The Effect of Nanoparticles on the Thermal Conductivity of Crystalline Thin Films at Low Temperatures

2007 ◽  
Author(s):  
Kamal M. Katika ◽  
Laurent Pilon
Keyword(s):  
Thin Films ◽  
Thermal Conductivity ◽  
Radiative Transfer ◽  
Film Thickness ◽  
Volume Fraction ◽  
Phonon Transport ◽  
Solid Matrix ◽  
Discrete Ordinates ◽  
Nanoparticle Radius ◽  
Nanocomposite Thin Films

This study is concerned with the prediction of the effective thermal conductivity of nanocomposite thin films consisting of nanoparticles randomly distributed in a solid matrix. Crystalline sodium chloride with embedded monodisperse silver nanoparticles is investigated as a case study for thin films where phonons are the main heat carriers. To the best of our knowledge, the equation for phonon radiative transfer is solved for the first time with an exact scattering transport cross-section of the nanoparticles as a function of frequency which was obtained from the literature. The one-dimensional equation for phonon radiative transfer based on the isotropic scaling approximation is solved on a spectral basis using the discrete ordinates method to predict the temperature profile and the heat flux across the nanocomposite thin films. The thermal conductivity is retrieved at temperatures where the effects of Umklapp and Normal processes can be neglected and scattering by the particles on phonon transport dominates. The method of solution and closure laws were validated with experimental data of thermal conductivity for bulk samples at 2.53, 5.94, and 10.56 K. The effects of the film thickness (1 μm to 2.5 cm), nanoparticle diameter (5 nm to 100 nm) and volume fraction (0.0001 to 0.2) on the thermal conductivity of the nanocomposite thin film are investigated. The results indicate that the thermal conductivity decreases with decreasing particle radius as well as with increasing particle concentration. Finally, a dimensionless analysis revealed a power law relationship between the dimensionless thermal conductivity and a dimensionless length of the order of the acoustic thickness of the medium. These results can be used to design nanocomposite thin films for various low temperature thermal applications by choosing optimal nanoparticle radius and volume fraction, and film thickness.

Microscale Heat Conduction in Dielectric Thin Films

1993 ◽  
Vol 115 (1) ◽  
pp. 7-16 ◽  
Author(s):  
A. Majumdar
Keyword(s):  
Thin Films ◽  
Thermal Conductivity ◽  
Heat Flux ◽  
Heat Conduction ◽  
Radiative Transfer ◽  
Film Thickness ◽  
Heat Transport ◽  
Phonon Scattering ◽  
Fourier Law ◽  
Dielectric Thin Films

Heat conduction in dielectric thin films is a critical issue in the design of electronic devices and packages. Depending on the material properties, there exists a range of film thickness where the Fourier law, used for macroscale heat conduction, cannot be applied. This paper shows that in this microscale regime, heat transport by lattice vibrations or phonons can be analyzed as a radiative transfer problem. Based on Boltzmann transport theory, an equation of phonon radiative transfer (EPRT) is developed. In the acoustically thick limit, ξL ≫ 1, or the macroscale regime, where the film thickness is much larger than the phonon-scattering mean free path, the EPRT reduces to the Fourier law. In the acoustically thin limit, ξL ≪ 1, the EPRT yields the blackbody radiation law q = σ (T14 − T24) at temperatures below the Debye temperature, where q is the heat flux and T1 and T2 are temperatures at the film boundaries. For transient heat conduction, the EPRT suggests that a heat pulse is transported as a wave, which becomes attenuated in the film due to phonon scattering. It is also shown that the hyperbolic heat equation can be derived from the EPRT only in the acoustically thick limit. The EPRT is then used to study heat transport in diamond thin films in wide range of acoustical thicknesses spanning the thin and the thick regimes. The heat flux follows the relation q = 4σT3ΔT/(3ξL/4 + 1) as derived in the modified diffusion approximation for photon radiative transfer. The thermal conductivity, as currently predicted by kinetic theory, causes the Fourier law to overpredict the heat flux by 33 percent when ξL ≪ 1, by 133 percent when ξL = 1, and by about 10 percent when ξL increases to 10. To use the Fourier law in both ballistic and diffusive transport regimes, a simple expression for an effective thermal conductivity is developed.

Non-epitaxial, Highly Textured (001) CoPt:B2O3 Composite Films for Perpendicular Recording

2002 ◽  
Vol 721 ◽  
Author(s):  
M. L. Yan ◽  
N. Powers ◽  
D. J. Sellmyer
Keyword(s):  
Thin Films ◽  
Film Thickness ◽  
Epitaxial Growth ◽  
Thermal Processing ◽  
Composite Films ◽  
Annealing Process ◽  
Perpendicular Anisotropy ◽  
Perpendicular Recording ◽  
Nanocomposite Thin Films ◽  
Deposited Films

