Phonon thermal conductivity of monolayer MoS2: A comparison with single layer graphene

2014 ◽  
Vol 105 (10) ◽  
pp. 103902 ◽  
Author(s):  
Xiaolin Wei ◽  
Yongchun Wang ◽  
Yulu Shen ◽  
Guofeng Xie ◽  
Huaping Xiao ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Single Layer ◽  
Single Layer Graphene ◽  
Monolayer Mos2 ◽  
Phonon Thermal Conductivity ◽  
Layer Graphene

Thermal Conductivity Reduction in Few-Layer Graphene

2011 ◽  
Author(s):  
Dhruv Singh ◽  
Jayathi Y. Murthy ◽  
Timothy S. Fisher
Keyword(s):  
Thermal Conductivity ◽  
Weak Coupling ◽  
Phonon Scattering ◽  
Single Layer ◽  
Acoustic Mode ◽  
Single Layer Graphene ◽  
Boltzmann Transport ◽  
Layer Graphene ◽  
Out Of Plane ◽  
Few Layer Graphene

Using the linearized Boltzmann transport equation and perturbation theory, we analyze the reduction in the intrinsic thermal conductivity of few-layer graphene sheets accounting for all possible three-phonon scattering events. Even with weak coupling between layers, a significant reduction in the thermal conductivity of the out-of-plane acoustic modes is apparent. The main effect of this weak coupling is to open many new three-phonon scattering channels that are otherwise absent in graphene. The highly restrictive selection rule that leads to a high thermal conductivity of ZA phonons in single-layer graphene is only weakly broken with the addition of multiple layers, and ZA phonons still dominate thermal conductivity. We also find that the decrease in thermal conductivity is mainly caused by decreased contributions of the higher-order overtones of the fundamental out-of-plane acoustic mode. Moreover, the extent of reduction is largest when going from single to bilayer graphene and saturates for four layers. The results compare remarkably well over the entire temperature range with measurements of of graphene and graphite.

Mode dependent lattice thermal conductivity of single layer graphene

2014 ◽  
Vol 116 (15) ◽  
pp. 153503 ◽  
Author(s):  
Zhiyong Wei ◽  
Juekuan Yang ◽  
Kedong Bi ◽  
Yunfei Chen
Keyword(s):  
Thermal Conductivity ◽  
Lattice Thermal Conductivity ◽  
Single Layer ◽  
Single Layer Graphene ◽  
Layer Graphene

Substrate Effects on the Thermal Conductivity of Single Layer Supported Graphene

2011 ◽  
Author(s):  
Z. Wei ◽  
C. Dames ◽  
Y. Chen
Keyword(s):  
Thermal Conductivity ◽  
Silicon Dioxide ◽  
Single Layer ◽  
Single Layer Graphene ◽  
Dynamics Model ◽  
Graphene Flake ◽  
Substrate Effects ◽  
Layer Graphene ◽  
Lennard Jones ◽  
Non Equilibrium Molecular Dynamics

A non-equilibrium molecular dynamics model is developed to calculate the thermal conductivity of single layer graphene supported on silicon dioxide. We use the Tersoff potential to describe the carbon-carbon interactions within graphene, and a Lennard-Jones (LJ) potential to describe the interactions between graphene and silicon dioxide. To overcome possible artifacts of thermal expansion, the model avoids using any periodic or fixed boundary conditions for the graphene flake. For both smooth and rough substrates, the simulations show that increasing the LJ coupling strength between graphene and substrate can reduce the in-plane thermal conductivity of graphene. We also investigated the effects of roughness. The simulations show that the thermal conductivity is sensitive to the roughness only when the coupling is large. These results indicate how the thermal properties of graphene may be modified by adjusting the coupling and roughness of the substrate.

The Phonon Thermal Conductivity of a Single-Layer Graphene From Complete Phonon Dispersion Relations

2010 ◽  
Author(s):  
Yunfeng Gu ◽  
Zhonghua Ni ◽  
Minhua Chen ◽  
Kedong Bi ◽  
Yunfei Chen
Keyword(s):  
Thermal Conductivity ◽  
Acoustic Phonon ◽  
Phonon Scattering ◽  
Phonon Dispersion ◽  
Single Layer ◽  
Single Layer Graphene ◽  
Optical Phonons ◽  
Relaxation Rates ◽  
Phonon Thermal Conductivity ◽  
Transverse Acoustic

