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MRS Advances © 2017 Materials Research Society DOI: 10.1557/adv.2017.555

Synthesis and Thermal Analysis of Vertically Aligned CNTs Grown on Copper Substrates Qiuhong Zhanga, Levi Elstonb a. University of Dayton Research Institute (UDRI), Dayton, OH 45469, USA b. Air Force Research Laboratory (AFRL), WPAFB, OH 45433, USA Due to the low degree of contact area and weak interfacial adhesion between CNTs and the growth substrate (Cu), large thermal contact resistance is the largest challenge preventing the use of vertically aligned CNTs (VACNTs) as a thermal interface material (TIM). Although significant research has been done regarding the growth of CNTs on reactive substrates by using an appropriate buffer layer in this group’s previous work, there are many unanswered questions associated with using VACNTs as a thermal interface material beyond synthesis. This effort extends prior work on carbon nanotube growth, by concentrating on ways to evaluate/measure CNT-based nanocomposite thermal resistance. In this study, with the use of a laser flash measurement system, the influence of CNT array properties (layer height and density) on the thermal diffusivity and thermal resistance of the CNT composite were investigated. Test results identify a correlation between the CNT array density/thickness and its thermal resistance. 1. Introduction Thermal management has become a very important issue in recent years for improving device reliability and performance as the size of the integrated circuits decrease and the power density becomes higher. To address this significant thermal management problem, a key role is developing improved thermal interface materials (TIMs). The main problems with current TIMs include: fatigue failure (solder), low thermal conductivity (phase change materials), and dryout/pump-out (grease). These TIM weaknesses have lead researchers to develop advanced nanoengineered materials to make more efficient thermal interfaces with low thermal resistance and good compliance. Among the many nano-materials available, carbon nanotubes (CNTs), with their unique thermal, electrical, and mechanical properties, are a very attractive candidate for advanced TIMs and have been widely investigated by many groups with various techniques [15]. Compared to an individual CNT, the CNT array have shown a much lower (with extreme variation) reported value for thermal conductivity (0.3-83w/m-k) [6-8]. This significant degradation is due to VACNTs small volume fraction and phonon scattering caused by defects and inter-tube contacts [9]. The CNT array density and structure/morphology, which is determined by the synthesis method and growth substrate of CNTs, will play a key role on their performance. Therefore, using the proper approach to evaluate thermal properties of CNT array (made under certain condition and substrate) is very important for properly designing applications of CNTs as TIMs and CNT based thermal conductive composites. So far, very little has been studied with regard to the interfacial thermal properties of CNTs gr