Thermal Transport in Few-Quintuple Bi2Te3 Thin Films and Nanoribbons

2011 ◽  
Author(s):  
Bo Qiu ◽  
Xiulin Ruan
Keyword(s):  
Thin Films ◽  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Temperature Dependence ◽  
Thermal Transport ◽  
Room Temperature ◽  
Phonon Scattering ◽  
Md Simulations ◽  
Boundary Scattering ◽  
Nanoporous Films

In this work, thermal conductivity of perfect and nanoporous few-quintuple Bi2Te3 thin films as well as nanoribbons with perfect and zig-zag edges is investigated using molecular dynamics (MD) simulations with Green-Kubo method. We find minimum thermal conductivity of perfect Bi2Te3 thin films with three quintuple layers (QLs) at room temperature, and we believe it originates from the interplay between inter-quintuple coupling and phonon boundary scattering. Nanoporous films and nanoribbons are studied for additional phonon scattering channels in suppressing thermal conductivity. With 5% porosity in Bi2Te3 thin films, the thermal conductivity is found to decrease by a factor of 4–6, depending on temperature, comparing to perfect single QL. For nanoribbons, width and edge shape are found to strongly affect the temperature dependence as well as values of thermal conductivity.

Modelling of Thermal Rectification in Si and Ge Thin Films

2013 ◽  
Author(s):  
E. Chávez-Ángel ◽  
C. M. Sotomayor Torres ◽  
F. Alzina
Keyword(s):  
Thin Films ◽  
Thermal Conductivity ◽  
Heat Flow ◽  
Temperature Dependence ◽  
Cross Section ◽  
Impurity Concentration ◽  
Boundary Scattering ◽  
Bulk Materials ◽  
Thermal Rectification ◽  
Scattering Effects

In the present work we have studied an extension of the classical thermal rectification, arising in certain cases from the contact of two dissimilar bulk materials with different temperature dependence of the thermal conductivity, to the Si-Ge system when boundary scattering effects are taken into account. Moreover, the directionality of the in-plane heat flow in a Si plate can be achieved by tuning the thickness and the impurity concentration along the cross section of the plate. We have designed several potential structures with this function in mind and discussed the physics behind.

Effect of Hydrogen Passivation on the Thermal Conductivity of Nanoporous Crystalline Silicon: A Molecular Dynamics Study

2012 ◽  
Author(s):  
Jin Fang ◽  
Laurent Pilon
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Phonon Scattering ◽  
Crystalline Silicon ◽  
Scaling Law ◽  
Interfacial Area ◽  
Md Simulations ◽  
Hydrogen Passivation ◽  
Interfacial Area Concentration ◽  
Passivated Silicon

Effect of hydrogen passivation on thermal conductivity of nanoporous crystalline silicon was investigated using equilibrium molecular dynamics (MD) simulations from 500 to 1000 K. The porosity varied from 8% to 38% while the pore diameter ranged from 1.74 to 2.93 nm. Hydrogen passivation of the pore surface was found to reduce thermal conductivity by about 20% at 500 K due to enhanced phonon scattering by the passivated atoms at the nanopore surface. The effect of passivation diminished with increasing temperature. In fact, the phonon density of states at high temperatures was similar for both passivated and unpassivated silicon atoms. Finally, the thermal conductivity k was found to be linearly proportional to (1–1.5fv)/(Ai/4) where fv is the porosity and Ai is the pore interfacial area concentration. This scaling law was previously established for un-passivated silicon using non-equilibrium MD simulations.

Predicting Thermal Transport in Bi2Te3: From Bulk to Nanostructures

2011 ◽  
Vol 1329 ◽  
Author(s):  
Bo Qiu ◽  
Xiulin Ruan
Keyword(s):  
Experimental Data ◽  
Thin Films ◽  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Thermal Transport ◽  
Morse Potential ◽  
Density Functional ◽  
Energy Surface ◽  
Nanowire Diameter ◽  
Potential Form

