Aligned carbon-doping to modulate thermal and electrical conductivity of boron carbon nitride grown from chemical vapor deposition

Abstract

Hexagonal boron carbon nitride (hBCN) thin films with a wide range of carbon doping are synthesized in a chemical vapor deposition (CVD) process by varying 3 distinct precursors. Utilizing the optothermal method, the highest thermal conductivities of hBCN thin films is measured experimentally as 836 ± 312 W/m·K, for the hBCN with the highest carbon doping, surpassing the measured hexagonal boron nitride (hBN) conductivity of 462 ± 158 W/m·K. Moreover, we demonstrate that the electrical conductivity retains the insulative properties of hBN with lower carbon doping levels. Additionally, insights of how increasing amounts of carbon increase the conductivity by forming graphene like channels integrated into the hBN networks have been examined by molecular dynamics simulations. These simulations confirm a greater increase in high frequency phonon group velocities contribute to higher thermal conductivity, when aligning carbon rather than simply increasing the quantity of carbon. The aligned carbon channels are effective in overcoming the additional phonon scattering, that occurs especially in the LA mode, when adding carbon to the hBN network. By varying the carbon doping to maximize the thermal conductivity while minimizing the electrical conductivity, we have discovered an effective method of producing optimized hBCN thin films, which are ideal to be utilized in thermal interface material applications as a lower cost alternative to hBN.