Thermal Properties of Metal-Coated Vertically Aligned Single-Wall Nanotube Arrays

Abstract

Owing to their high thermal conductivities, carbon nanotubes (CNTs) are promising for use in advanced thermal interface materials. While there has been much previous research on the properties of isolated CNTs, there are few thermal data for aligned films of single wall nanotubes. Furthermore, such data for nanotube films do not separate volume from interface thermal resistances. This paper uses a thermoreflectance technique to measure the volumetric heat capacity and thermal interface resistance and to place a lower bound on the internal volume resistance of a vertically aligned single wall CNT array capped with an aluminum film and palladium adhesion layer. The total thermal resistance of the structure, including volume and interface contributions, is 12m2KMW−1. The data show that the top and bottom interfaces of the CNT array strongly reduce its effective vertical thermal conductivity. A low measured value for the effective volumetric heat capacity of the CNT array shows that only a small volume fraction of the CNTs participate in thermal transport by bridging the two interfaces. A thermal model of transport in the array exploits the volumetric heat capacity to extract an individual CNT-metal contact resistance of 10m2K1GW−1 (based on the annular area Aa=πdb), which is equivalent to the volume resistance of 14nm of thermal SiO2. This work strongly indicates that increasing the fraction of CNT-metal contacts can reduce the total thermal resistance below 1m2KMW−1.

Nanowire-Polymer Nanocomposites as Thermal Interface Material

“…The deposited Au film effectively connected most of the nanowires together and thereby increased the effective contact area. As a result, the thermal impedance decreased, which was also reported for carbon nanotube arrays (Panzer et al 2008;Wu et al 2005). This limiting of contact area (without top metal layer) leads to an increase in the contact impedance, ultimately increasing the overall impedance of the TIM.…”

Thermal Conductance of Buckled Carbon Nanotubes

“…While the reports of high thermal conductivity have motivated applications of carbon nanotubes as thermal interface materials [4][5][6][7][8] and additives in nanocomposites [9][10][11][12], in practice, one needs to consider various thermal resistances that manifest in the actual samples and environments. In this course, influence of impurities and defects on SWNT heat conduction has been widely explored [13][14][15][16][17][18].…”

Toward Plasmonic UC-PBG Structures based SWCNTs for Optoelectronics Applications

“…Therefore, to achieve more uniform SWCNTs dispersion in array forms and get the advantage of their ballistic properties at the individual ones, vertically aligned forests are subjected to the research [9][10][11][12]. In [9], electron beam evaporation on a thermal oxide layer of silicon substrate is used to grow the SWCNTs vertically with the aid of chemical vapor deposition plasma system. A controlled atomic diffusion-induced catalyst evolution on an aluminum thin-film substrate was introduced in [10] to grow vertically aligned carbon nanotube arrays by a conventional low-pressure thermal chemical vapor deposition.…”

“…However, most of these techniques reduce the real advancements in the electromagnetic properties of the SWCNTs when they are treated as bulk films not as ballistic conductors [1]. Therefore, to achieve more uniform SWCNTs dispersion in array forms and get the advantage of their ballistic properties at the individual ones, vertically aligned forests are subjected to the research [9][10][11][12]. In [9], electron beam evaporation on a thermal oxide layer of silicon substrate is used to grow the SWCNTs vertically with the aid of chemical vapor deposition plasma system.…”