Percolation of thermal conductivity in amorphous fluorocarbons

Ghossoub, Marc G.; Lee, Jung Hyun; Baris, Oksen T.; Cahill, David G.; Sinha, Sanjiv

doi:10.1103/physrevb.82.195441

Cited by 21 publications

(12 citation statements)

References 48 publications

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“…This is remarkably similar to a number of common polymers measured in the range of 0.1-0.25 W m -1 K -1 . 29,[87][88][89] The sheer mass and number of atoms comprising of the F21PA molecule, as it becomes large enough to accommodate internal scattering, may account for this similarity between the effective thermal conductivity of the molecule and larger polymer species. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 Figure 6.…”

Section: Acs Paragon Plus Environmentmentioning

confidence: 99%

Thermal Conductance across Phosphonic Acid Molecules and Interfaces: Ballistic versus Diffusive Vibrational Transport in Molecular Monolayers

Gaskins

Bulusu²,

Giordano³

et al. 2015

J. Phys. Chem. C

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The influence of planar organic linkers on thermal boundary conductance across hybrid interfaces has focused on the organic/inorganic interaction energy, rather than on vibrational mechanisms in the molecule. As a result, research into interfacial transport at planar organic monolayer junctions has treated molecular systems as thermally ballistic. We show that thermal conductance in phosphonic acid (PA) molecules is ballistic, and the thermal boundary conductance across metal/PA/sapphire interfaces is driven by the same phononic processes as those across metal/sapphire interfaces without PAs, with one exception. We find a more than 40% reduction in conductance across Henicosafluorododecyl phosphonic acid (F21PA) interfaces, independent of metal contact, despite similarities in structure, composition and terminal group to the variety of other PAs studied. Our results suggest diffusive scattering of thermal vibrations in F21PA, demonstrating a clear path toward modification of interfacial thermal transport based on knowledge of ballistic and diffusive scattering in single monolayer molecular interfacial films.

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Section: Acs Paragon Plus Environmentmentioning

confidence: 99%

Thermal Conductance across Phosphonic Acid Molecules and Interfaces: Ballistic versus Diffusive Vibrational Transport in Molecular Monolayers

Gaskins

Bulusu²,

Giordano³

et al. 2015

J. Phys. Chem. C

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“…Although basic rigidity theory predicts that the elastic modulus goes to zero below r c , this is not the case in experiment due to the presence of dihedral angle and VDW forces that contribute an underlying elasticity (He and Thorpe, 1985). In other hydrogenated/fluorinated materials, the Young's modulus/hardness tends toward zero at r c in the case of a-C:H/a-C:F (Ghossoub et al, 2010;King et al, 2013) or finite yet very low values below r c in the case of a-SiC:H/a-SiOC:H (Ross and Gleason, 2005;Trujillo et al, 2010;King et al, 2013), yet in a-BC:H, it remains relatively high. This "superatom" system is unique in that, in addition to VDW and related forces, we must also consider the intrinsic rigidity of the icosahedra as well as the fact that boron-based covalent bonds are extremely strong.…”

Section: Resultsmentioning

confidence: 96%

“…Rigidity threshold phenomena have also been investigated in other classes of materials wherein the incorporation of terminal hydrogen atoms or other groups is used to alter network connectivity, including a-Si:H (Kuschnereit et al, 1995), a-C:H (Boolchand et al, 1996), a-C:F (Ghossoub et al, 2010), a-SiC:H (King et al, 2013), a-SiCN:H (Gerstenberg and Taube, 1989), and a-SiOC:H (Ross and Gleason, 2005;Trujillo et al, 2010), with a few of these studies (Ross and Gleason, 2005;Trujillo et al, 2010;King et al, 2013) showing a convincing transition point, including via experimental modulus data. Finally, rigidity thresholds have been demonstrated in more complex materials such as proteins , zeolites (Sartbaeva et al, 2006), and cements (Bauchy et al, 2015), albeit only computationally.…”

