The role of three-phonon Normal processes in the thermal conductivity of graphene

2012 ◽  
Vol 1404 ◽  
Author(s):  
Ayman Alofi ◽  
Gyaneshwar P. Srivastava
Keyword(s):  
Thermal Conductivity ◽  
Relaxation Time ◽  
Room Temperature ◽  
Phonon Dispersion ◽  
Correction Term ◽  
Single Mode ◽  
Analytical Expressions ◽  
Phonon Dispersion Relations ◽  
Time Theory

ABSTRACTWe have studied the thermal conductivity of graphene using Callaway’s effective relax-ation time theory and by employing analytical expressions for phonon dispersion relations and vibrational density of states based on the semicontinuum model by Nihira and Iwata. It is found that consideration of the momentum conserving nature of three-phonon Normal pro-cesses is very important for explaining the magnitude as well as the temperature dependence of the experimentally measured results. At room temperature, the N-drift contribution (the correction term in Callaway’s theory) provides 94% addition to the result obtained from the single-mode relaxation time theory, clearly suggesting that the single-mode relaxation time approach is inadequate for describing the phonon conductivity of graphene.

Effect of Tensile Strain on Thermal Properties of Graphene

2014 ◽  
Vol 1661 ◽  
Author(s):  
Ayman Salman Alofi ◽  
Gyaneshwar P. Srivastava
Keyword(s):  
Thermal Conductivity ◽  
Relaxation Time ◽  
Thermal Properties ◽  
Specific Heat ◽  
Density Of States ◽  
Tensile Strain ◽  
Phonon Dispersion ◽  
Analytical Expressions ◽  
Vibrational Density ◽  
Phonon Dispersion Relations

ABSTRACTWe have employed a semicontinuum model to investigate the effect of tensile strain on thermal properties of graphene. Analytical expressions derived by Nihira and Iwata for phonon dispersion relations and vibrational density of states are employed, based on the semicontinuum model proposed by Komatsu and Nagamiya. The thermal conductivity is computed within the framework of Callaway’s effective relaxation time theory. It is found that thermal properties of graphene are quite sensitive to tensile strain. In the presence of tensile strain, the specific heat increases but the thermal conductivity decreases.

Role of Phonon Dispersion in Lattice Thermal Conductivity Modeling

2004 ◽  
Vol 126 (3) ◽  
pp. 376-380 ◽  
Author(s):  
J. D. Chung ◽  
A. J. H. McGaughey ◽  
M. Kaviany
Keyword(s):  
Thermal Conductivity ◽  
Relaxation Time ◽  
Lattice Thermal Conductivity ◽  
Phonon Dispersion ◽  
Phonon Relaxation Time ◽  
Dynamics Simulations ◽  
Transfer Mechanisms ◽  
Conductivity Modeling ◽  
Fitting Parameters

The role of phonon dispersion in the prediction of the thermal conductivity of germanium between temperatures of 2 K and 1000 K is investigated using the Holland approach. If no dispersion is assumed, a large, nonphysical discontinuity is found in the transverse phonon relaxation time over the entire temperature range. However, this effect is masked in the final prediction of the thermal conductivity by the use of fitting parameters. As the treatment of the dispersion is refined, the magnitude of the discontinuity is reduced. At the same time, discrepancies between the high temperature predictions and experimental data become apparent, indicating that the assumed heat transfer mechanisms (i.e., the relaxation time models) are not sufficient to account for the expected thermal transport. Molecular dynamics simulations may be the most suitable tool available for addressing this issue.

Lattice Thermal Conductivity Modelling of a Diatomic Nanoscale Material

2020 ◽  
Vol 10 (5) ◽  
pp. 602-609
Author(s):  
Adil H. Awad
Keyword(s):  
Thermal Conductivity ◽  
Lattice Thermal Conductivity ◽  
Phonon Scattering ◽  
Correction Term ◽  
Nanoscale Material ◽  
New Approach ◽  
Two Samples ◽  
Conductivity Modelling ◽  
Callaway Model

Introduction: A new approach for expressing the lattice thermal conductivity of diatomic nanoscale materials is developed. Methods: The lattice thermal conductivity of two samples of GaAs nanobeam at 4-100K is calculated on the basis of monatomic dispersion relation. Phonons are scattered by nanobeam boundaries, point defects and other phonons via normal and Umklapp processes. Methods: A comparative study of the results of the present analysis and those obtained using Callaway formula is performed. We clearly demonstrate the importance of the utilised scattering mechanisms in lattice thermal conductivity by addressing the separate role of the phonon scattering relaxation rate. The formulas derived from the correction term are also presented, and their difference from Callaway model is evident. Furthermore their percentage contribution is sufficiently small to be neglected in calculating lattice thermal conductivity. Conclusion: Our model is successfully used to correlate the predicted lattice thermal conductivity with that of the experimental observation.

scholarly journals Phonon hydrodynamics and ultrahigh–room-temperature thermal conductivity in thin graphite

