▎ 摘　　要

We report on the temperature dependent electron transport in graphene at different carrier densities n. Employing an electrolytic gate, we demonstrate that n can be adjusted up to 4 X 10(14) cm(-2) for both electrons and holes. The measured sample resistivity rho increases linearly with temperature T in the high temperature limit, indicating that a quasiclassical phonon distribution is responsible for the electron scattering. As T decreases, the resistivity decreases more rapidly following rho(T) similar to T-4. This low temperature behavior can be described by a Bloch-Gruneisen model taking into account the quantum distribution of the two-dimensional acoustic phonons in graphene. We map out the density dependence of the characteristic temperature Theta(BG) defining the crossover between the two distinct regimes, and show that, for all n, rho(T) scales as a universal function of the normalized temperature T/Theta(BG).