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.

Physical properties of chalcopyrite-type Cu1−xAgxGaTe2 by first-principles study

2016 ◽  
Vol 30 (30) ◽  
pp. 1650373 ◽  
Author(s):  
Li Xue ◽  
Yi-Ming Ren ◽  
Zheng-Long Hu
Keyword(s):  
Thermal Conductivity ◽  
Elastic Constants ◽  
Density Functional ◽  
Lattice Thermal Conductivity ◽  
Lattice Parameter ◽  
Functional Theory ◽  
Lattice Volume ◽  
Te Material ◽  
Ag Substitution ◽  
Good Agreement

[Formula: see text] is a promising thermoelectric (TE) material for high temperature TE applications. This work systematically investigated the structural, elastic and thermodynamic properties of [Formula: see text] ([Formula: see text] = 0, 0.25, 0.5, 0.75 and 1) by density functional theory. The calculated lattice volume is expanded with the increase of Ag content, but this expansion is anisotropic. The lattice parameter along [Formula: see text]-axis is linear expansion, and along [Formula: see text]-axis is parabolic expansion, which is in good agreement with available experimental data. The phase stability of [Formula: see text] alloy is studied by analyzing the formation energy, cohesive energy and elastic constants. Shear modulus, Young’s modulus, sound velocities, Debye temperature and the minimum thermal conductivity are obtained from the calculated elastic constants. The results show that Ag substitution could reduce the lattice thermal conductivity, which is helpful for improving the TE properties of [Formula: see text].

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.

PHONON HEAT CONDUCTIVITY OF InSb AND CdS

2011 ◽  
Vol 25 (10) ◽  
pp. 1409-1418 ◽  
Author(s):  
M. ATAULLAH ANSARI ◽  
VINOD ASHOKAN ◽  
B. D. INDU
Keyword(s):  
Thermal Conductivity ◽  
Heat Conductivity ◽  
Lattice Thermal Conductivity ◽  
Relaxation Times ◽  
Temperature Range ◽  
Callaway Model ◽  
Theory And Experiments ◽  
Good Agreement

The lattice thermal conductivity of InSb and CdS has been analyzed on the basis of the most acquiescent Callaway model in the temperature range 2–300.779 K and 2.296–283.565 K. To reinvigorate the effects of phonon anharmonicities, more rigorous expressions for the phonon–phonon interactions, resonance, impurity and interference scattering relaxation times have been introduced to theoretically justify the experimentally observed results. A fairly good agreement between theory and experiments has been presented.

Pit nucleation in compound semiconductor thin films

2003 ◽  
Vol 794 ◽  
Author(s):  
Mathieu Bouville ◽  
Michael L. Falk ◽  
Joanna Mirecki Millunchick
Keyword(s):  
Thin Films ◽  
Three Dimensional ◽  
Growth Conditions ◽  
Compound Semiconductor ◽  
Nucleation Process ◽  
Stages Of Growth ◽  
Semiconductor Thin Films ◽  
Experimental Parameters ◽  
Pit Nucleation ◽  
Good Agreement

ABSTRACTPit nucleation has been observed in a variety of semiconductor thin films. We present a model in which pit nucleation is considered to arise from a near-equilibrium nucleation process in which the adatom concentration plays an important role. Although pits relieve elastic energy more efficiently than islands, pit nucleation is prevented if the adatom concentration is too high. Inhomogeneities in the adatom density on the surface due to three-dimensional islands enhance pit nucleation. Thermodynamic considerations predict several different growth regimes in which pits may nucleate at different stages of growth depending on the materials system and growth conditions. However kinetics must be taken into account to make direct comparisons to experimental observations. These comparisons show good agreement given the uncertainties in quantifying experimental parameters such as the surface energy.

Lattice Boltzmann Modeling of Subcontinuum Energy Transport in Crystalline and Amorphous Microelectronic Devices

2006 ◽  
Vol 128 (2) ◽  
pp. 115-124 ◽  
Author(s):  
Rodrigo Escobar ◽  
Brian Smith ◽  
Cristina Amon
Keyword(s):  
Thin Films ◽  
Thermal Conductivity ◽  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Energy Transport ◽  
Phonon Dispersion ◽  
Numerical Models ◽  
Phonon Transport ◽  
Nonlinear Frequency ◽  
Boltzmann Method

Numerical simulations of time-dependent energy transport in semiconductor thin films are performed using the lattice Boltzmann method applied to phonon transport. The discrete lattice Boltzmann method is derived from the continuous Boltzmann transport equation assuming first gray dispersion and then nonlinear, frequency-dependent phonon dispersion for acoustic and optical phonons. Results indicate that a transition from diffusive to ballistic energy transport is found as the characteristic length of the system becomes comparable to the phonon mean free path. The methodology is used in representative microelectronics applications covering both crystalline and amorphous materials including silicon thin films and nanoporous silica dielectrics. Size-dependent thermal conductivity values are also computed based on steady-state temperature distributions obtained from the numerical models. For each case, reducing feature size into the subcontinuum regime decreases the thermal conductivity when compared to bulk values. Overall, simulations that consider phonon dispersion yield results more consistent with experimental correlations.

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