Width dependent intrinsic thermal conductivity of suspended monolayer graphene

Size dependence is one of the most important unique features of thermal conductivity in two-dimensional materials. Suspended single-layer graphene (SLG) provides a perfect platform for studying the size dependent phonon transport. Here we report measurement and theoretical analysis of heat conduction in suspended SLG as a function of width and temperature. The thermal conductivity of graphene was larger for wider SLG. This width effect was smaller at higher temperatures. In suspended SLG, the long wave-length phonons tend to be more scattered at the lateral boundaries of narrow SLG ribbon, in which the mean free path of phonons is close to the sample width. This behavior can be understood as a mode selectivity of phonon-boundary scattering for suspended SLG. The result revealed the unique width dependence of thermal conductivity in suspended SLG and provided useful guidelines for the future SLG-based thermal applications.