Thermal conductivity of graphene with defects induced by electron beam irradiation

We investigate the thermal conductivity of suspended graphene as a function of the density of defects, ND, introduced in a controllable way. High-quality graphene layers are synthesized using chemical vapor deposition, transferred onto a transmission electron microscopy grid, and suspended over similar to 7.5 mu m size square holes. Defects are induced by irradiation of graphene with the low-energy electron beam (20 keV) and quantified by the Raman D-to-G peak intensity ratio. As the defect density changes from 2.0 x 10(10) cm(-2) to 1.8 x 10(11) cm(-2) the thermal conductivity decreases from similar to(1.8 +/- 0.2) x 10(3) W mK(-1) to similar to(4.0 +/- 0.2) x 10(2) W mK(-1) near room temperature. At higher defect densities, the thermal conductivity reveals an intriguing saturation-type behavior at a relatively high value of similar to 400 W mK(-1). The thermal conductivity dependence on the defect density is analyzed using the Boltzmann transport equation and molecular dynamics simulations. The results are important for understanding phonon-point defect scattering in two-dimensional systems and for practical applications of graphene in thermal management.