Science ◽  
2020 ◽  
Vol 367 (6475) ◽  
pp. 309-312 ◽  
Author(s):  
Yo Machida ◽  
Nayuta Matsumoto ◽  
Takayuki Isono ◽  
Kamran Behnia
Keyword(s):  
Thermal Conductivity ◽  
Thermal Diffusivity ◽  
Wide Temperature Range ◽  
Room Temperature ◽  
Phonon Dispersion ◽  
High Conductivity ◽  
Temperature Range ◽  
A Value ◽  
Out Of Plane ◽  
Intimate Link

Allotropes of carbon, such as diamond and graphene, are among the best conductors of heat. We monitored the evolution of thermal conductivity in thin graphite as a function of temperature and thickness and found an intimate link between high conductivity, thickness, and phonon hydrodynamics. The room-temperature in-plane thermal conductivity of 8.5-micrometer-thick graphite was 4300 watts per meter-kelvin—a value well above that for diamond and slightly larger than in isotopically purified graphene. Warming enhances thermal diffusivity across a wide temperature range, supporting partially hydrodynamic phonon flow. The enhancement of thermal conductivity that we observed with decreasing thickness points to a correlation between the out-of-plane momentum of phonons and the fraction of momentum-relaxing collisions. We argue that this is due to the extreme phonon dispersion anisotropy in graphite.

Impact of surface bond-order loss on phonon dispersion relations and thermal conductivity of cylindrical Si nanowires

2006 ◽  
Vol 74 (15) ◽  
Author(s):  
T. C. Au Yeung ◽  
M. X. Gu ◽  
Chang Q. Sun ◽  
George C. K. Chen ◽  
D. W. K. Wong ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Bond Order ◽  
Phonon Dispersion ◽  
Dispersion Relations ◽  
Si Nanowires ◽  
Surface Bond ◽  
Phonon Dispersion Relations

Built-in-polarization field effect on intrinsic and extrinsic thermal conductivities of AlN/GaN/AlN quantum well

2015 ◽  
Vol 29 (21) ◽  
pp. 1550149 ◽  
Author(s):  
A. Pansari ◽  
V. Gedam ◽  
B. K. Sahoo
Keyword(s):  
Thermal Conductivity ◽  
Relaxation Time ◽  
Quantum Well ◽  
Room Temperature ◽  
Mean Free Path ◽  
Polarization Field ◽  
Polarization Mechanism ◽  
Negative Effect ◽  
Phonon Velocity ◽  
Thermal Conductivities

In this paper, the effect of built-in-polarization field on lattice thermal conductivity of AlN/GaN/AlN quantum well (QW) has been theoretically investigated. The built-in-polarization field at the hetero-interface of GaN/AlN modifies elastic constant, phonon velocity and Debye temperature of GaN QW. The relaxation time of acoustic phonons (AP) in various scattering processes in GaN with and without built-in-polarization field has been computed at room temperature. The result shows that combined relaxation time of AP is enhanced by built-in-polarization field and implies a longer mean free path. The revised intrinsic and extrinsic thermal conductivities of GaN have been estimated. The theoretical analysis shows that up to a certain temperature the polarization field acts as negative effect and reduces the thermal conductivities. However, after this temperature both thermal conductivities are significantly contributed by polarization field. This gives the idea of temperature dependence of polarization effect which signifies the pyro-electric character of GaN. The intrinsic thermal conductivity at room temperature for with and without polarization mechanism is found to be 491 Wm -1 K -1 and 409 Wm -1 K -1, respectively i.e., 20% enhancement. However, the extrinsic thermal conductivity at room temperature for with and without polarization mechanism is found to be 280 Wm -1 K -1 and 245 Wm -1 K -1, respectively i.e., 13% enhancement. The method we have developed may be taken into account during the simulation of heat transport in optoelectronic nitride devices to minimize the self-heating processes and in polarization engineering strategies to optimize the thermoelectric performance of GaN alloys.

scholarly journals Low thermal conductivity in a modular inorganic material with bonding anisotropy and mismatch

Science ◽  
2021 ◽  
pp. eabh1619
Author(s):  
Quinn D. Gibson ◽  
Tianqi Zhao ◽  
Luke M. Daniels ◽  
Helen C. Walker ◽  
Ramzy Daou ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Room Temperature ◽  
Inorganic Material ◽  
Phonon Dispersion ◽  
Spatial Arrangement ◽  
Vibrational Modes ◽  
Crystalline Materials ◽  
Low Thermal Conductivity ◽  
Transverse Modes ◽  
Different Types

The thermal conductivity of crystalline materials cannot be arbitrarily low as the intrinsic limit depends on the phonon dispersion. We used complementary strategies to suppress the contribution of the longitudinal and transverse phonons to heat transport in layered materials containing different types of intrinsic chemical interface. BiOCl and Bi2O2Se encapsulate these design principles for longitudinal and transverse modes respectively, and the bulk superlattice material Bi4O4SeCl2 combines these effects by ordering both interface types within its unit cell to reach an extremely low thermal conductivity of 0.1 W K−1 m−1 at room temperature along its stacking direction. This value comes within a factor of four of air. We demonstrated that chemical control of the spatial arrangement of distinct interfaces can synergically modify vibrational modes to minimize thermal conductivity.

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