Thermal Interface Resistances in Nanostructures

2007 ◽  
Author(s):  
Matthew Panzer ◽  
Ken Goodson
Keyword(s):  
Heat Conduction ◽  
Thermal Conduction ◽  
Photonic Devices ◽  
Square Lattice ◽  
Phonon Confinement ◽  
Phonon Modes ◽  
Material Interfaces ◽  
Acoustic Mismatch ◽  
The Impact ◽  
Abrupt Junction

Nanostructured electronic and photonic devices include a high density of material interfaces, which can strongly impede heat conduction and influence performance and reliability. Thermal conduction through interfaces is a very mature field as long as the interface dimensions are large compared to the phonon wavelength. In nanostructures, however, the confinement of phonons in the directions parallel to the interface may strongly influence heat conduction. The present work investigates a model problem consisting of an abrupt junction between a harmonic 1D and 2D square lattice. The results show that energy couples to phonon modes localized near the free surface and that the energy transmission coefficient across the interface into these surface modes is less than unity even for materials with identical bulk impedances. The lattice dynamics calculations performed here provide an initial perspective on the impact of phonon confinement on the acoustic mismatch resistance and lay the groundwork for more detailed studies involving 3D molecular dynamics.

scholarly journals The Impact of Vibrational Entropy on the Segregation of Cu to Antiphase Boundaries in Fe3Al

2021 ◽  
Vol 7 (8) ◽  
pp. 108
Author(s):  
Martin Friák ◽  
Miroslav Černý ◽  
Mojmír Šob
Keyword(s):  
Magnetic Moments ◽  
Energy Difference ◽  
Extended Defects ◽  
Vibrational Entropy ◽  
Phonon Modes ◽  
Antiphase Boundaries ◽  
Related Energy ◽  
Quantum Mechanical Study ◽  
Nonlinear Trends ◽  
The Impact

We performed a quantum mechanical study of segregation of Cu atoms toward antiphase boundaries (APBs) in Fe3Al. The computed concentration of Cu atoms was 3.125 at %. The APBs have been characterized by a shift of the lattice along the ⟨001⟩ crystallographic direction. The APB energy turns out to be lower for Cu atoms located directly at the APB interfaces and we found that it is equal to 84 mJ/m2. Both Cu atoms (as point defects) and APBs (as extended defects) have their specific impact on local magnetic moments of Fe atoms (mostly reduction of the magnitude). Their combined impact was found to be not just a simple sum of the effects of each of the defect types. The Cu atoms are predicted to segregate toward the studied APBs, but the related energy gain is very small and amounts to only 4 meV per Cu atom. We have also performed phonon calculations and found all studied states with different atomic configurations mechanically stable without any soft phonon modes. The band gap in phonon frequencies of Fe3Al is barely affected by Cu substituents but reduced by APBs. The phonon contributions to segregation-related energy changes are significant, ranging from a decrease by 16% at T = 0 K to an increase by 17% at T = 400 K (changes with respect to the segregation-related energy difference between static lattices). Importantly, we have also examined the differences in the phonon entropy and phonon energy induced by the Cu segregation and showed their strongly nonlinear trends.

scholarly journals Design and Implementation of a Laboratory Equipment for Studying Heat Transfer by Conduction

2019 ◽  
Vol 11 (1) ◽  
pp. 153-156
Author(s):  
István Padrah ◽  
Judit Pásztor ◽  
Rudolf Farmos
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Conduction ◽  
Thermal Conduction ◽  
Transfer Mechanism ◽  
Measuring Instrument ◽  
Heat Transfer Mechanism ◽  
Laboratory Equipment ◽  
Insulating Materials ◽  
Design And Implementation

Abstract Thermal conduction is a heat transfer mechanism. It is present in our everyday lives. Studying thermal conductivity helps us better understand the phenomenon of heat conduction. The goal of this paper is to measure the thermal conductivity of various materials and compare results with the values provided by the manufacturers. To achieve this we assembled a measuring instrument and performed measurements on heat insulating materials.

scholarly journals 2D MHD Simulations of the State Transitions of X-Ray Binaries Taking into Account Thermal Conduction

