide assembly used for assembly of heterostructures. (d,e) Polymer stack on glass slide used for pick-up and drop-down. (f) Schematic process flow for assembly of 2D heterostructures by pick-up and drop-down.