Anomalous thermal transport behavior in graphene-like carbon nitride (C3N)

Abstract

The success of graphene created a new era in materials science, especially for two-dimensional (2D) materials. 2D single-crystal carbon nitride (C₃N) is the first and only crystalline, hole-free, single-layer carbon nitride and its controlled large-scale synthesis has recently attracted tremendous interest in thermal transport. Here, we performed a comparative study of thermal transport between monolayer C₃N and the parent graphene, and focused on the effect of temperature and strain on the thermal conductivity (κ) of C₃N, by solving the phonon Boltzmann transport equation (BTE) based on first-principles calculations. The κ of C₃N shows an anomalous temperature dependence, and the κ of C₃N at high temperatures is larger than the expected value following the common trend of κ ∼ 1/T. Moreover, the κ of C₃N is found to be increased by applying a bilateral tensile strain, despite its similar planar honeycomb structure to graphene. The underlying mechanism is revealed by providing direct evidence for the interaction between lone-pair N-s electrons and bonding electrons from C atoms in C₃N based on the analysis of orbital-projected electronic structures and electron localization function (ELF). Our research not only conduct a comprehensive study on the thermal transport in graphene-like C₃N, but also reveal the physical origin of its anomalous properties, which would have significant implications on the future studies of nanoscale thermal transport.