Picosecond optical studies of amorphous diamond and diamondlike carbon: Thermal conductivity and longitudinal sound velocity

Morath, Christopher J.; Maris, Humphrey J.; Cuomo, J. J.; Pappas, David; Grill, A.; Patel, V.; Doyle, J. P.; Saenger, K. L.

doi:10.1063/1.357560

Cited by 150 publications

(56 citation statements)

References 24 publications

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“…2a. Firstly, the simulations are in good qualitative agreement with the available experimental data [3][4][5][6][7][8][9][10], particularly given the magnitude of the experimental uncertainties. Secondly, the linear dependence on density is close to that measured experimentally by Shamsa et al, [4], with the gradients differing by just 20%.…”

supporting

confidence: 63%

“…Ref [3] Ref [4] Ref [5] Ref [6] Ref [7−8] Ref [8] Ref [9] Ref [10] diamonds in Fig. 2) exhibits no such variability, finding little deviation from a straight line fitted through the simulation data points.…”

mentioning

confidence: 99%

“…The triangles and circles in Fig. 2a illustrate the broad experimental spread, showing data from eight different authors using either the 3ω [3][4][5] or optical [6][7][8][9][10] methodology. Some of this variability is due to the specifics of sample preparation, prompting Shamsa et al [4] to perform a series of measurements on carbon films deposited in a systematic manner.…”

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confidence: 99%

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Effect of microstructure on the thermal conductivity of disordered carbon

Suarez-Martinez

Marks

2011

Applied Physics Letters

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Computational methods are used to control the degree of structural order in a variety of carbon materials containing primarily sp 2 bonding. Room-temperature thermal conductivities are computed using non-equilibrium molecular dynamics. Our results reproduce experimental data for amorphous and glassy carbons and confirm previously proposed structural models for vitreous carbons. An atomistic model is developed for highly oriented thin films seen experimentally, with a maximum computed thermal conductivity of 35 Wm −1 K −1 . This value is much higher than that of the amorphous and glassy structures, demonstrating that the microstructure influences the thermal conductivity more strongly than the density.

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confidence: 63%

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confidence: 99%

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confidence: 99%

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Effect of microstructure on the thermal conductivity of disordered carbon

Suarez-Martinez

Marks

2011

Applied Physics Letters

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“…The large variability of microstructures within this single class of materials provides a unique opportunity for exploring heat transport in disordered solids 2,3 and the applicability of the minimum thermal conductivity 4,5 to materials with heterogeneous microstructures that are common in thin films. 6,7 But we also anticipate that these new data will provide valuable insights on the high and low conductivities that can be produced in thin film a-C for applications in the thermal engineering of microdevices. 8,9 The concept of a ''minimum thermal conductivity'' ⌳ min is based on a theory of heat transport originally proposed by Einstein: 10 the atomic vibrations are assumed to be incoherent and therefore heat diffuses between the Einstein oscillators on a time scale of 1/2 the period of vibration.…”

Section: Introductionmentioning

confidence: 99%

“…7,[13][14][15] Data for bulk samples of high-dose neutron-irradiated diamond 13 and disordered carbon produced by high-pressure conversion of C 60 15 were measured by traditional steady-state methods; the conductivities of thin film samples were measured using the mirage effect 14 and picosecond thermoreflectance. 7 The thin film data were measured only for room temperature, and therefore the unusual temperature of the two bulk samples cannot be confirmed in the thin film samples. Furthermore, while picosecond reflectance is a powerful probe of elastic properties and interfacial transport of acoustic and thermal energy, measurements of thermal conductivity using this method are relatively indirect and require assumptions about the heat capacity of the films.…”

Section: Introductionmentioning

confidence: 99%

Thermal conductivity of amorphous carbon thin films

Bullen

O’Hara

Cahill

et al. 2000

Journal of Applied Physics

171

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Thermal conductivities ⌳ of amorphous carbon thin films are measured in the temperatures range 80-400 K using the 3 method. Sample films range from soft a-C:H prepared by remote-plasma deposition (⌳ϭ0.20 W m Ϫ1 K Ϫ1 at room temperature͒ to amorphous diamond with a large fraction of sp 3 bonded carbon deposited from a filtered-arc source (⌳ϭ2.2 W m Ϫ1 K Ϫ1 ). Effective-medium theory provides a phenomenological description of the variation of conductivity with mass density. The thermal conductivities are in good agreement with the minimum thermal conductivity calculated from the measured atomic density and longitudinal speed of sound.

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Thermal Management Material: Graphite

Kaburagi²,

2014

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Graphite has pronounced anisotropy in its properties. Thermal conductivity of graphite crystal is extremely high along its layer plane, as high as 2000 Wm À1 K À1 , much higher than metals, and very low across its layer plane, as low as 7 Wm À1 K À1 . This anisotropy gives high possibility for graphite as thermal management materials. Here, graphite membranes with high thermal conductivity along the surface for heat dissipation and with low conductivity perpendicular to the surface for heat insulation, in addition to graphite foams as container of phase change materials for heat energy storage, are reviewed, particularly referring to the preparations of various graphite materials. Thermal conductivity of diamond crystal is also high, 2500 Wm À1 K À1 , but it is very sensitive for structural defects, but that of graphitic materials is less sensitive for structural defects, suggesting that the latter is more practical for thermal management than the former.(along the layer plane) as %2000 Wm À1 K À1 , [1] much higher than metals, such as Cu and Ag, but very small k RT along the c-axis (perpendicular to the layer plane) as around 6-9 Wm À1 K À1[2] : graphite crystal can be highly conductive along the layer and be highly insulating perpendicular to the layer. This pronounced anisotropy is due to graphite structure, graphite layer consisting of strong s bonding, and parallel stacking of these layers by van der Waals bonding due to the interaction between p-electron clouds on neighboring layers. Diamond crystal, which consists of carbon atoms using sp 3 CÀ ÀC bonding, is isotropic and has the highest value of k RT in solids as %2200 Wm À1 K À1 . [3] Highly graphitized carbon materials exhibit very high thermal conductivities. A highly-oriented pyrolytic graphite (HOPG) is reported to have k RT of 1950 Wm À1 K À1 . [1,4] Recently, graphite films with high thermal conductivity have become commercially available for dissipating heat from electronic devices containing integrated circuits, such as personal computers and mobile phones. [5] The k RT of the commercially available graphite films is reported to be more than 1600 Wm À1 K À1 , more than four times higher than the values of Ag, which is known to have the highest k RT among metals. Carbon/carbon composites prepared from natural graphite flakes by using mesophase pitch as binder, followed by heat treatment at high temperatures, gives k RT of about 650 Wm À1 K À1 , higher than Ag. In order to develop practical materials having k high enough, the preparation of highly oriented and highly crystallized graphite is essential. Flexible graphite sheets prepared from natural graphite via [*] Prof. M. InagakiProfessor Emeritus

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Picosecond optical studies of amorphous diamond and diamondlike carbon: Thermal conductivity and longitudinal sound velocity

Cited by 150 publications

References 24 publications

Effect of microstructure on the thermal conductivity of disordered carbon

Effect of microstructure on the thermal conductivity of disordered carbon

Thermal conductivity of amorphous carbon thin films

Thermal Management Material: Graphite

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