Significant reduction of graphene thermal conductivity by phononic crystal structure

We studied the thermal conductivity of graphene phononic crystal (GPnC), also named as graphene nanomesh, by molecular dynamics simulations. The dependence of thermal conductivity of GPnCs (κ_GPnC) on both length and temperature are investigated. It is found that the thermal conductivity of GPnCs is significantly lower than that of graphene (κ_G) and can be efficiently tuned by changing the porosity and period length. For example, the ratio κ_GPnC/κ_G can be changed from 0.1 to 0.01 when the porosity is changed from about 21% to 65%. It is also shown quantitatively that there are more states available for Umklapp three-phonon scatterings in GPnCs. The phonon participation ratio spectra reveal that more phonon modes are localized in GPnCs with larger porosity. Our results suggest that creating GPnCs is a valuable method to efficiently manipulate the thermal conductivity of graphene.