Thermal transport barrier in carbon nanotube array nano-thermal interface materials

Abstract

Although carbon nanotubes (CNTs) could theoretically achieve thermal conductivity (kCNT) as high as 100 W/m K, the nature of height non-uniformity could induce enormous thermal contact resistance at CNT array-heat sink interface (Rc), obscuring the quality of CNT arrays compared to commercial nano-thermal interface materials (nTIMs). Direct and experimental extraction of the effect of array height uniformity for thermal transport, Rc, provides a foundation for developing an optimum preparation approach of CNT array-based nTIM. However, this remains a big challenge for even the state-of-the-art interface thermophysical measurement techniques. To remedy this situation, we developed a method for achieving experimental distinction between kCNT and Rc. By focusing on growing CNT arrays with height uniformity, instead of the typical method of focusing on increasing the kCNT, we realized the performance boost by eightfold increase in uniformity and elimination of carbonaceous byproducts on the array canopy and dispersed Fe within walls. Rc is successfully cut down by 60% to 1.7 × 10−5 m2 K/W, while maintaining extremely high kCNT ∼170 W/m K is maintained allowing for fast heat transport within CNTs. This study presents novel quantitative evidence that lowering Rc is the most efficient for thermal transport enhancement for CNT array nTIMs.