AbstractWe report the non-epitaxial growth of highly textured (001) CoPt:B2O3 nanocomposite thin films that are deposited directly on thermally-oxidized Si wafers. Multilayers of Co/Pt/Co/B2O3 are deposited followed by appropriate thermal processing. The as-deposited films are disordered fcc CoPt phase, and magnetically soft. After annealing, an (001) orientation of CoPt-ordered grains is developed. The texture development is dependent both on the total film thickness and the annealing process. Nearly perfect (001) texture can be obtained in films with thinner initial layer thicknesses. Strong perpendicular anisotropy is shown to be related to this (001) texture.

scholarly journals Effect of Grain Size and Film Thickness on the Thermoelectric Properties of Flexible Sb2Te3 Thin Films

2019 ◽  
Vol 2019 ◽  
pp. 1-7 ◽  
Author(s):  
Pornsiri Wanarattikan ◽  
Piya Jitthammapirom ◽  
Rachsak Sakdanuphab ◽  
Aparporn Sakulkalavek
Keyword(s):  
Thin Films ◽  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Grain Size ◽  
Film Thickness ◽  
Seebeck Coefficient ◽  
Thermoelectric Properties ◽  
Flexible Substrate ◽  
Rf Magnetron Sputtering ◽  
Mean Free Path

In this work, stoichiometric Sb2Te3 thin films with various thicknesses were deposited on a flexible substrate using RF magnetron sputtering. The grain size and thickness effects on the thermoelectric properties, such as the Seebeck coefficient (S), electrical conductivity (σ), power factor (PF), and thermal conductivity (k), were investigated. The results show that the grain size was directly related to film thickness. As the film thickness increased, the grain size also increased. The Seebeck coefficient and electrical conductivity corresponded to the grain size of the films. The mean free path of carriers increases as the grain size increases, resulting in a decrease in the Seebeck coefficient and increase in electrical conductivity. Electrical conductivity strongly affects the temperature dependence of PF which results in the highest value of 7.5 × 10−4 W/m·K2 at 250°C for film thickness thicker than 1 µm. In the thermal conductivity mechanism, film thickness affects the dominance of phonons or carriers. For film thicknesses less than 1 µm, the behaviour of the phonons is dominant, while both are dominant for film thicknesses greater than 1 µm. Control of the grain size and film thickness is thus critical for controlling the performance of Sb2Te3 thin films.

THREE-DIMENSIONAL PHONON TRANSPORT SIMULATION FOR NANO/MICROSTRUCTURED MATERIALS

2008 ◽  
Vol 07 (02n03) ◽  
pp. 103-112 ◽  
Author(s):  
A. SAKURAI ◽  
S. MARUYAMA ◽  
A. KOMIYA ◽  
K. MIYAZAKI
Keyword(s):  
Radiative Transfer ◽  
Heat Transport ◽  
Characteristic Length ◽  
Transport Phenomena ◽  
Three Dimensional ◽  
Phonon Transport ◽  
Discrete Ordinates ◽  
Complex Geometries ◽  
Transport Mechanisms ◽  
Length Scales

The Discrete Ordinates Radiation Element Method (DOREM), which is radiative transfer code, is applied for solving phonon transport of nano/microscale materials. The DOREM allows phonon simulation with multi-dimensional complex geometries. The objective of this study is to apply the DOREM to the nano/microstructured materials. It is confirmed that significant changes of the heat transport phenomena with different characteristic length scales and geometries are observed. This study also discusses further variations for understanding of heat transport mechanisms.

Optical Properties of Nanocomposite Thin-Films

2006 ◽  
Author(s):  
Anna Garahan ◽  
Laurent Pilon ◽  
Juan Yin ◽  
Indu Saxena
Keyword(s):  
Thin Films ◽  
Optical Properties ◽  
Maxwell’S Equations ◽  
Maxwell's Equations ◽  
Volume Fraction ◽  
Effective Index ◽  
Absorption Index ◽  
Index Of Refraction ◽  
Nanocomposite Thin Films ◽  
Effective Index Of Refraction

This paper aims at developing numerically validated models for predicting the through-plane effective index of refraction and absorption index of nanocomposite thin-films. First, models for the effective optical properties are derived from previously reported analysis applying the volume averaging theory (VAT) to the Maxwell's equations. The transmittance and reflectance of nanoporous thin-films are computed by solving the Maxwell's equations and the associated boundary conditions at all interfaces using finite element methods. The effective optical properties of the films are retrieved by minimizing the root mean square of the relative errors between the computed and theoretical transmittance and reflectance. Nanoporous thin-films made of SiO2 and TiO2 consisting of cylindrical nanopores and nanowires are investigated for different diameters and various porosities. Similarly, electromagnetic wave transport through dielectric medium with embedded metallic nanowires are simulated. Numerical results are compared with predictions from widely used effective property models including (1) Maxwell-Garnett Theory, (2) Bruggeman effective medium approximation, (3) parallel, (4) series, (5) Lorentz-Lorenz, and (6) VAT models. Very good agreement is found with the VAT model for both the effective index of refraction and absorption index. Finally, the effect of volume fraction on the effective complex index of refraction predicted by the VAT model is discussed. For certain values of wavelengths and volume fractions, the effective index of refraction or absorption index of the composite material can be smaller than that of both the continuous and dispersed phases. These results indicate guidelines for designing nanocomposite optical materials.

