Dense Vertically Aligned Multiwalled Carbon Nanotube Arrays as Thermal Interface Materials
02 Apr 2007-IEEE Transactions on Components and Packaging Technologies (IEEE)-Vol. 30, Iss: 1, pp 92-100
TL;DR: In this article, a phase sensitive transient thermo-reflectance technique was used to measure the thermal conductance of the two interfaces on each side of a vertically aligned carbon nanotube array as well as the CNT array itself.
Abstract: Carbon nanotube (CNT) arrays are being considered as thermal interface materials (TIMs). Using a phase sensitive transient thermo-reflectance technique, we measure the thermal conductance of the two interfaces on each side of a vertically aligned CNT array as well as the CNT array itself. We show that the physically bonded interface by van der Waals adhesion has a conductance ~105W/m2K and is the dominant resistance. We also demonstrate that by bonding the free-end CNT tips to a target surface with the help of a thin layer of indium weld, the conductance can be increased to ~106W/m2K making it attractive as a TIM
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TL;DR: The impact of CNT density on thermal conduction considering boundary resistances, increased defect concentrations, and the possibility of suppressed phonon modes in the CNTs is discussed.
Abstract: Nanostructured composites containing aligned carbon nanotubes (CNTs) are very promising as interface materials for electronic systems and thermoelectric power generators. We report the first data for the thermal conductivity of densified, aligned multiwall CNT nanocomposite films for a range of CNT volume fractions. A 1 vol % CNT composite more than doubles the thermal conductivity of the base polymer. Denser arrays (17 vol % CNTs) enhance the thermal conductivity by as much as a factor of 18 and there is a nonlinear trend with CNT volume fraction. This article discusses the impact of CNT density on thermal conduction considering boundary resistances, increased defect concentrations, and the possibility of suppressed phonon modes in the CNTs.
459 citations
TL;DR: In this paper, the state-of-the-art of carbon-based nanomaterials, particularly the one-dimensional (1-D) forms, carbon nanotubes (CNTs) and graphene nanoribbons (GNRs), are reviewed.
Abstract: This paper reviews the current state of research in carbon-based nanomaterials, particularly the one-dimensional (1-D) forms, carbon nanotubes (CNTs) and graphene nanoribbons (GNRs), whose promising electrical, thermal, and mechanical properties make them attractive candidates for next-generation integrated circuit (IC) applications. After summarizing the basic physics of these materials, the state of the art of their interconnect-related fabrication and modeling efforts is reviewed. Both electrical and thermal modeling and performance analysis for various CNT- and GNR-based interconnects are presented and compared with conventional interconnect materials to provide guidelines for their prospective applications. It is shown that single-walled, double-walled, and multiwalled CNTs can provide better performance than that of Cu. However, in order to make GNR interconnects comparable with Cu or CNT interconnects, both intercalation doping and high edge-specularity must be achieved. Thermal analysis of CNTs shows significant advantages in tall vias, indicating their promising application as through-silicon vias in 3-D ICs. In addition to on-chip interconnects, various applications exploiting the low-dimensional properties of these nanomaterials are discussed. These include chip-to-packaging interconnects as well as passive devices for future generations of IC technology. Specifically, the small form factor of CNTs and reduced skin effect in CNT interconnects have significant implications for the design of on-chip capacitors and inductors, respectively.
411 citations
Cites methods from "Dense Vertically Aligned Multiwalle..."
...using CNT as thermal interface materials (TIMs) for packaging [148], [149] and have demonstrated that CNTs can provide lower thermal resistance....
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TL;DR: In this paper, a detailed review of heat conduction research on both individual carbon nanotubes and nanostructured films consisting of arrays or disordered nanotube mats is presented.
Abstract: The extremely high thermal conductivities of carbon nanotubes have motivated a wealth of research. Progress includes innovative conduction metrology based on microfabricated platforms and scanning thermal probes as well as simulations exploring phonon dispersion and scattering using both transport theory and molecular dynamics. This article highlights these advancements as part of a detailed review of heat conduction research on both individual carbon nanotubes and nanostructured films consisting of arrays of nanotubes or disordered nanotube mats. Nanotube length, diameter, and chirality strongly influence the thermal conductivities of individual nanotubes and the transition from primarily diffusive to ballistic heat transport with decreasing temperature. A key experimental challenge, for both individual nanotubes and aligned films, is the separation of intrinsic and contact resistances. Molecular dynamics simulations have studied the impacts of specific types of imperfections on the nanotube conductance and its variation with length and chirality. While the properties of aligned films fall short of predictions based on individual nanotube data, improvements in surface engagement and postfabrication nanotube quality are promising for a variety of applications including mechanically compliant thermal contacts.
379 citations
Cites background from "Dense Vertically Aligned Multiwalle..."
...The thermal diffusivity and thermal conductivity in aligned CNT arrays is highly anisotropic, such that the axial thermal conductivity is as much as 110 times greater than the radial conductivity (Borca-Tasciuc et al., 2005; Ivanov et al., 2006; Tong et al., 2006, 2007; Son et al., 2008)....