In this paper, the phonon scattering mechanisms of a single layer graphene are investigated based on the complete phonon dispersion relations. According to the selection rules that a phonon scattering process should obey the energy and momentum conservation conditions, the relaxation rates of combing and splitting Umklapp processes can be calculated by integrating the intersection lines between different phonon mode surfaces in the phonon dispersion relation space. The dependence of the relaxation rates on the wave vector directions is presented with a three dimensional surfaces over the first Brillion zone. It is found that the reason for the optical phonons contributing a little to heat transfer is attributed to the strong Umklapp processes but not to their low group velocities. The combing Umklapp scattering processes involved by the optical phonons mainly decrease the acoustic phonon thermal conductivity, while the splitting Umklapp scattering processes of the optical phonons mainly restrict heat conduction by the optical phonons themselves. Neglecting the splitting processes, the optical phonons can contribute more energy than that carried by the acoustic phonons. Based on the calculated phonon relaxation time, the thermal conductivities contributed from different mode phonons can be evaluated. At low temperatures, both longitudinal and in-plane transverse acoustic phonon thermal conductivities have T2 temperature dependence, and the out-of-plane transverse acoustic phonon thermal conductivity is proportion to T3/2. At room temperature, the calculated thermal conductivity is on the order of a few thousands W/m.K depending on the sample size and the edge roughness, which is in agreement with the recently measured data.

The Phonon Thermal Conductivity of Single-Layer Graphene From Complete Phonon Dispersion Relations

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
Yunfeng Gu ◽  
Zhonghua Ni ◽  
Minhua Chen ◽  
Kedong Bi ◽  
Yunfei Chen
Keyword(s):  
Thermal Conductivity ◽  
Acoustic Phonon ◽  
Phonon Scattering ◽  
Phonon Dispersion ◽  
Single Layer ◽  
Single Layer Graphene ◽  
Optical Phonons ◽  
Relaxation Rates ◽  
Phonon Thermal Conductivity ◽  
Transverse Acoustic

In this paper, the phonon scattering mechanisms of single-layer graphene are investigated based on the complete phonon dispersion relations. According to the selection rules that a phonon scattering process should obey the energy and momentum conservation conditions, the relaxation rates of combining and splitting umklapp processes can be calculated by integrating the intersection lines between different phonon mode surfaces in the phonon dispersion relation space. The dependence of the relaxation rates on the wave vector directions is presented with a three-dimensional surface over the first Brillouin zone. It is found that the reason for the optical phonons contributing little to heat transfer is attributed to the strong umklapp processes but not to their low phonon group velocities. The combining umklapp scattering processes involving the optical phonons mainly decrease the acoustic phonon thermal conductivity, while the splitting umklapp scattering processes of the optical phonons mainly restrict heat conduction by the optical phonons themselves. Neglecting the splitting processes, the optical phonons can contribute more energy than that carried by the acoustic phonons. Based on the calculated phonon relaxation time, the thermal conductivities contributed from different mode phonons can be evaluated. At low temperatures, both longitudinal and in-plane transverse acoustic phonon thermal conductivities have T2 temperature dependence, and the out-of-plane transverse acoustic phonon thermal conductivity is proportion to T3/2. The calculated thermal conductivity is on the order of a few thousands W/(m K) at room temperature, depending on the sample size and the edge roughness, and is in agreement well with the recently measured data in the temperature range from about 350 K to 500 K.

Tuning Thermal Conductivity With Mechanical Strain

2010 ◽  
Author(s):  
Xiaobo Li ◽  
Jun Liu ◽  
Ronggui Yang
Keyword(s):  
Thermal Conductivity ◽  
Silicon Nanowires ◽  
Phonon Dispersion ◽  
Compressive Strain ◽  
Mechanical Strain ◽  
Single Layer ◽  
Polymer Materials ◽  
Single Layer Graphene ◽  
Layer Graphene ◽  
Carbon Based

Mechanical strain provides an efficient way for tuning thermal conductivity of materials. In this study, molecular dynamics (MD) simulation is performed to systematically study the strain effects on the lattice thermal conductivity of silicon and carbon based materials (mainly nanostructures: Si nanowire and thin film, single-walled carbon naotube (SWCNT) and single layer graphene) and bulk polymer materials. Results show that thermal conductivity of the strained silicon nanowires and thin films decreases continuously when the strain changes from compressive to tensile. However, the thermal conductivity has a peak value under compressive strain for SWCNT and at zero strain for single layer graphene. In contrast, thermal conductivity of polymer materials increases with increasing tensile strain. The underlying mechanisms are analyzed in this paper for both types of materials. We found that the thermal conductivity of silicon and carbon based materials can be related to the phonon dispersion curve shift and structural buckling under strain and for polymer chains thermal conductivity directly connects to the orientations of the chains. This thermal conductivity dependence with strain can guide us to tune the thermal conductivity for materials in applications.

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