The Effects of Van Der Waals Bonding Strength on the In-Plane Lattice Thermal Conductivities of Multilayer Thin Films

2012 ◽  
Author(s):  
Weiyu Chen ◽  
Zhonghua Ni ◽  
Juekuan Yang ◽  
Yan Zhang ◽  
Deyu Li ◽  
...  
Keyword(s):  
Thin Films ◽  
Thermal Conductivity ◽  
Bonding Strength ◽  
Van Der Waals ◽  
Interface Roughness ◽  
Multilayer Thin Films ◽  
Continuous Increase ◽  
Non Equilibrium Molecular Dynamics ◽  
The Impact ◽  
Thermal Conductivities

A non-equilibrium molecular dynamics (NEMD) simulation model is established to investigate the impact of vdW strength on thermal transport along the in-plane direction in argon bi-layer films (BLFs) and silicon BLFs. Simulation results indicate that higher strength leads to a higher in-plane thermal conductivity. However, interface roughness also increases with the continuous increase of the van der Waals (vdW) strength and leads to the reduction of thermal conductivities. The bonding strength does play an important role in manipulating thermal conductivity of multilayer thin films.

scholarly journals Exceptional in-plane and interfacial thermal transport in graphene/2D-SiC van der Waals heterostructures

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Md. Sherajul Islam ◽  
Imon Mia ◽  
Shihab Ahammed ◽  
Catherine Stampfl ◽  
Jeongwon Park
Keyword(s):  
Thermal Conductivity ◽  
Heat Conduction ◽  
Van Der Waals ◽  
New Physics ◽  
Infinite Length ◽  
Interatomic Potentials ◽  
Van Der Waals Heterostructures ◽  
Functional Efficiency ◽  
Out Of Plane ◽  
The Impact

AbstractGraphene based van der Waals heterostructures (vdWHs) have gained substantial interest recently due to their unique electrical and optical characteristics as well as unprecedented opportunities to explore new physics and revolutionary design of nanodevices. However, the heat conduction performance of these vdWHs holds a crucial role in deciding their functional efficiency. In-plane and out-of-plane thermal conduction phenomena in graphene/2D-SiC vdWHs were studied using reverse non-equilibrium molecular dynamics simulations and the transient pump-probe technique, respectively. At room temperature, we determined an in-plane thermal conductivity of ~ 1452 W/m-K for an infinite length graphene/2D-SiC vdWH, which is superior to any graphene based vdWHs reported yet. The out-of-plane thermal resistance of graphene → 2D-SiC and 2D-SiC → graphene was estimated to be 2.71 × 10−7 km2/W and 2.65 × 10−7 km2/W, respectively, implying the absence of the thermal rectification effect in the heterobilayer. The phonon-mediated both in-plane and out-of-plane heat transfer is clarified for this prospective heterobilayer. This study furthermore explored the impact of various interatomic potentials on the thermal conductivity of the heterobilayer. These findings are useful in explaining the heat conduction at the interfaces in graphene/2D-SiC vdWH and may provide a guideline for efficient design and regulation of their thermal characteristics.

Chain conformation-dependent thermal conductivity of amorphous polymer blends: the impact of inter- and intra-chain interactions

2016 ◽  
Vol 18 (47) ◽  
pp. 32146-32154 ◽  
Author(s):  
Xingfei Wei ◽  
Teng Zhang ◽  
Tengfei Luo
Keyword(s):  
Thermal Conductivity ◽  
Polymer Blends ◽  
Amorphous Polymer ◽  
Scientific Research ◽  
Industrial Applications ◽  
Chain Conformation ◽  
The Impact ◽  
Thermal Conductivities

Polymers with high thermal conductivities are of great interest for both scientific research and industrial applications.

Phonon scattering due to van der Waals forces in the lattice thermal conductivity of Bi2Te3 thin films

2015 ◽  
Vol 117 (1) ◽  
pp. 015103 ◽  
Author(s):  
Kyeong Hyun Park ◽  
Mohamed Mohamed ◽  
Zlatan Aksamija ◽  
Umberto Ravaioli
Keyword(s):  
Thin Films ◽  
Thermal Conductivity ◽  
Lattice Thermal Conductivity ◽  
Phonon Scattering ◽  
Van Der Waals ◽  
Van Der Waals Forces

Correlation of Electrical and Physical Properties of SIMOX BOX Affected by Various Implantation Parameters

1996 ◽  
Vol 446 ◽  
Author(s):  
J. U. Yoon ◽  
G. N. Kim ◽  
J‐H Y. Krska ◽  
J. E. Chung ◽  
L. P. Allen ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Substrate Temperature ◽  
High Field ◽  
Beam Current ◽  
Interface Roughness ◽  
Surface Photovoltage ◽  
Buried Oxide ◽  
Current Variation ◽  
The Impact ◽  
Substrate Temperatures

AbstractThe impact of two implant parameters, namely the implant substrate temperature and implant beam current, on the physical and electrical properties of SIMOX buried oxide are investigated. Three implant substrate temperatures, 540 °C, 590 °C, and 640 °C and three beam current, 45 mA, 55 mA, 65 mA, are investigated. Results from thermal conductivity and surface photovoltage measurements show no apparent differences between samples. Results from interface roughness shows a decreasing trend as the substrate temperature and beam current increases. For the samples with different implant temperatures, the high‐field conduction shows an opposite dependence for top‐interface versus substrate injection. This behavior can be explained by the conservation of silicon in the buried oxide. Correlation of surface photovoltage and high‐field conduction shows weak positive dependency while that of interface roughness and high‐field conduction shows dependency only when the sets of temperature variation and beam current variation are decoupled.

