▎ 摘　　要

It has been argued that the electron-hole puddles formed on graphene are mostly due to substrate-induced charged impurities [J. Martin et al., Nature Phys. 4, 144 (2008), Y. Zhang et al., Nature Phys. 5, 722 (2009)]. Here, using first-principles ab initio calculations, we show that the existence of ripples and electron-hole puddles is indeed an intrinsic property of graphene at finite temperatures. We found a relatively large correlation between the electronic charge density distribution on the surface of graphene and its local geometrical properties, such as local mean curvature and average bond length. We show that the electron and hole puddles appear in places where curvatures are large and small, respectively. We also determined the average sizes of the observed electron-hole puddles and have reported their percolating nature.