ABSTRACTTwo-body interatomic potentials in the Morse potential form have been developed for bismuth telluride, and the potentials are used in molecular dynamics (MD) simulations to predict the thermal conductivity of Bi2Te3 bulk, nanowires and few-quintuple thin films. The density functional theory with local density approximations is first used to calculate the total energies for many artificially distorted Bi2Te3 configurations to produce the energy surface. Then by fitting to this energy surface and other experimental data, the Morse potential form is parameterized. Molecular dynamics simulations are then performed to predict the thermal conductivity of bulk Bi2Te3 at different temperatures, and the results agree with experimental data well. We also predicted the thermal conductivity of Bi2Te3 nanowires with diameter ranging from 3 to 30 nm with both smooth (SMNW) and rough (STNW) surfaces. It is found that when the nanowire diameter decreases to the molecular scale (below 10 nm, or the so called "quantum wire"), the thermal conductivity shows significant reduction as compared to bulk value. We find the dimensional crossover behavior of thermal transport in few quintuple layer (QL) thin films at room temperature, and we attribute it to the interplay between phonon Umklapp scattering and boundary scattering. Also, nanoporous films show significantly reduced thermal conductivity compared to perfect thin films, indicating that they can be very promising thermoelectric materials.

The Effects of Diameter and Chirality in the Thermal Transport in Free-Standing and Supported Carbon-Nanotubes

2012 ◽  
Author(s):  
Bo Qiu ◽  
Yan Wang ◽  
Qing Zhao ◽  
Xiulin Ruan
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Thermal Transport ◽  
Lattice Thermal Conductivity ◽  
Axial Direction ◽  
Md Simulations ◽  
Phonon Transport ◽  
Free Standing ◽  
Effective Boundary ◽  
Phonon Lifetime

We use molecular dynamics (MD) simulations to explore the lattice thermal transport in freestanding and supported single-wall carbon-nanotube (SWCNT) in comparison to that in graphene nanoribbon (GNR) and graphene sheet. We find the lattice thermal conductivity of freestanding SWCNT and GNR increases with diameter/width and approaches that of graphene. This is partly attributed to the curvature that shortens phonon lifetime in SWCNT. In contrast to GNR, there is only weak chirality dependence in the thermal conductivity of freestanding SWCNT. When SWCNT is put on substrate, an effective boundary along the SWCNT axial direction at the SWCNT-substrate interface is created, rendering resemblance between the phonon transport in supported SWCNT and that in freestanding GNR. As a result, the thermal conductivity of supported SWCNTs differ by around 10%, depending on chirality. The thermal conductivity of SWCNT decreases by about 34–41% when supported, which is less than that of the reduction seen in supported graphene.

Molecular Dynamics Simulations of Thermal Conductivity of Bi2Te3 Nanowires

2009 ◽  
Author(s):  
Bo Qiu ◽  
Lin Sun ◽  
Xiulin Ruan
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Surface Roughness ◽  
Smooth Surface ◽  
Lattice Thermal Conductivity ◽  
Phonon Scattering ◽  
Md Simulations ◽  
Interatomic Potentials ◽  
Phonon Confinement ◽  
Dynamics Simulations

In this paper, by employing the previously developed two-body interatomic potentials for bismuth telluride, molecular dynamics (MD) simulations are used to describe the thermoelectric properties, namely the lattice thermal conductivity, of Bi2Te3 nanowires. Cylindrical nanowires with both smooth surface and sawtooth surface roughness are studied, aiming at revealing the effects of phonon confinement in 1-D structures, phonon boundary scatterings and surface roughness on the lattice thermal conductivity of Bi2Te3 nanowires. In the end, the influence of various phonon scattering mechanisms on the nanostructures under study are summarized, possible paths to reduce lattice thermal conductivity in nanostructured Bi2Te3, which is favorable for enhancing thermoelectric performance, are pointed out.

