Thermal interfaces based on vertically aligned carbon nanotubes : An analysis of the different contributions to the overall thermal resistance

In this paper, we will present and discuss our results on the thermal interface resistances of the thermal interface materials based on vertically aligned carbon nanotubes. In this system, the total interface resistance is the sum of thermal resistances created by the contact between the growth surface and the CNTs, the intrinsic resistance of the CNTs array, and the contact between the loose end of the CNTs and the opposite substrate. The latter is reported to be the limiting factor in the optimization of the global interface resistance. We present here thermal resistances measurements of multilayered VACNT samples. In particular, the resitances obtained with a heated polymer film as an adhesive layer at the CNT/superstrate interface are compared with the direct CNT/superstrate contact. It is shown that the use of a polymer as interface material, despite its low thermal conductivity, leads to an improvement of the total thermal resistance. The CNT length dependant resistance measurements allow the extraction of the CNT turf thermal conductivity as well as the contact resistances. Finally, the origin of the improvement is discussed using these results.