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Thermal excitation of the low dimensional silicon film is introduced and an analytical approach is adopted for the solution of the transport equation. In the analysis, the phonon radiative transport equation is converted into an integral form of the Fredholm equation of the second kind. The analytical approach is extended to include the formulation of thermal stresses for the following cases: (i) stress-free at the edges and (ii) one edge is constrained to have maximum stress while the other edge is set to be stress-free. The analytical and numerical results are evaluated for comparisons. The findings demonstrate that both results are in good agreement. The dimensionless temperature rise at the film mid-thickness becomes sharp for small thickness film. The peak value of thermal stress at the film mid-thickness becomes larger as the film thickness is reduced further. Stress waves generated initially are compressive at the film mid-thickness and they become tensile at both ends of the stress-free film, which becomes more apparent as time increases. Two consecutive compressive and tensile stresses are generated at the mid-thickness of the film as the stress boundary condition is changed to the maximum stress at one edge of the film. [ABSTRACT FROM AUTHOR]

An analytical approach for the solution of the equation for phonon transport is presented for the combination thin films system. The transient phonon radiative transport model is considered and the combination of the silicon–diamond–silicon films is accommodated in the analysis. The multi-film system is thermally disturbed from the edges through introducing temperature difference across the combined films. Equivalent equilibrium temperature is considered quantifying the distribution of the phonon intensity in the films. Equivalent equilibrium temperature obtained from the analytical approach is compared with that predicted from the numerical solution. It is found that numerical predictions of equivalent equilibrium temperature agree well with those obtained from the analytical approach. The boundary scattering of phonons at the film edges causes equivalent equilibrium temperature jump at film edges, which becomes apparent in the early heating periods. Phonon scattering in the combined films causes sharp decay of temperature in the films, which is more pronounced in the silicon film than that of the diamond. [ABSTRACT FROM AUTHOR]

André Portela^SouzaCross-plane energy transport in aluminum and silicon films pair with presence of minute vacuum gap in between them is investigated. Laser short-pulse heating is introduced in the aluminum film and energy transfer in the films pair is formulated using the Boltzmann equation. Energy exchange between the electron and lattice subsystems is expressed in terms of the electron-phonon coupling. The vacuum gap size is considered to be less than the mean-free path silicon and the Casimir limit is applied to incorporate the thermal radiation contribution to the overall energy transport across the vacuum gap. It is found that ballistic phonon contribution to energy transfer across the vacuum gap is significant and the contribution of the thermal radiation, due to Casimir limit, to energy transfer is small. The vacuum gap size has significant effect on the energy transfer from aluminum film to the silicon film; in which case, increasing vacuum gap size enhances temperature difference across the interface of the vacuum gap. [ABSTRACT FROM AUTHOR]

Surface finishing of parts plays a critical role in engineering applications. Although the efforts towards improving surface finish have been made over the past decades, the recent developments in science and technology accelerate the progresses made towards superior surface characteristics. Tailoring the physical and chemical characteristics of the surfaces enable to extend the surface engineering studies in many new fields including medical, biological, environmental engineering, and architecture. The current interest in self-cleaning of surfaces for energy applications, such as solar thermal and solar photovoltaic energy harvesting, makes the surface finish as one of the hot topics of the research. In the present study, laser texturing of silicon surface is presented in line with the self-cleaning characteristics. It is found that laser texturing gives rise to hydrophobicity characteristics at the surface because of: i) micro/nano size pillars, and ii) nitride phase formed at the surface. [ABSTRACT FROM AUTHOR]

Energy transport across a pair of thin silicon films with the vacuum gap at the films interface is studied. The Boltzmann transport equation is incorporated in the analysis and the solution for the transient frequency-dependent phonon distribution across the films pair is presented. To assess the phonon characteristics, equivalent equilibrium temperature is introduced, which resembles the average energy of all phonons around a local point when they redistribute adiabatically to an equilibrium state. Because the gap size is comparable to the mean free path of silicon, a near-field radiation heat transfer is incorporated across the film edges at the interface. The frequency cutoff method is used at the interface of the films and the phonons jump across the gap resembling the ballistic phonon contribution to the energy transport is accommodated. The thermal conductivity data predicted are validated with the data obtained from the previous study. The effect of near-field radiation heat transfer on temperature increase at the edges of the film, across the gap interface, is not considerable as compared to that corresponding to phonons transmitted across the gap. Increasing the first film thickness increases temperature difference across the gap, which is more pronounced for large gap sizes. [ABSTRACT FROM AUTHOR]