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...These effects could explain why the short nanotubes (L < 10 m) of Tong et al. (2006, 2007) showed high film thermal conductivities, with the extracted individual nanotube thermal conductivity as high as 2650 Wm 1 K 1....
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...The high thermal conductivity (exceeding 250 Wm 1 K 1 at 10% volume fraction CNTs) reported by Tong et al. (2006, 2007) shows promise for fabricating vertically aligned CNT arrays which take full advantage of the high thermal conductivity reported for individual CNTs....
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...These include indium solder (Tong et al., 2006, 2007), palladium thiolate (Hodson et al., 2011), electrothermal (Aradhya, Garimella, and Fisher, 2008), and thermocompression (Johnson et al., 2009; Cross et al., 2010; Hamdan et al., 2010) bonding techniques, all of which have shown significant…...
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...Effective thermal conductivities of vertically aligned CNT arrays reported in the literature span a large range from 0:145 Wm 1 K 1 (Wang, Zhong, and Xu, 2005) to 267 Wm 1 K 1 (Tong et al., 2006, 2007)....
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Wright-Patterson Air Force Base1, Vanderbilt University2, University of Manchester3, University of Cambridge4, Lawrence Livermore National Laboratory5, University of Southern California6, Massachusetts Institute of Technology7, Kansas State University8, Yale University9, Rice University10, Texas A&M University11, Aix-Marseille University12, National Institute of Advanced Industrial Science and Technology13, Waseda University14, National Research Council15, Aalto University16, University of Wisconsin-Madison17, Georgia Institute of Technology18, Tsinghua University19, Brookhaven National Laboratory20, University of Pennsylvania21, Peking University22, Pennsylvania State University23, Oak Ridge National Laboratory24, University of Tokyo25
TL;DR: While the primary focus of this review is on the science framework of SWCNT growth, connections to mechanisms underlying the synthesis of other 1D and 2D materials such as boron nitride nanotubes and graphene are drawn.
Abstract: Advances in the synthesis and scalable manufacturing of single-walled carbon nanotubes (SWCNTs) remain critical to realizing many important commercial applications. Here we review recent breakthroughs in the synthesis of SWCNTs and highlight key ongoing research areas and challenges. A few key applications that capitalize on the properties of SWCNTs are also reviewed with respect to the recent synthesis breakthroughs and ways in which synthesis science can enable advances in these applications. While the primary focus of this review is on the science framework of SWCNT growth, we draw connections to mechanisms underlying the synthesis of other 1D and 2D materials such as boron nitride nanotubes and graphene.
354 citations
TL;DR: At a very low solid concentration, the room-temperature thermal conductivity of freestanding graphene-based foams (GF), comprised of few-layer graphene and ultrathin graphite synthesized through the use of methane chemical vapor deposition on reticulated nickel foams, was increased, revealing the benefit of eliminating internal contact thermal resistance in the continuous GF structure.
Abstract: At a very low solid concentration of 0.45±0.09 vol %, the room-temperature thermal conductivity (κGF) of freestanding graphene-based foams (GF), comprised of few-layer graphene (FLG) and ultrathin graphite (UG) synthesized through the use of methane chemical vapor deposition on reticulated nickel foams, was increased from 0.26 to 1.7 W m–1 K–1 after the etchant for the sacrificial nickel support was changed from an aggressive hydrochloric acid solution to a slow ammonium persulfate etchant. In addition, κGF showed a quadratic dependence on temperature between 11 and 75 K and peaked at about 150 K, where the solid thermal conductivity (κG) of the FLG and UG constituents reached about 1600 W m–1 K–1, revealing the benefit of eliminating internal contact thermal resistance in the continuous GF structure.
323 citations
References
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NEC1
TL;DR: Iijima et al. as mentioned in this paper reported the preparation of a new type of finite carbon structure consisting of needle-like tubes, which were produced using an arc-discharge evaporation method similar to that used for fullerene synthesis.
Abstract: THE synthesis of molecular carbon structures in the form of C60 and other fullerenes1 has stimulated intense interest in the structures accessible to graphitic carbon sheets. Here I report the preparation of a new type of finite carbon structure consisting of needle-like tubes. Produced using an arc-discharge evaporation method similar to that used for fullerene synthesis, the needles grow at the negative end of the electrode used for the arc discharge. Electron microscopy reveals that each needle comprises coaxial tubes of graphitic sheets, ranging in number from 2 up to about 50. On each tube the carbon-atom hexagons are arranged in a helical fashion about the needle axis. The helical pitch varies from needle to needle and from tube to tube within a single needle. It appears that this helical structure may aid the growth process. The formation of these needles, ranging from a few to a few tens of nanometres in diameter, suggests that engineering of carbon structures should be possible on scales considerably greater than those relevant to the fullerenes. On 7 November 1991, Sumio Iijima announced in Nature the preparation of nanometre-size, needle-like tubes of carbon — now familiar as 'nanotubes'. Used in microelectronic circuitry and microscopy, and as a tool to test quantum mechanics and model biological systems, nanotubes seem to have unlimited potential.
