Photoacoustic characterization of carbon nanotube array thermal interfaces

Abstract

Thermal conductivity of nanocrystalline silicon by direct molecular dynamics simulation J. Appl. Phys. 112, 064305 (2012) Electrical and heat conduction mechanisms of GeTe alloy for phase change memory application J. Appl. Phys. 112, 053712 (2012) Thermal rectification and phonon scattering in silicon nanofilm with cone cavity J. Appl. Phys. 112, 054312 (2012) Analysis of the "3-Omega" method for substrates and thick films of anisotropic thermal conductivity This work describes an experimental study of thermal conductance across multiwalled carbon nanotube ͑CNT͒ array interfaces, one sided ͑Si-CNT-Ag͒ and two sided ͑Si-CNT-CNT-Cu͒, using a photoacoustic technique ͑PA͒. Well-anchored, dense, and vertically oriented multiwalled CNT arrays have been directly synthesized on Si wafers and pure Cu sheets using plasma-enhanced chemical vapor deposition. With the PA technique, the small interface resistances of the highly conductive CNT interfaces can be measured with accuracy and precision. In addition, the PA technique can resolve the one-sided CNT interface component resistances ͑Si-CNT and CNT-Ag͒ and the two-sided CNT interface component resistances ͑Si-CNT, CNT-CNT, and CNT-Cu͒ and can estimate the thermal diffusivity of the CNT layers. The thermal contact resistances of the one-and two-sided CNT interfaces measured using the PA technique are 15.8± 0.9 and 4.0± 0.4 mm 2 K/W, respectively, at moderate pressure. These results compare favorably with those obtained using a steady state, one-dimensional reference bar method; however, the uncertainty range is much narrower. The one-sided CNT thermal interface resistance is dominated by the resistance between the free CNT array tips and their opposing substrate ͑CNT-Ag͒, which is measured to be 14.0± 0.9 mm 2 K / W. The two-sided CNT thermal interface resistance is dominated by the resistance between the free tips of the mating CNT arrays ͑CNT-CNT͒, which is estimated to be 2.1± 0.4 mm 2 K/W.

Electrothermal Bonding of Carbon Nanotubes to Glass

“…Son et al 7 conducted photothermoelectric measurements on CNT-Si/SiO 2 growth interfaces and found the interfacial resistance to be significantly higher than the predictions of Prasher 6 , but explained this discrepancy as arising from mechanical imperfections and the presence of growth catalyst in the experiments that were not accounted for in the idealized model. Cola et al 8 studied thermal contact resistance between vertically oriented carbon nanotube arrays contacting silver surfaces experimentally and demonstrated that the free nanotube tip resistance dominated the overall resistance within the stack of resistances between the growth substrate and the contacting metal ( Figure 1a). …”

Carbon Nanotube Array Thermal Interfaces for High-Temperature Silicon Carbide Devices

“…The opportunity to reduce interfacial thermal inefficiencies through the use of CNT arrays considered herein would substantially enhance their reliability and utility. Previous studies [7][8][9][10][11][12][13][14][15][16] have demonstrated that multiwalled carbon nanotube (MWCNT) arrays grown on one side of an interface can achieve room-temperature thermal resistances as low as 7-25 mm 2 K/W, depending on the method of fabrication and array morphology. Using transient optical techniques, Wang et al [11], Cola et al [13], and Tong et al [14] revealed that the interfaces between MWCNTs and their growth substrate and the interfaces established at the free ends of MWCNTs can be significant thermal bottlenecks in MWCNT array interfaces.…”

Recent Advances in Vapor Chamber Transport Characterization for High-Heat-Flux Applications

“…The intrinsically high thermal conductivity of CNTs determined both theoretically [193,194] and experimentally [195][196][197][198] may be exploited, and has previously led to a reduction in the resistance to heat flow at interfaces between components [199][200][201][202] and a development of novel composite materials with increased thermal conductivity [202][203][204]. The pores of nanowire arrays also have a high capillary pressure; however, their relative impermeability compared to microscale wick structures must be carefully assessed in the design process.…”