Denser and taller carbon nanotube arrays on Cu foils useable as thermal interface materials

To achieve denser and taller carbon nanotube (CNT) arrays on Cu foils, catalyst and chemical vapor deposition (CVD) conditions were carefully engineered. CNTs were grown to similar to 50 mu m using Fe/TiN/Ta catalysts in which Ta and TiN acted as diffusion barriers for Cu and Ta, respectively. A tradeoff was found between the mass density and height of the CNT arrays, and CNT arrays with a mass density of 0.30 g cm(-3) and height of 45 mu m were achieved under optimized conditions. Thermal interface materials (TIMs) with CNT array/Cu foil/CNT array structures showed decreasing thermal resistance from 86 to 24 mm(2) K W-1 with increasing CNT array mass densities from 0.07-0.08 to 0.19-0.26 g cm(-3) for Cu and Al blocks with surfaces as rough as 20-30 mu m. The best CNT/Cu/CNT TIMs showed thermal resistance values comparable to that of a typical indium sheet TIM. (C) 2015 The Japan Society of Applied Physics