39,086 citations
"Dense Vertically Aligned Multiwalle..." refers background in this paper
...Iijima [4], have been predicted to have very high thermal con-...
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Book•
31 Dec 1959
TL;DR: In this paper, a classic account describes the known exact solutions of problems of heat flow, with detailed discussion of all the most important boundary value problems, including boundary value maximization.
Abstract: This classic account describes the known exact solutions of problems of heat flow, with detailed discussion of all the most important boundary value problems.
21,807 citations
TL;DR: The thermal conductivity and thermoelectric power of a single carbon nanotube were measured using a microfabricated suspended device and shows linear temperature dependence with a value of 80 microV/K at room temperature.
Abstract: The thermal conductivity and thermoelectric power of a single carbon nanotube were measured using a microfabricated suspended device. The observed thermal conductivity is more than 3000 W/K m at room temperature, which is 2 orders of magnitude higher than the estimation from previous experiments that used macroscopic mat samples. The temperature dependence of the thermal conductivity of nanotubes exhibits a peak at 320 K due to the onset of umklapp phonon scattering. The measured thermoelectric power shows linear temperature dependence with a value of 80 microV/K at room temperature.
3,166 citations
"Dense Vertically Aligned Multiwalle..." refers methods in this paper
...Considering an estimated fill-in ratio of 10% of the MWCNTs, the effective thermal conductivity of the MWCNT array qualitatively matches with the previous measurement of an individual MWCNT [6]....
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...individual multiwalled carbon nanotube (MWCNT) showed 3000 W/m K at room temperature [6], while those using in-...
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TL;DR: A review of the literature on thermal transport in nanoscale devices can be found in this article, where the authors highlight the recent developments in experiment, theory and computation that have occurred in the past ten years and summarizes the present status of the field.
Abstract: Rapid progress in the synthesis and processing of materials with structure on nanometer length scales has created a demand for greater scientific understanding of thermal transport in nanoscale devices, individual nanostructures, and nanostructured materials. This review emphasizes developments in experiment, theory, and computation that have occurred in the past ten years and summarizes the present status of the field. Interfaces between materials become increasingly important on small length scales. The thermal conductance of many solid–solid interfaces have been studied experimentally but the range of observed interface properties is much smaller than predicted by simple theory. Classical molecular dynamics simulations are emerging as a powerful tool for calculations of thermal conductance and phonon scattering, and may provide for a lively interplay of experiment and theory in the near term. Fundamental issues remain concerning the correct definitions of temperature in nonequilibrium nanoscale systems. Modern Si microelectronics are now firmly in the nanoscale regime—experiments have demonstrated that the close proximity of interfaces and the extremely small volume of heat dissipation strongly modifies thermal transport, thereby aggravating problems of thermal management. Microelectronic devices are too large to yield to atomic-level simulation in the foreseeable future and, therefore, calculations of thermal transport must rely on solutions of the Boltzmann transport equation; microscopic phonon scattering rates needed for predictive models are, even for Si, poorly known. Low-dimensional nanostructures, such as carbon nanotubes, are predicted to have novel transport properties; the first quantitative experiments of the thermal conductivity of nanotubes have recently been achieved using microfabricated measurement systems. Nanoscale porosity decreases the permittivity of amorphous dielectrics but porosity also strongly decreases the thermal conductivity. The promise of improved thermoelectric materials and problems of thermal management of optoelectronic devices have stimulated extensive studies of semiconductor superlattices; agreement between experiment and theory is generally poor. Advances in measurement methods, e.g., the 3ω method, time-domain thermoreflectance, sources of coherent phonons, microfabricated test structures, and the scanning thermal microscope, are enabling new capabilities for nanoscale thermal metrology.
2,933 citations
"Dense Vertically Aligned Multiwalle..." refers background in this paper
...It is to be noted that the deposited Cr/Au with the optional indium thin layer has an overall thermal conductance 10 W/m K [21] such that their effects in the measurement can be neglected....
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TL;DR: In this paper, the authors have produced nanotube-in-oil suspensions and measured their effective thermal conductivity, which is anomalously greater than theoretical predictions and is nonlinear with nanotubes loadings.
Abstract: We have produced nanotube-in-oil suspensions and measured their effective thermal conductivity. The measured thermal conductivity is anomalously greater than theoretical predictions and is nonlinear with nanotube loadings. The anomalous phenomena show the fundamental limits of conventional heat conduction models for solid/liquid suspensions. We have suggested physical concepts for understanding the anomalous thermal behavior of nanotube suspensions. In comparison with other nanostructured materials dispersed in fluids, the nanotubes provide the highest thermal conductivity enhancement, opening the door to a wide range of nanotube applications.
2,546 citations
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