Galaxies ◽  
2019 ◽  
Vol 7 (1) ◽  
pp. 22 ◽  
Author(s):  
Kenji E. Nakamura ◽  
Mami Machida ◽  
Ryoji Matsumoto
Keyword(s):  
Black Hole ◽  
Heat Conduction ◽  
High Temperature ◽  
Temperature Region ◽  
Thermal Conduction ◽  
State Transitions ◽  
Intermediate Region ◽  
Accretion Flows ◽  
Cool Flow ◽  
Hot Corona

Thermal conduction plays an important role in bimodal accretion flows consisting of high-temperature flow and cool flow, especially when the temperature is high and/or has a steep gradient. For example, in hard-to-soft transitions of black hole accretion flows, thermal conduction between the high-temperature region and the low-temperature region is appropriately considered. We conducted two-dimensional magnetohydrodynamic (MHD) numerical simulations considering anisotropic heat conduction to study condensation of geometrically thick hot accretion flows driven by radiative cooling during state transitions. Numerical results show that the intermediate region appears between the hot corona and the cool accretion disk when we consider heat conduction. The typical temperature and number density of the intermediate region of the 10 Mo black hole at 10Rg (Rg = 3.0 x 106 cm is the Schwarzschild radius) are 4 x 1010 < T [K] < 4 x 1012 and 5 x 1015 < n [cm-3] < 5 x 1717, respectively. The thickness of intermediate region is about half of the radius. By comparing two models with or without thermal conduction, we demonstrate the effects of thermal conduction.

Simulations of Deformation and Stress During Copper Wirebond on ULK Chips

2013 ◽  
Author(s):  
Hung-Yun Lin ◽  
Kritika Upreti ◽  
Allen Tippmann ◽  
Ganesh Subbarayan ◽  
Dae Young Jung ◽  
...  
Keyword(s):  
Crack Initiation ◽  
Ultrasonic Vibration ◽  
Partition Of Unity ◽  
Element Model ◽  
Material Interfaces ◽  
Critical States ◽  
Mechanical Responses ◽  
Hierarchical Partition ◽  
Damage Law ◽  
The Impact

In this paper, we develop a multi-level modeling procedure for copper wirebonding that provides insights into (a) deformation and stress in wire, pad, and die (b) an assessment of the risk of ULK fracture during impact stage and ultrasonic vibration steps. First, we construct a nonlinear, dynamic finite element model (global) to study the mechanical responses of wire, pad, and the underlying ULK stacks during the impact stage and the last cycle of ultrasonic vibration in copper wirebonding. Specifically, these process steps are modeled through prescribing touch down and in-plane oscillatory motions on capillary, which result in dissimilar critical states of stress locally in the ULK stacks. Next, we develop a isogeometric model (local) for a generic configuration of ULK stacks with eight levels of metallization by composing the geometric primitives representing ILD layers, copper lines/vias, as well as the material interfaces following the Hierarchical Partition of Unity Field Composition technique. The description for material moduli in the entire ULK stacks is further enriched with a bi-linear damage law. The critical states of stress obtained in the global wirebond model are then converted into boundary conditions for the local ILD model under plane strain condition to simulate the crack initiation in the ULK stacks. We observe, from the simulation results, potential crack initiation sites along vertical /horizontal interfaces in the ULK stacks due to local compressive/tensile loading during impact/vibration step, respectively.

Role of Variable Conductance on Heat and Mass Transport Mechanism Using Generalized Theory

2020 ◽  
Vol 13 (2) ◽  
Author(s):  
Imran Haider Qureshi ◽  
Ahmed Elmoasry ◽  
Jawdat Alebraheem ◽  
M. Nawaz
Keyword(s):  
Thermal Conductivity ◽  
Heat Conduction ◽  
Chemical Reaction ◽  
Diffusion Coefficients ◽  
Mass Diffusion ◽  
Memory Effects ◽  
Temperature Dependent ◽  
Newton's Law ◽  
Newton’S Law ◽  
The Impact

