Carrier scattering, mobilities, and electrostatic potential in monolayer, bilayer, and trilayer graphene

The carrier density and temperature dependence of the Hall mobility in monolayer, bilayer, and trilayer graphene has been systematically studied. We found that as the carrier density increases, the mobility decreases for monolayer graphene, while it increases for bilayer/trilayer graphene. This can be explained by the different density of states in monolayer and bilayer/trilayer graphenes. In monolayer, the mobility also decreases with increasing temperature primarily due to substrate surface polar phonon scattering. In bilayer/trilayer graphene, on the other hand, the mobility increases with temperature because the electric field of the substrate surface polar phonons is effectively screened by the additional graphene layer(s) and the mobility is dominated by Coulomb scattering. We also find that the temperature dependence of the Hall coefficient in monolayer, bilayer, and trilayer graphene can be explained by the formation of electron and hole puddles in graphene. This model also explains the temperature dependence of the minimum conductance of monolayer, bilayer, and trilayer graphene. The electrostatic potential variations across the different graphene samples are extracted.