Observation of spontaneous high p-type doping on graphene-Talc heterostructure*

Graphene, an atomically thick layer of carbon atoms arranged in a hexagonal lattice, has attracted a lot of interest in basic and in applied physics. With the advent of h-BN crystals, it is possible to improve graphene device quality and uncover many interesting quantum effects of Dirac fermions. On the other hand, heterostructures prepared using other 2D materials do not lead to considerable improvements of graphene devices quality, but they allow the development of other non-linear electronics elements. Here we report that an atomically flat graphene-talc heterostructure is spontaneously p-type doped up to n ~ 2.2 x 10¹³ cm^-2 and show excellent charge mobility (~ 25,000 cm²V⁻¹s⁻¹). Raman investigation confirmed a preferential charge accumulation on graphene-talc rather than graphene on SiO₂. In addition to potentially improving solar cell efficiency, graphene doping via van der Waals stacking is also a promising route towards controlling the band gap opening in bilayer graphene, promoting a steady n or p type doping in graphene and, eventually, providing a new path to access superconducting states in graphene, predicted to exist only at very high doping.