Electron–phonon scattering effect on the lattice thermal conductivity of silicon nanostructures

2017 ◽  
Vol 19 (42) ◽  
pp. 28517-28526 ◽  
Author(s):  
Bo Fu ◽  
Guihua Tang ◽  
Yifei Li
Keyword(s):  
Thin Films ◽  
Thermal Conductivity ◽  
Thermal Transport ◽  
Lattice Thermal Conductivity ◽  
Phonon Scattering ◽  
Silicon Nanostructures ◽  
Nanoscale Thermal Transport ◽  
Scattering Effect ◽  
Solid Thin Films ◽  
Electron Phonon Scattering

The effect of electron–phonon scattering on the nanoscale thermal transport is investigated systematically in nanowires, solid thin films and nanoporous thin films by considering the phonon–phonon, phonon–boundary and electron–phonon scattering simultaneously.

scholarly journals Thermal Conductivities of Crosslinked Polyisoprene and Polybutadiene from Molecular Dynamics Simulations

Polymers ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 315
Author(s):  
Aleksandr Vasilev ◽  
Tommy Lorenz ◽  
Cornelia Breitkopf
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Temperature Dependence ◽  
Molecular Dynamics Simulations ◽  
Md Simulations ◽  
Dynamics Simulations ◽  
First Time ◽  
Soft Rubber ◽  
Good Agreement ◽  
Thermal Conductivities

For the first time, the thermal conductivities of vulcanized polybutadiene and polyisoprene have been investigated according to their degree of crosslinking. The C-C and C-S-S-C crosslink bridges, which can be obtained via vulcanization processes using peroxides and sulfur, respectively, are considered. The temperature dependence of the thermal conductivity of soft rubber derived from molecular dynamics (MD) simulations is in very good agreement with the experimental results. The contributions of bonded and non-bonded interactions in the MD simulations and their influence on the thermal conductivities of polyisoprene and polybutadiene are presented. The details are discussed in this paper.

A Molecular Dynamics Study of Thermal Conductivity in Nanocomposites via the Phonon Wave Packet Method

2009 ◽  
Author(s):  
Zhiting Tian ◽  
Sang Kim ◽  
Ying Sun ◽  
Bruce White
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Wave Packet ◽  
Molecular Dynamics Simulations ◽  
Phonon Scattering ◽  
Flow Direction ◽  
Normal Incidence ◽  
Material Interfaces ◽  
Non Equilibrium Molecular Dynamics ◽  
Dynamics Simulations

The phonon wave packet technique is used in conjunction with the molecular dynamics simulations to directly observe phonon scattering at material interfaces. The phonon transmission coefficient of nanocomposites is examined as a function of the defect size, thin film thickness, orientation of interface to the heat flow direction. To generalize the results based on phonons in a narrow frequency range and at normal incidence, the effective thermal conductivity of the same nanocomposite structure is calculated using non-equilibrium molecular dynamics simulations for model nanocomposites formed by two mass-mismatched Ar-like solids and heterogeneous Si-SiCO2 systems. The results are compared with the modified effective medium formulation for nanocomposites.

Long-term Room Temperature Instability in Thermal Conductivity of InGaZnO Thin Films

MRS Advances ◽  
2016 ◽  
Vol 1 (22) ◽  
pp. 1631-1636 ◽  
Author(s):  
Boya Cui ◽  
D. Bruce Buchholz ◽  
Li Zeng ◽  
Michael Bedzyk ◽  
Robert P. H. Chang ◽  
...  
Keyword(s):  
Thin Films ◽  
Thermal Conductivity ◽  
Room Temperature ◽  
Storage Time ◽  
Laser Deposition ◽  
Low Oxygen ◽  
X Ray Diffraction ◽  
3Ω Method ◽  
X Ray

ABSTRACTThe cross-plane thermal conductivities of InGaZnO (IGZO) thin films in different morphologies were measured on three occasions within 19 months, using the 3ω method at room temperature 300 K. Amorphous (a-), semi-crystalline (semi-c-) and crystalline (c-) IGZO films were grown by pulsed laser deposition (PLD), followed by X-ray diffraction (XRD) for evaluation of film quality and crystallinity. Semi-c-IGZO shows the highest thermal conductivity, even higher than the most ordered crystal-like phase. After being stored in dry low-oxygen environment for months, a drastic decrease of semi-c-IGZO thermal conductivity was observed, while the thermal conductivity slightly reduced in c-IGZO and remained unchanged in a-IGZO. This change in thermal conductivity with storage time can be attributed to film structural relaxation and vacancy diffusion to grain boundaries.

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