Thermal Resistance of Silicon/Germanium Interfaces From Lattice Dynamics Calculations

2009 ◽  
Author(s):  
E. S. Landry ◽  
A. J. H. McGaughey
Keyword(s):  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Energy Conversion ◽  
Silicon Germanium ◽  
Lattice Dynamics ◽  
Phonon Scattering ◽  
Semiconductor Interfaces ◽  
Thermoelectric Energy ◽  
Interface Scattering ◽  
Computer Chips

Phonon scattering at the interface between two materials results in a thermal resistance, R [1]. An ability to accurately predict the thermal resistance of semiconductor interfaces is important in devices where phonon interface scattering is a significant contributor to the overall thermal resistance (e.g., computer chips with high component density). This ability will also lead to improvements in the design of semiconductor superlattices with low thermal conductivity, desirable in thermoelectric energy conversion applications [2].

Predicting the Thermal Boundary Resistance of Isolated and Closely-Spaced Si/Si1−XGeX Interfaces With Molecular Dynamics Simulations

2008 ◽  
Author(s):  
E. S. Landry ◽  
T. Matsuura ◽  
A. J. H. McGaughey
Keyword(s):  
Phonon Scattering ◽  
Temperature Drop ◽  
Nanocomposite Materials ◽  
Boundary Resistance ◽  
Thermal Boundary Resistance ◽  
Semiconductor Interfaces ◽  
Thermoelectric Energy ◽  
Interface Scattering ◽  
Computer Chips ◽  
Dynamics Simulations

Phonon scattering at an interface between two materials results in a thermal boundary resistance R, given by [1] R=ΔTq,(1) where ΔT and q are the temperature drop and heat flux across the interface. Predicting the thermal boundary resistance of semiconductor/semiconductor interfaces is important in devices where phonon interface scattering is a significant contributor to the overall thermal resistance (e.g., computer chips with high component density). Such predictions will also lead to improvements in the design of nanocomposite materials (e.g., superlattices) with low thermal conductivity, desirable in thermoelectric energy conversion applications [2].

Thermal Conductivity of One-Dimensional Silicon-Germanium Alloy Nanowires

2009 ◽  
Author(s):  
Yunki Gwak ◽  
Vinay Narayanunni ◽  
Sang-Won Jee ◽  
Anastassios A. Mavrokefalos ◽  
Michael T. Pettes ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Energy Conversion ◽  
Silicon Germanium ◽  
Figure Of Merit ◽  
Mean Free Path ◽  
Thermoelectric Efficiency ◽  
One Dimensional ◽  
Thermoelectric Energy ◽  
Germanium Alloy ◽  
Alloy Nanowires

Thermal properties of one dimensional nanostructures are of interest for thermoelectric energy conversion. Thermoelectric efficiency is related to non dimensional thermoelectric figure of merit, ZT = (S^2 σT)/k where S, σ, k are the Seebeck coefficient, electrical conductivity and thermal conductivity respectively. These physical properties are interdependent, and hence making ZT of a material high is very challenging work. However, when the size of nanostructure is comparable to the wavelength and mean free path of energy carriers, it is feasible to avoid such interdependence to enhance ZT energy conversion. [1–3]

scholarly journals Anomalous thermal conductivity enhancement in low dimensional resonant nanostructures due to imperfections

Nanoscale ◽  
2021 ◽  
Author(s):  
Hongying Wang ◽  
Yajuan Cheng ◽  
Zheyong Fan ◽  
Yangyu Guo ◽  
Zhongwei Zhang ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Energy Conversion ◽  
Thermal Conductivity Enhancement ◽  
Heat Management ◽  
Thermoelectric Energy Conversion ◽  
Conductivity Enhancement ◽  
Thermoelectric Energy ◽  
Low Dimensional

Nanophononic metamaterials have broad applications in fields such as heat management, thermoelectric energy conversion, and nanoelectronics. Phonon resonance in pillared low-dimensional structures has been suggested to be a feasible approach...

