▎ 摘　　要

The resistivity of ultraclean suspended graphene is strongly temperature (T) dependent for 5 < T < 240 K. At T similar to 5 K transport is near-ballistic in a device of similar to 2 Am dimension and a mobility similar to 170 000 cm(2)/V s. At large carrier density, n > 0.5 X 10(11) cm(-2), the resistivity increases with increasing T and is linear above 50 K, suggesting carrier scattering from acoustic phonons. At T = 240 K the mobility is similar to 120000 cm(2)/V s, higher than in any known semiconductor. At the charge neutral point we observe a nonuniversal conductivity that decreases with decreasing T, consistent with a density inhomogeneity < 108 cm(-2).