Abstract Fourier law of heat conduction, its analog Fick's first law, and Newton's law of viscosity are classical laws that are not capable of exhibiting memory effects. Conservation laws based on these classical laws do not give predictions about memory effects on the transport phenomena. Recently, proposed novel laws are called Cattaneo–Christov heat flux. Models are based on the generalization of classical laws of heat conduction, mass diffusion, and Newton's law of viscosity. This investigation considers this generalized theory to model the impact of relaxation phenomenon on the transport of momentum, heat, and mass in Maxwell fluid (viscoelastic fluid) of temperature-dependent viscosity and thermal conductivity in the presence of temperature-dependent mass diffusion coefficients. It is observed from the simulations that memory effects play a key role in controlling momentum, thermal and concentration boundary layer thicknesses. It is also noted that the rate of diffusion of heat and mass has shown an increasing trend when thermal conductivity and mass diffusion coefficients are increased via rise in temperature of the fluid. The generative chemical reaction on the transport of specie relative to the impact on the transport of specie when it is compared with the impact of destructive chemical reaction on the transport of specie.

Construction of a Broad-Based Experimental and Computational Test Capability for High Power Wide Bandgap Semiconductor Devices

2007 ◽  
Author(s):  
Jason A. Carter ◽  
Matthew D. Roth ◽  
Michael W. Horgan ◽  
Lisa Shellenberger ◽  
Daniel P. Hoffmann ◽  
...  
Keyword(s):  
Thermal Stresses ◽  
High Electron Mobility Transistors ◽  
Operating Conditions ◽  
High Electron ◽  
Thermal Impedance ◽  
Analysis Model ◽  
Operational Parameters ◽  
Material Interfaces ◽  
Electron Mobility Transistors ◽  
The Impact

In this paper, the authors will discuss the development and implementation of a test stand to assess the impact of temperature on the performance of commercial X-band gallium nitride (GaN) on silicon carbide (SiC) high electron mobility transistors (HEMTs) designed for radio frequency (RF) communications platforms. The devices are tested under a range of operating temperatures and under a range of electrical operating conditions of variable gate and source-drain voltages to assess the impact of temperature on core operational parameters of the device such as channel resistance and transconductance. This test capability includes infrared thermography and transient thermal impedance measurements of the device. In addition to the experimental effort, the initial construction of a finite-volume numerical analysis model of the device will be discussed. The focus of these models will be the accurate assessment of device thermal impedance based on assumed thermal loads and eventually the assessment of accumulated thermal stresses at the material interfaces within the device and package structure.

Two-dimensional hybrid analytical approach for the investigation of thermal aspects in human tissue undergoing regional hyperthermia therapy

2020 ◽  
Vol 234 (20) ◽  
pp. 3951-3966
Author(s):  
Jaideep Dutta ◽  
Balaram Kundu
Keyword(s):  
Heat Flux ◽  
Heat Conduction ◽  
Cancer Treatment ◽  
Thermal Response ◽  
Skin Tissue ◽  
Hyperbolic Heat Conduction ◽  
Two Dimensional ◽  
Regional Hyperthermia ◽  
Hyperthermia Therapy ◽  
The Impact

The formation of the present work is based on the development of the exact analytical solution of two-dimensional temperature response by employing the hyperbolic heat conduction bioheat model in a single-layered human skin tissue subjected to the regional hyperthermia therapy (RHT) for cancer treatment. The mathematical approach has been utilized as a hybrid form of ‘separation of variables’ and ‘finite integral transform’ method. Three kinds of surface heat fluxes (constant, sinusoidal and cosine) have been employed as an external heat source on the therapeutic surface of the square-shaped skin tissue of 100 mm × 100 mm. An innovative form of initial condition (spatially dependent) has been implemented in the present mathematical formulation as skin tissues are highly non-homogeneous and non-uniform in structure. The present research outcome indicates that cosine heat flux would be a suitable alternative for the sinusoidal heat flux. The impact of the relaxation time lag has been clearly noted in the thermal response with the waveform-like behaviour and it justifies the postulate of hyperbolic heat conduction. The two-dimensional temperature of the skin tissue has been observed in the range of 48.1 ℃–40 ℃ (in decreasing order). Estimated peak temperatures are in the proposed spectrum of hyperthermia therapy for an exposure time of 100 s, and this fact is true in an agreement with the medical protocol of the cancer treatment. The accuracy of the mathematical modelling and in-house computer codes are justified with the published numerical models and the maximum deviation of the thermal response has been noticed in order of 1.5–3%. The two-dimensional surface thermal contours have provided a glimpse of heat flow in the physical domain of skin tissue under different heating conditions and this research output may be beneficial to establish the theoretical standard of the regional hyperthermia treatment for cancer eradication.