Molecular Dynamics Simulation on the Out-of Plane Thermal Conductivity of Single-Crystal Carbon Thin Films

2009 ◽  
Vol 60-61 ◽  
pp. 430-434 ◽  
Author(s):  
Xing Li Zhang ◽  
Zhao Wei Sun ◽  
Guo Qiang Wu
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Potential Energy ◽  
Film Thickness ◽  
Single Crystal ◽  
Diamond Crystal ◽  
Dynamics Simulation ◽  
Crystal Direction

In this article, we select corresponding Tersoff potential energy to build potential energy model and investigate the thermal conductivities of single-crystal carbon thin-film. The equilibrium molecular dynamics (EMD) method is used to calculate the nanometer thin film thermal conductivity of diamond crystal at crystal direction (001), and the non-equilibrium molecular dynamics (NEMD) is used to calculate the nanometer thin film thermal conductivity of diamond crystal at crystal direction (111). The results of calculations demonstrate that the nanometer thin film thermal conductivity of diamond crystal is remarkably lower than the corresponding bulk experimental data and increase with increasing the film thickness, and the nanometer thin film thermal conductivity of diamond crystal relates to film thickness linearly in the simulative range. The nanometer thin film thermal conductivity also demonstrates certain regularity with the change of temperature. This work shows that molecular dynamics, applied under the correct conditions, is a viable tool for calculating the thermal conductivity of nanometer thin films.

Size-controlled growth and antibacterial mechanism for Cu:C nanocomposite thin films

2017 ◽  
Vol 19 (1) ◽  
pp. 237-244 ◽  
Author(s):  
Amjed Javid ◽  
Manish Kumar ◽  
Seokyoung Yoon ◽  
Jung Heon Lee ◽  
Jeon Geon Han
Keyword(s):  
Thin Films ◽  
Antibacterial Activity ◽  
Volume Fraction ◽  
Size Reduction ◽  
Antibacterial Mechanism ◽  
Cu Nanoparticles ◽  
Plasma Energy ◽  
Fixed Volume ◽  
Nanocomposite Thin Films ◽  
Size Controlled

Plasma energy induced size reduction of Cu nanoparticles (at fixed volume fraction) in C matrix demonstrated effective antibacterial activity.

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.

Isothermal Physical Aging of Poly(ethyl methacrylate)/Polyhedral Oligomeric Silsequioxanes Nanocomposite Thin Films

2011 ◽  
Vol 287-290 ◽  
pp. 2234-2239 ◽  
Author(s):  
Sil Ro Jin ◽  
Jong Keun Lee
Keyword(s):  
Thin Films ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Film Thickness ◽  
Methyl Methacrylate ◽  
Relaxation Function ◽  
Physical Aging ◽  
Pmma Film ◽  
Nanocomposite Thin Films

The effects of the polyhedral oligomeric silsequioxanes (POSS) in stacked poly(methyl methacrylate) (PMMA) film samples were investigated in two different film thicknesses, ~50 and ~660 nm. The types of the POSS include methacryl-, octaisobutyl-, and octasilane-POSS. The glass transition temperature (Tg) and isothermal physical aging was depressed by the reduction of film thickness. Among POSS molecules used in this work, methacryl-POSS was the greatest effect in both Tgand relaxation enthalpy (DHRelax) due to the physical aging. The Kohlrausch-Williams-Watts (KWW) relaxation function was used to further understand the effect of POSS and film thickness on the physical aging.

Estimating Density Reduction and Phonon Localization From Optical Thermal Conductivity Measurements of Porous Silica and Aerogel Thin Films

2011 ◽  
Author(s):  
Patrick E. Hopkins ◽  
Bryan J. Kaehr ◽  
Darren Dunphy ◽  
C. Jeffrey Brinker
Keyword(s):  
Thin Films ◽  
Thermal Conductivity ◽  
Mesoporous Silica ◽  
Porous Silica ◽  
Thermal Effusivity ◽  
Solid Matrix ◽  
Silica Films ◽  
Density Reduction ◽  
The Difference ◽  
Phonon Localization

In this work, we measure the thermal conductivity of mesoporous silica and aerogel thin-films using a non-destructive optical technique: time domain thermoreflectance (TDTR). Due to the rough surfaces of the optically transparent silica-based films, we evaporate an Al film on a glass cover slide and fabricate the silica structures directly on the Al film, providing a “probe-through-the-glass” configuration for TDTR measurements. This allows the thermal conductivity of mesoporous silica and aerogel thin films to be measured with traditional TDTR analyses. As the thermoreflectance response is highly dependent on the thermal effusivity of the porous structures, we estimate the density of the films by varying the heat capacity in our analysis. This density determination assumes that the solid matrix in the silica structure has the thermal conductivity as bulk SiO2, which is valid if all the lattice vibrations are localized, consistent with the minimum thermal conductivity concept. We independently determine the density of the porous silica films with nitrogen sorption measurements of thin films using a surface acoustic wave (SAW) technique. The difference between the determined from the SAW technique and that estimated by the TDTR effusivity analysis lends insight into the relative contributions of localized and propagating modes to thermal transport.

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