Transmittance of monolayer graphene film obtained with visible-absorption spectroscopy on quartz substrate. The transmittance of graphene film was measured at 550 nm. (b) Low-resolution TEM image showing monolayer graphene film suspended on a TEM grid. (c) SAED pattern of the graphene film owning only one set of diffraction pattern. (d) HRTEM image of monolayer graphene edges that show one carbon layer