Elastic properties and lattice thermal conductivity of amorphous Ge2Sb2Te5 and GeTe thin films

2021 ◽  
Vol 129 (13) ◽  
pp. 135102
Author(s):  
M. Baloi ◽  
D. Wamwangi ◽  
B. A. Mathe ◽  
R. M. Erasmus ◽  
D. G. Billing ◽  
...  
Keyword(s):  
Thin Films ◽  
Thermal Conductivity ◽  
Elastic Properties ◽  
Lattice Thermal Conductivity

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

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.

Development of an Ab-initio Model of the Lattice Thermal Conductivity in Semiconductor Thin Films and Nanowires

2001 ◽  
Vol 677 ◽  
Author(s):  
Jie Zou ◽  
Alexander Balandin
Keyword(s):  
Thin Films ◽  
Thermal Conductivity ◽  
Lattice Thermal Conductivity ◽  
Phonon Dispersion ◽  
Interface Roughness ◽  
Semiconductor Thin Films ◽  
Predicted Values ◽  
Rough Boundaries ◽  
Good Agreement ◽  
Non Equilibrium

ABSTRACTA model for calculating the lattice thermal conductivity in semiconductor thin films and nanowires is developed. It is based on the solution of phonon Boltzmann equation and takes into account phonon dispersion modification due to confinement effects and non-equilibrium phonon redistribution. Phonon spatial confinement at the structure boundaries leads to modification of the acoustic phonon dispersion and corresponding drop in the mode-averaged group velocity. Scattering from rough boundaries and interfaces introduces a change in the non-equilibrium phonon distribution as compared to bulk. These effects lead to a reduction in the in-plane lattice thermal conductivity in both thin films and nanowires. The predicted values for the lattice thermal conductivity and their temperature and interface roughness dependence are in good agreement with available experimental data.

scholarly journals First-Principles Study of Structure, Elastic Properties, and Thermal Conductivity of Monolayer Calcium Hydrobromide

2021 ◽  
Vol 2021 ◽  
pp. 1-7
Author(s):  
Si-Hua Li ◽  
Cui-E Hu ◽  
Xiao-Lu Wang ◽  
Yan Cheng
Keyword(s):  
Thermal Conductivity ◽  
Elastic Properties ◽  
First Principles ◽  
Lattice Thermal Conductivity ◽  
Mechanical Stability ◽  
Iterative Solution ◽  
Mean Free Path ◽  
Hydrogen Atmosphere ◽  
Theoretical Studies ◽  
Boltzmann Transport

In recent years, some laboratories have been able to prepare calcium hydrobromide (CaHBr) by melting hydride and anhydrous bromide or metal and bromide in a hydrogen atmosphere at 900°C and have studied some of its properties. But there are few theoretical studies, especially the theoretical studies of monolayer CaHBr. We use the first-principles method to calculate the structure, elastic properties, and lattice thermal conductivity of the monolayer CaHBr based on the Boltzmann transport equation. We obtain a stable crystal structure by the optimization of monolayer CaHBr. By calculating the elastic constant of monolayer CaHBr, its mechanical stability is proved, and the elastic limit of monolayer CaHBr is obtained by biaxial tensile strain on monolayer CaHBr. And the corresponding phonon spectra show no imaginary frequency, indicating the dynamic stability of the monolayer CaHBr. By the ShengBTE code, we calculate the lattice thermal conductivity of the monolayer CaHBr, the iterative solution of BTE and RTA at 300 K–1200 K is obtained, and the lattice thermal conductivity at room temperature is κ ι BTE = 2.469   W / m ⋅ K and κ ι RTA = 2.201   W / m ⋅ K , respectively. It can be seen that the lattice thermal conductivity of monolayer CaHBr is low. And by analyzing the phonon spectrum, the scattering rate, and the mean free path of the phonons, the lattice thermal conductivity of monolayer CaHBr mainly depends on the acoustic modes. We hope this study can provide theoretical guidance for the experiments and practical application of monolayer CaHBr.

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