Thermal conductivity of diamond-like carbon films

The authors report the thermal conductivity (K) of a variety of carbon films ranging from polymeric hydrogenated amorphous carbons (a-C:H) to tetrahedral amorphous carbon (ta-C). The measurements are performed using the 3ω method. They show that thermal conduction is governed by the amount and structural disorder of the sp3 phase. If the sp3 phase is amorphous, K scales linearly with the C–C sp3 content, density, and elastic constants. Polymeric and graphitic films have the lowest K (0.2–0.3W∕mK), hydrogenated ta-C:H has K∼1W∕mK, and ta-C has the highest K (3.5W∕mK). If the sp3 phase orders, even in small grains such as in micro- or nanodiamond, a strong K increase occurs for a given density, Young’s modulus, and sp3 content.