Anderson Localization of Phonons in Random Multilayer Thin Films

2012 ◽  
Vol 1404 ◽  
Author(s):  
Anthony Frachioni ◽  
Bruce White
Keyword(s):  
Thin Films ◽  
Thermal Conductivity ◽  
Thermoelectric Materials ◽  
Anderson Localization ◽  
Lattice Thermal Conductivity ◽  
Waste Heat ◽  
Mean Free Path ◽  
The United States ◽  
Energy Scavenging ◽  
Multilayer Thin Films

ABSTRACT1020 Joules of energy are generated by the United States each year; 60% of this energy is lost to waste heat [1]. Thermoelectric based energy scavenging has tremendous potential for the recovery of significant quantities of this waste heat. However, utilization of thermoelectric devices is limited due to relatively low energy conversion efficiency and the utilization of relatively scarce materials. This work focuses on generating sustainable and efficient thermoelectric materials through modifications to the lattice vibrations of materials with excellent thermoelectric electronic properties (Seebeck coefficients larger than 500 μV/K). In particular, Anderson localization of phonons in random multilayer thin films has been explored as a means for reducing lattice thermal conductivity to values approaching that of aerogels (∼10 mW/m-K). Silicon has been a sample of choice due to its high crust abundance and Seebeck coefficient. Reverse non-equilibrium molecular dynamics simulations have been utilized to determine the thermal conductivity of structures of interest. Simulations with pure Lennard-Jones argon solids have been performed to establish a methodology and to characterize the effect of different kinds of disorder prior to the examination of silicon. The simulation results indicate that mass disorder confined to randomly selected planes to be an effective way in which to reduce lattice thermal conductivity with the lattice thermal conductivity decreasing by a factor of thirty (to 4 mW/m-K) in the argon case and a factor of over ten thousand (to 15 mW/m-K) for silicon. Based on models in which the charge carrier mean free path is limited by scattering from the planes with mass disorder, the mobility of silicon is expected to reach values of 10 cm2/V-s. At this mobility the thermoelectric figure of merit, ZT, (utilizing the Wiedeman-Franz law to calculate the electronic thermal conductivity) varies between 4.5 and 11 as the mass ratio of the disordered planes is varied from 4 to 10 in 20% of the lattice planes. These results indicate that the pursuit of nanostructured thermoelectric materials in the form of random multilayers may provide a path to efficient and sustainable thermoelectric materials.

scholarly journals Molecular Dynamics Simulations on Influence of Defect on Thermal Conductivity of Silicon Nanowires

2021 ◽  
Vol 9 ◽  
Author(s):  
Hao Li ◽  
Qiancheng Rui ◽  
Xiwen Wang ◽  
Wei Yu
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Silicon Nanowires ◽  
Surface Defects ◽  
Low Frequency ◽  
Simulation Method ◽  
Dynamics Simulation ◽  
Non Equilibrium Molecular Dynamics ◽  
Dynamics Simulations ◽  
The Impact

A non-equilibrium molecular dynamics simulation method is conducted to study the thermal conductivity (TC) of silicon nanowires (SiNWs) with different types of defects. The impacts of defect position, porosity, temperature, and length on the TC of SiNWs are analyzed. The numerical results indicate that SiNWs with surface defects have higher TC than SiNWs with inner defects, the TC of SiNWs gradually decreases with the increase of porosity and temperature, and the impact of temperature on the TC of SiNWs with defects is weaker than the impact on the TC of SiNWs with no defects. The TC of SiNWs increases as their length increases. SiNWs with no defects have the highest corresponding frequency of low-frequency peaks of phonon density of states; however, when SiNWs have inner defects, the lowest frequency is observed. Under the same porosity, the average phonon participation of SiNWs with surface defects is higher than that of SiNWs with inner defects.

