Thermal transport of monolayer amorphous carbon and boron nitride

Abstract

Amorphous materials feature localization of electrons and phonons that alter the electronic, mechanical, thermal, and magnetic properties. Here, we report calculations of the in-plane thermal conductivities of monolayer amorphous carbon and monolayer amorphous boron nitride, by reverse nonequilibrium molecular dynamics simulations. We find that the thermal conductivities of both monolayer amorphous carbon (MAC) and monolayer amorphous boron nitride (ma-BN) are about two orders of magnitude smaller than their crystalline counterparts. Moreover, the ultralow thermal conductivities are independent of the temperature and strain due to their extremely short heat carrier mean free paths. The relation between the structure disorder and the reduction of the thermal conductivity is analyzed in terms of the vibrational density of states and the participation ratio. The ma-BN shows strong vibrational localization across the frequency range, while the MAC exhibits a unique extended G* diffuson mode due to its sp2 hybridization and the broken E2g symmetry. The irregular vibrational patterns are also analyzed. The present results may enable potential applications of MAC and ma-BN in thermal management.