  We report on a scanning confocal Raman spectroscopy study investigating the
strain-uniformity and the overall strain and doping of high-quality chemical
vapour deposited (CVD) graphene-based heterostuctures on a large number of
different substrate materials, including hexagonal boron nitride (hBN),
transition metal dichalcogenides, silicon, different oxides and nitrides, as
well as polymers. By applying a hBN-assisted, contamination free, dry transfer
process for CVD graphene, high-quality heterostructures with low doping
densities and low strain variations are assembled. The Raman spectra of these
pristine heterostructures are sensitive to substrate-induced doping and strain
variations and are thus used to probe the suitability of the substrate material
for potential high-quality graphene devices. We find that the flatness of the
substrate material is a key figure for gaining, or preserving high-quality
graphene.