Thermoelectric Transport in Silicon Germanium Nanocomposite

2008 ◽  
Author(s):  
Hohyun Lee ◽  
Daryoosh Vashaee ◽  
Xiaowei Wang ◽  
Giri Joshi ◽  
Gaohua Zhu ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Energy Conversion ◽  
Silicon Germanium ◽  
Figure Of Merit ◽  
Waste Heat ◽  
Electrical Energy ◽  
Energy Conversion Efficiency ◽  
Thermoelectric Effects ◽  
Thermoelectric Transport ◽  
Potential Applications

Direct energy conversion between heat and electrical energy based on thermoelectric effects is attractive for potential applications in waste heat recovery and environmentally-friendly refrigeration. The energy conversion efficiency depends on the dimensionless figure of merit of thermoelectric materials, ZT, which is proportional to the electrical conductivity, the square of the Seebeck coefficient, and the inverse of the thermal conductivity. Currently, the low ZT values of available materials restrict the applications of this technology. However, significant enhancements in ZT were recently reported in nanostructured materials such as superlattices mainly due to their low thermal conductivities. According to recent studies, the reduced thermal conductivity of nanostructures is attributed to the large number of interfaces at which phonons are scattered. Based on this idea, nanocomposites are expected to have a lower thermal conductivity than their bulk counterparts with low fabrication cost just by mixing nano sized particles. In this work, we will discuss mechanisms of thermoelectric transport via modeling and provide experimental evidence on the enhancement of thermoelectric figure of merit in SiGe-based nanocomposites.

scholarly journals Ultra-low Thermal Conductivity in Si/Ge Hierarchical Superlattice Nanowire

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
Xin Mu ◽  
Lili Wang ◽  
Xueming Yang ◽  
Pu Zhang ◽  
Albert C. To ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Silicon Germanium ◽  
Phonon Scattering ◽  
Low Thermal Conductivity ◽  
Structural Hierarchy ◽  
Si Nanowire ◽  
Hierarchical Structuring ◽  
Simulation Results ◽  
Dynamics Simulations

Abstract Due to interfacial phonon scattering and nanoscale size effect, silicon/germanium (Si/Ge) superlattice nanowire (SNW) can have very low thermal conductivity, which is very attractive for thermoelectrics. In this paper, we demonstrate using molecular dynamics simulations that the already low thermal conductivity of Si/Ge SNW can be further reduced by introducing hierarchical structure to form Si/Ge hierarchical superlattice nanowire (H-SNW). The structural hierarchy introduces defects to disrupt the periodicity of regular SNW and scatters coherent phonons, which are the key contributors to thermal transport in regular SNW. Our simulation results show that periodically arranged defects in Si/Ge H-SNW lead to a ~38% reduction of the already low thermal conductivity of regular Si/Ge SNW. By randomizing the arrangement of defects and imposing additional surface complexities to enhance phonon scattering, further reduction in thermal conductivity can be achieved. Compared to pure Si nanowire, the thermal conductivity reduction of Si/Ge H-SNW can be as large as ~95%. It is concluded that the hierarchical structuring is an effective way of reducing thermal conductivity significantly in SNW, which can be a promising path for improving the efficiency of Si/Ge-based SNW thermoelectrics.

scholarly journals Термоэлектрические свойства полуметаллических и полупроводниковых фольг и нитей Bi-=SUB=-1-x-=/SUB=-Sb-=SUB=-x-=/SUB=-

2019 ◽  
Vol 53 (5) ◽  
pp. 664
Author(s):  
А. Николаева ◽  
Л. Конопко ◽  
И. Гергишан ◽  
К. Рогацкий ◽  
П. Стачовик ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Low Temperatures ◽  
Phonon Scattering ◽  
Surface States ◽  
Experimental Investigations ◽  
Quantum Size ◽  
Thermoelectric Energy ◽  
Conductive Surface ◽  
Order Of Magnitude

AbstractThe results of experimental investigations into the thermoelectric properties (electrical conductivity, thermoelectric power, and thermal conductivity) of microtextured foils and single-crystal wires based on semimetal and semiconductor Bi_1 –_ x Sb_ x alloys are presented in the temperature range of 4.2–300 K. It is found that the band gap Δ E in Bi–17 at % Sb wires increases with decreasing wire diameter d , which is a manifestation of the quantum-size effect. At low temperatures ( T < 50 K), in the wires with d < 400 nm, the electrical conductivity increases due to the significant contribution of highly conductive surface states characteristic of topological insulators. It is found for the first time that the thermal conductivity of semimetal Bi–3 at % Sb foils at low temperatures is two orders of magnitude lower, and that of semiconductor Bi–16 at % Sb foils one order of magnitude lower, than that in bulk samples of the corresponding composition due to significant phonon scattering at grain boundaries and surfaces. This effect leads to considerable enhancement of the thermoelectric figure-of-merit ZT and can be used in miniature low-temperature thermoelectric energy converters.

