I am trying to understand how the sheet resistance would vary between a suspended sheet of graphene and a sheet of graphene on an insulating substrate (say SiO2). I am not looking for a law telling me how it varies, I just would like to understand if the sheet resistance increases when the graphene is bounded to an insulating substrate as I intuitively expext. And if yes, what is the physical reason? If you have any reference showing experimental measurements it would be appreciated (I haven't found anything so far).
Citing one of the original works on suspended graphene by Bolotin et al., scattering of charge carriers in substrate-supported graphene may result from a number of sources, including
[...] charged impurities on top of graphene or in the underlying substrate, corrugation of the graphene sheet, [...] or remote interfacial phonons in the substrate. The formation of electron and hole puddles can further contribute to scattering at low carrier density.
Which mechanism dominates may depend on the details of the setup.