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.

Refined bond-based peridynamics for thermal diffusion

2019 ◽  
Vol 36 (8) ◽  
pp. 2557-2587 ◽  
Author(s):  
Xin Gu ◽  
Qing Zhang ◽  
Erdogan Madenci
Keyword(s):  
Heat Conduction ◽  
Differential Operator ◽  
Thermal Conduction ◽  
Calibration Procedure ◽  
Classical Solutions ◽  
Refined Model ◽  
Conduction Model ◽  
Content Type ◽  
Integral Forms ◽  
Cracked Structures

Purpose This paper aims to review the existing bond-based peridynamic (PD) and state-based PD heat conduction models, and further propose a refined bond-based PD thermal conduction model by using the PD differential operator. Design/methodology/approach The general refined bond-based PD is established by replacing the local spatial derivatives in the classical heat conduction equations with their corresponding nonlocal integral forms obtained by the PD differential operator. This modeling approach is representative of the state-based PD models, whereas the resulting governing equations appear as the bond-based PD models. Findings The refined model can be reduced to the existing bond-based PD heat conduction models by specifying particular influence functions. Also, the refined model does not require any calibration procedure unlike the bond-based PD. A systematic explicit dynamic solver is introduced to validate 1 D, 2 D and 3 D heat conduction in domains with and without a crack subjected to a combination of Dirichlet, Neumann and convection boundary conditions. All of the PD predictions are in excellent agreement with the classical solutions and demonstrate the nonlocal feature and advantage of PD in dealing with heat conduction in discontinuous domains. Originality/value The existing PD heat conduction models are reviewed. A refined bond-based PD thermal conduction model by using PD differential operator is proposed and 3 D thermal conduction in intact or cracked structures is simulated.

Monte Carlo Study of Phonon Heat Conduction in Silicon Thin Films Including Contributions of Optical Phonons

2010 ◽  
Vol 132 (5) ◽  
Author(s):  
Arpit Mittal ◽  
Sandip Mazumder
Keyword(s):  
Thin Films ◽  
Thermal Conductivity ◽  
Monte Carlo ◽  
Heat Conduction ◽  
Phonon Scattering ◽  
Computational Domain ◽  
Optical Phonons ◽  
Phonon Modes ◽  
Silicon Thin Film ◽  
Silicon Thin Films

Abstract The Monte Carlo method has found prolific use in the solution of the Boltzmann transport equation for phonons for the prediction of nonequilibrium heat conduction in crystalline thin films. This paper contributes to the state-of-the-art by performing a systematic study of the role of the various phonon modes on thermal conductivity predictions, in particular, optical phonons. A procedure to calculate three-phonon scattering time-scales with the inclusion of optical phonons is described and implemented. The roles of various phonon modes are assessed. It is found that transverse acoustic (TA) phonons are the primary carriers of energy at low temperatures. At high temperatures (T&gt;200 K), longitudinal acoustic (LA) phonons carry more energy than TA phonons. When optical phonons are included, there is a significant change in the amount of energy carried by various phonons modes, especially at room temperature, where optical modes are found to carry about 25% of the energy at steady state in silicon thin films. Most importantly, it is found that inclusion of optical phonons results in better match with experimental observations for silicon thin-film thermal conductivity. The inclusion of optical phonons is found to decrease the thermal conductivity at intermediate temperatures (50–200 K) and to increase it at high temperature (&gt;200 K), especially when the film is thin. The effect of number of stochastic samples, the dimensionality of the computational domain (two-dimensional versus three-dimensional), and the lateral (in-plane) dimension of the film on the statistical accuracy and computational efficiency is systematically studied and elucidated for all temperatures.

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