Thermal Conductivity of Highly Anisotropic 2D Polymerized Fullerenes

2D polymerized fullerene sheets with weak van der Waals interfaces offer many advantages as future optoelectronic materials. To create the carbon allotrope studied in the work, magnesium is used as a dopant to create covalent bonds between fullerenes within a single plane. By locking rotation between fullerenes in the same sheet and losing a degree of motion, heat transfer is enhanced within the polymerized sheets, but remains low between the van der Waals bonded layers.

In this work, we measure the thermal conductivity of polymerized fullerenes using time-domain thermoreflectance (TDTR), an optical pump-probe technique for measuring thermal properties of thin films and nanostructures. We also present spatially resolved thermoreflectance maps of Mg₄C₆₀ and the resulting deintercalated (C60)_inf. Molecular dynamics simulations demonstrate extreme anisotropy in both the magnesium doped and deintercalated samples, and predict an average thermal conductivity significantly higher than that of a single-crystal fullerene, in agreement with experimental results.