Performance Analysis of Micro-Raman Spectroscopy Models for Thermal Conductivity Calculation

2021 ◽  
Author(s):  
Taher Meydando ◽  
Nazli Donmezer
Keyword(s):  
Thin Films ◽  
Thermal Conductivity ◽  
Raman Spectroscopy ◽  
Phonon Scattering ◽  
Raman Laser ◽  
Current Approach ◽  
Slab Model ◽  
Boltzmann Transport ◽  
Micro Raman Spectroscopy ◽  
Thermal Conductivities

Abstract Micro-Raman spectroscopy has been preferred recently to measure the thermal conductivity of thin-films due to its nondestructive and non-contact nature. However, the thermal size effects originating from both localized heat generation from Raman laser and phonon scattering at boundaries may cause erroneous estimation of the thermal conductivities with the current approach. In this study, the gray phonon Boltzmann transport equation (BTE) is solved to improve the results of micro-Raman thermal conductivity measurements. Due to the frequency independence of single phonon mode in the gray BTE model, our method stays ahead of most theoretical methods in calculation time while giving adequate agreement with the literature data. The improved thermal conductivities are evaluated at various laser powers and focal lengths. Subsequently, the values of thermal conductivities are compared with a simple slab model in which the deduction of thermal conductivity in sub-micron thicknesses is calculated using reduced heat flux through the slab resulting from phonon directional energy densities. The results show that subsequent errors are present in measuring the thermal conductivity of relatively thick, thin films with this technique which are noticed by comparing with the simple slab model. Finally, a virtual micro-Raman thermography experiment is developed, and its validity is verified by the same slab model.

Thermal Conductivity of Nano-Porous Bismuth Antimony Telluride

2010 ◽  
Author(s):  
Saburo Tanaka ◽  
Masayuki Takashiri ◽  
Koji Miyazaki
Keyword(s):  
Thin Films ◽  
Thermal Conductivity ◽  
Phonon Scattering ◽  
Antimony Telluride ◽  
Bismuth Antimony Telluride ◽  
Porous Thin Films ◽  
Average Grain Size ◽  
Bismuth Antimony ◽  
Bulk Alloys ◽  
Thermal Conductivities

Bismuth antimony telluride (Bi0.4Te3.0Sb1.6) nano-porous thin films have been prepared and measured their thermal conductivities. The thin films exhibit an average grain size of 50 nm and random crystal orientation. The cross-plane thermal conductivity is measured by a differential 3ω method at temperature range from 100 to 300 K, and the determined thermal conductivities are from 0.09 to 0.18 W/(m·K). As compared with bulk alloys at the same atomic composition, the nano-porous thin films exhibit an eightfold reduction in the thermal conductivity. For more detail analysis, the reduction of the thermal conductivity is examined by a simplified phonon gas model on a single crystal of bulk Bi2Te3. The analytical model fairly agreed with the experimental results, and thus we consider that the thermal conductivity is reduced by the strong phonon scattering at the nano-pores.

scholarly journals Lattice thermal transport in two-dimensional alloys and fractal heterostructures

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Aravind Krishnamoorthy ◽  
Nitish Baradwaj ◽  
Aiichiro Nakano ◽  
Rajiv K. Kalia ◽  
Priya Vashishta
Keyword(s):  
Thermal Conductivity ◽  
Thermal Transport ◽  
Lattice Thermal Conductivity ◽  
Material Design ◽  
Two Dimensional ◽  
Scale Free ◽  
Dopant Atoms ◽  
Non Equilibrium Molecular Dynamics ◽  
Dynamics Simulations ◽  
The Impact

AbstractEngineering thermal transport in two dimensional materials, alloys and heterostructures is critical for the design of next-generation flexible optoelectronic and energy harvesting devices. Direct experimental characterization of lattice thermal conductivity in these ultra-thin systems is challenging and the impact of dopant atoms and hetero-phase interfaces, introduced unintentionally during synthesis or as part of deliberate material design, on thermal transport properties is not understood. Here, we use non-equilibrium molecular dynamics simulations to calculate lattice thermal conductivity of $${\mathrm {(Mo|W)Se_2}}$$ ( Mo | W ) Se 2 monolayer crystals including $${\mathrm {Mo}}_{1-x}{\mathrm {W}}_x{\mathrm {Se_2}}$$ Mo 1 - x W x Se 2 alloys with substitutional point defects, periodic $${\mathrm {MoSe_2}|\mathrm {WSe_2}}$$ MoSe 2 | WSe 2 heterostructures with characteristic length scales and scale-free fractal $${\mathrm {MoSe_2}}|{\mathrm {WSe_2}}$$ MoSe 2 | WSe 2 heterostructures. Each of these features has a distinct effect on phonon propagation in the crystal, which can be used to design fractal and periodic alloy structures with highly tunable thermal conductivities. This control over lattice thermal conductivity will enable applications ranging from thermal barriers to thermoelectrics.

The Thermal Conductivity of Organic Vapours: The Influence of Molecular Interaction

1953 ◽  
Vol 6 (1) ◽  
pp. 1 ◽  
Author(s):  
RG Vines
Keyword(s):  
Thermal Conductivity ◽  
Molecular Interaction ◽  
Van Der Waals ◽  
Van Der Waals Forces ◽  
Dipole Interaction ◽  
Conductivity Variation ◽  
Other Substances ◽  
Thermal Conductivities

A study has been made of the thermal conductivities of a number of simple organic vapours at various pressures and temperatures. The measurements indicate that the variation of conductivity with pressure is a function of gas imperfection ; for substances with appreciable dipole interaction the effect is large, but for other substances where gas imperfection involves only van der Waals forces, the effect is much less. In all cases it is probable that the change in specific beat of the vapour with pressure is the main cause of the observed conductivity variation.

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