Section: Introductionmentioning

confidence: 99%

Topological Constraint Theory Analysis of Rigidity Transition in Highly Coordinate Amorphous Hydrogenated Boron Carbide

et al. 2019

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Topological constraint theory (TCT) has revealed itself to be a powerful tool in interpreting the behaviors of amorphous solids. The theory predicts a transition between a "rigid" overconstrained network and a "floppy" underconstrained network as a function of connectivity or average coordination number, r . The predicted results have been shown experimentally for various glassy materials, the majority of these being based on 4-fold-coordinate networks such as chalcogenide and oxide glasses. Here, we demonstrate the broader applicability of topological constraint theory to uniquely coordinated amorphous hydrogenated boron carbide (a-BC:H), based on 6-fold-coordinate boron atoms arranged into partially hydrogenated interconnected 12-vertex icosahedra. We have produced a substantial set of plasma-enhanced chemical vapor deposited a-BC:H films with a large range of densities and network coordination, and demonstrate a clear threshold in Young's modulus as a function of r , ascribed to a rigidity transition. We investigate constraint counting strategies in this material and show that by treating icosahedra as "superatoms," a rigidity transition is observed within the range of the theoretically predicted r c value of 2.4 for covalent solids with bond-stretching and bond-bending forces. This experimental data set for a-BC:H is unique in that it represents a uniform change in connectivity with r and demonstrates a distinct rigidity transition with data points both above and below the transition threshold. Finally, we discuss how TCT can be applied to explain and optimize mechanical and dielectric properties in a-BC:H and related materials in the context of microelectronics applications.

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“…These exceptional properties arise from the highly cross‐linked molecular structure of this polymer coating. We also correlate these results with documented mechanical property data, and propose a design principle based on the concept of percolation of rigidity13, 14 to guide the synthesis of an all‐organic conformal coating that provides high modulus and hardness simultaneously with flexibility.…”

mentioning

confidence: 89%

“…This combination of flexibility and crack resistance with the high modulus, hardness and scratch resistance of these films is believed to arise in part from the underlying architecture of their covalent bonding structures. The concept of percolation of rigidity, first developed by Philips and further studied by many researchers,13, 14 is one measure of this property that was applied to both organic and inorganic materials. It defines a compositional transition from an underconstrained (non‐rigid) state to a constrained (rigid) one.…”

mentioning

confidence: 99%

One‐step electrodeposition of amorphous carbon films containing WO₃ with high conductivity and good wettability

Wan

Wang

Xue

2010

Surface & Interface Analysis

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Tungsten trioxide-incorporated hydrogenated amorphous carbon (WO 3 /a-C : H) films have been fabricated on a single-crystal silicon wafer by liquid phase electrodeposition using methanol as carbon source and tungsten carbonyl as incorporated reagent. The morphology, composition and structure of the films have been investigated by SEM, XPS, Raman scattering spectroscopy, Fourier transform infrared spectroscopy (FTIR) and Transmission electron microscope (TEM), respectively. The effects of WO 3 incorporation on the electrical and wetting properties were studied in detail. The characterization results showed that tungsten trioxide nanocrystalline particles with diameters in the range of 10-20 nm were homogenously embedded in the amorphous carbon films. Also, the electrical conductivity and wetting ability of the films were strongly improved due to the contribution of the tungsten trioxide.

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Percolation of thermal conductivity in amorphous fluorocarbons

Cited by 21 publications

References 48 publications

Thermal Conductance across Phosphonic Acid Molecules and Interfaces: Ballistic versus Diffusive Vibrational Transport in Molecular Monolayers

Thermal Conductance across Phosphonic Acid Molecules and Interfaces: Ballistic versus Diffusive Vibrational Transport in Molecular Monolayers

Topological Constraint Theory Analysis of Rigidity Transition in Highly Coordinate Amorphous Hydrogenated Boron Carbide

One‐step electrodeposition of amorphous carbon films containing WO₃ with high conductivity and good wettability

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Percolation of thermal conductivity in amorphous fluorocarbons

Cited by 21 publications

References 48 publications

Thermal Conductance across Phosphonic Acid Molecules and Interfaces: Ballistic versus Diffusive Vibrational Transport in Molecular Monolayers

Thermal Conductance across Phosphonic Acid Molecules and Interfaces: Ballistic versus Diffusive Vibrational Transport in Molecular Monolayers

Topological Constraint Theory Analysis of Rigidity Transition in Highly Coordinate Amorphous Hydrogenated Boron Carbide

One‐step electrodeposition of amorphous carbon films containing WO3 with high conductivity and good wettability

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One‐step electrodeposition of amorphous carbon films containing WO₃ with high conductivity and good wettability