Phonon transport in paired aluminum and silicon thin films is considered under laser short-pulse irradiation at the aluminum film surface. The Boltzmann equation is incorporated to formulate energy transport in the films. To include a volumetric source resembling laser irradiation in the aluminum film, the Boltzmann equation is modified. Thermal boundary resistance is located at the interface of the film pair. An equivalent equilibrium temperature is introduced to assess the thermal resistance of the film during the laser heating process. The phonon temperature obtained from solution of the Boltzmann equation is compared with the findings of the two-temperature model. It is found that phonon temperature obtained from the solution of the Boltzmann equation is lower than that corresponding to the two-temperature model, which is particularly true in the surface region of the aluminum film. Phonon temperature increases gradually while, early on, the electron temperature rises and decays sharply in the surface region of the aluminum film. [ABSTRACT FROM AUTHOR]

In this article, we consider phonon transport in thin silicon film and examine the influence of temporal oscillation of the temperature heat source on the phonon transport. We solve the frequency-dependent transient two-dimensional Boltzmann equation numerically to observe the quasi-ballistic effects of the phonons on the film effective thermal conductivity. Temperature oscillation at different periods is incorporated at the bottom face of the film as a heat source. The size of the temperature source is varied by introducing the spatial Gaussian distribution along this face. In order to assess the phonon distribution in the film, we introduce the equivalent equilibrium temperature. We determine the effective thermal conductivity of the film and analyze its variation due to the different periods of the temperature oscillation and the Gaussian parameters. It is found that reducing the period of the temperature oscillation lowers the effective thermal conductivity of the film, which is more pronounced for low Gaussian parameters. In this case, the quasi-ballistic behavior of phonons contributes adversely to the effective thermal conductivity of the film. [ABSTRACT FROM PUBLISHER]

Thermal transfer inside thin films with quantum-dot is considered. The Boltzmann equation is used to model the energy transport within the film when the quantum dot is thermally disturbed. Equivalent equilibrium temperature is introduced to evaluate the phonon intensity distribution inside the films. Time exponentially increasing temperature is incorporated inside the quantum dot to resemble the thermal disturbance inside the films. The wave dependent equation of phonon energy distribution is accommodated for the formulation of thermal transfer in the silicon and diamond thin films. A numerical code developed is validated through comparison of the thermal conductivity predicted and that obtained from the previous work. The findings show that film thermal conductivity data predicted is in good agreement with those reported in the previous study. Phonon intensity and temperature becomes high in the film around the quantum. Long wavelength phonons enhance phonon intensity distribution in the near region of the film edges; however, boundary scattering causes temperature jump in this region. • Phonon intensity remains high in close region of aluminum dot because of short wavelength phonons. • Large wavelengths phonon emitted increases phonon intensity in near region of film edges. • Phonon intensity almost follows temporal variation of temperature at aluminum dot edge. • Equivalent equilibrium temperature remains slightly higher for diamond thin film than that of silicon thin film. [ABSTRACT FROM AUTHOR]

The thermal conductivity of low dimensional structures remains critical for various applications. These structures can be formed from various thin films. and proper assessment of effective thermal conductivity becomes vital for the stable operation of such structures. Effective thermal conductivity of low dimension structure composing of silicon‑aluminum films is examined incorporating the thermal resistances generated in the structure. Frequency-depended phonon transfer in the structure is considered, and equivalent equilibrium temperature is adopted representing the phonon intensity. Thermal boundary resistance, resistance due to phonon scattering, and interfacial resistance are incorporated to evaluate the overall thermal resistance in the structure. The effective thermal conductivity predicted for the silicon film is compared to that of the results of the early formulation. The findings show that thermal conductivity predictions for the silicon film are in agreement with that presented in the early formulation. The slight differences in both results are because of the contribution of the ballistic phonons to thermal resistance. In addition, enlarging the silicon film thickness in the structure increases the thermal conductivity. [ABSTRACT FROM AUTHOR]