Layer-Dependent Thermal Conductivity of Graphene toward Thermal Management Applications

Graphene has attracted considerable attention due to its exceptional thermal properties and potential applications in advanced thermal management systems. As the number of graphene layers increases, the cross-sectional area available for heat flow grows while the intrinsic in-plane thermal conductivity of each layer decreases because of enhanced interlayer scattering. The competing factors between the number of conducting channels and their interaction make understanding graphene's layer-dependent thermal conductivity essential for optimizing the thermal performance of graphene-based devices. In this study, the thermal conductivity of graphene with different layer numbers was measured by using a nanoscale thermal bridge method. Monolayer graphene exhibited a thermal conductivity up to 3100 W/m K, while the thermal conductivity further declined with layer number and stabilized beyond four layers. By evaluating the effective heat dissipation capability, a nonmonotonic dependence on graphene layer number was identified, with a critical regime appearing between 2 and 6 layers. The behavior was explained by a dual-path transport model, where both phononic and electronic heat carriers are considered. This layer-dependent reduction in thermal conductivity was attributed to phonon transport with an electronic heat-transport channel alongside. These findings provide insights into layer-dependent heat transfer in graphene and offer guidance for graphene-based thermal management and thermal design.