Translation-rotation coupling and heat transfer in orientationally-disordered phase of CCl4

Open Physics ◽  
2006 ◽  
Vol 4 (2) ◽  
Author(s):  
Oleg Pursky ◽  
Vyacheslav Konstantinov
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Free Path ◽  
Phonon Scattering ◽  
Mean Free Path ◽  
Mobility Edge ◽  
Total Thermal Resistance ◽  
Disordered Phase ◽  
Diffusive Modes

AbstractThe isochoric thermal conductivity of an orientationally-disordered phase of CCl4 is analysed within a model in which heat is transferred by phonons and above the phonon mobility edge by ”diffusive” modes migrating randomly from site to site. The mobility edge ω0 is found from the condition that the phonon mean-free path cannot become smaller than half the phonon wavelength. The contributions of phonon-phonon, one-, and two-phonon scattering to the total thermal resistance of solid CCl4 are calcualted under the assumption that the different scattering mechanisms contribute additively. An increase in the isochoric thermal conductivity with temperature is explained by suppression of phonon scattering at rotational excitations due to a decrease in correlation in the rotation of neighbouring molecules.

Lattice Dynamics Study of Anisotropic Heat Conduction in Superlattices

2000 ◽  
Vol 626 ◽  
Author(s):  
B. Yang ◽  
G. Chen
Keyword(s):  
Thermal Conductivity ◽  
Group Velocity ◽  
Lattice Dynamics ◽  
Phonon Scattering ◽  
Diffuse Interface ◽  
Phonon Confinement ◽  
Dynamics Model ◽  
Phonon Group Velocity ◽  
Anisotropic Heat Conduction ◽  
The Cross

ABSTRACTPast studies on the thermal conductivity suggest that phonon confinement and the associated group velocity reduction are the causes of the observed drop in the cross-plane thermal conductivity of semiconductor superlattices. In this work, we investigate the contribution of phonon confinement to the in-plane thermal conductivity of superlattices and the anisotropic effects of phonon confinement on the thermal conductivity in different directions, using a lattice dynamics model. We find that the reduced phonon group velocity due to phonon confinement may account for the dramatic reduction in the cross-plane thermal conductivity, but the in-plane thermal conductivity drop, caused by the reduced group velocity, is much less than the reported experimental results. This suggests that the reduced relaxation time due to diffuse interface phonon scattering, dislocation scattering, etc, should make major contribution to the in-plane thermal conductivity reduction.

Modeling of Strain-Induced Phonon Thermal Conductivity Reduction in Thermoelectric Nanocomposites

2008 ◽  
Author(s):  
Yaoyao Xu ◽  
Gang Li
Keyword(s):  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Lattice Dynamics ◽  
Tensile Strain ◽  
Phonon Scattering ◽  
Mean Free Path ◽  
Nanocomposite Material ◽  
Phonon Thermal Conductivity ◽  
Strain Effects ◽  
Strain Dependent

In this paper, we study strain effects on the phonon thermal conductivity of 2-D Si/Ge nanocomposites. Lattice dynamics is employed for the calculation of the phonon scattering properties as a function of strain. Cauchy-Born rule is used to model the deformed configuration of the atoms. The effective thermal conductivity of the nanocomposite material is modeled by using a modified effective medium approximation (EMA) approach. The strain effects are incorporated into the modified EMA through the strain dependent phonon mean free path. The effective thermal conductivity of the strained nanocomposite material is calculated for different characteristic lengths of the Si component. The results show that a 2% tensile strain can reduce the effective thermal conductivity by more than 10%.

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