Silicon Thin-Film Lattice Dynamics and Thermal Transport Properties

2012 ◽  
Author(s):  
Bruce L. Davis ◽  
Mehmet Su ◽  
Ihab El-Kady ◽  
Mahmoud I. Hussein
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Thermal Conductivity ◽  
Transport Properties ◽  
Lattice Dynamics ◽  
Dielectric Materials ◽  
Phonon Transport ◽  
Solid State Physics ◽  
Silicon Thin Film ◽  
Silicon Thin Films

Thin films composed of dielectric materials are attracting growing interest in the solid state physics and nanoscale heat transfer communities. This is primarily due to their unique thermal and electronic properties and their extensive use as components in optoelectronic, and potentially in thermoelectric, devices. In this paper, an elaborate study is presented on silicon thin films ranging from a few nanometers in thickness to very thick bulk-like thicknesses. Full lattice dynamics calculations are performed incorporating the entire film cross section and the relaxation of the free surfaces. The phonon properties emerging from these calculations are then incorporated into Holland-Callaway models to predict the thermal conductivity and other phonon transport properties. A rigorous curve fitting process to a limited set of available experimental data is carried out to obtain the scattering lifetimes. Our results demonstrate the importance of proper consideration of the full thin-film dispersion description and provide insights into the relationship between thermal conductivity, film thickness and temperature.

Effects of Confinement and Surface Reconstruction on the Lattice Dynamics and Thermal Transport Properties of Thin Films

2007 ◽  
Author(s):  
Joseph E. Turney ◽  
A. J. H. McGaughey ◽  
C. H. Amon
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Lattice Dynamics ◽  
Phonon Dispersion ◽  
Phonon Transport ◽  
Phonon Dispersion Curves ◽  
Lennard Jones ◽  
Silicon Thin Films ◽  
Plane Direction ◽  
Bulk System

Phonon transport in argon and silicon thin films is examined using harmonic lattice dynamics theory and the Lennard-Jones and Stillinger-Weber potentials. Film thicknesses ranging from 0.8 to 33.5 nm for argon and 0.4 to 8.6 nm for silicon are examined at a temperature of 0 K. Both reconstructed films and films built using the bulk unit cell are considered. Phonon dispersion curves for the in-plane direction and the density of states are computed from lattice dynamics and compared to predictions for a bulk system. The results from the lattice dynamics calculations are used to predict the thermal conductivities of the bulk and thin film structures.

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>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 (>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.

Soluble polycyclosilane–polysiloxane hybrid material and silicon thin film with optical properties at 193 nm and etch selectivity

2015 ◽  
Vol 3 (2) ◽  
pp. 239-242 ◽  
Author(s):  
Sung Jin Park ◽  
Hyeon Mo Cho ◽  
Myong Euy Lee ◽  
Miyoung Kim ◽  
Kwenwoo Han ◽  
...  
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Optical Properties ◽  
Hybrid Materials ◽  
Hybrid Material ◽  
Silicon Thin Film ◽  
New Class ◽  
Silicon Thin Films ◽  
193 Nm

Silicon thin films that fulfil the needs of current semiconductor lithography were prepared from a new class of polycyclosilane–polysiloxane hybrid materials.

Monte Carlo Study of Phonon Heat Conduction in Silicon Thin Films: Role of Optical Phonons

2009 ◽  
Author(s):  
Arpit Mittal ◽  
Sandip Mazumder
Keyword(s):  
Thin Films ◽  
Thermal Conductivity ◽  
Monte Carlo ◽  
Heat Conduction ◽  
Optical Phonons ◽  
Boltzmann Transport ◽  
Phonon Modes ◽  
Silicon Thin Film ◽  
Silicon Thin Films

The Monte Carlo (MC) method has found prolific use in the solution of the Boltzmann Transport Equation (BTE) for phonons for the prediction of non-equilibrium 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 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 > 200K), 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. At room temperature, optical modes are found to carry about 25% of the energy at steady state in Silicon thin films. Most importantly, inclusion of optical phonons results in better match with experimental observations for Silicon thin-film thermal conductivity.

Phonon transport characteristics across silicon thin film pair: Presence of a gap between the films

2015 ◽  
Vol 40 (3) ◽  
Author(s):  
Haider Ali ◽  
Bekir S. Yilbas
Keyword(s):  
Thin Film ◽  
Experimental Data ◽  
Thermal Conductivity ◽  
Temperature Difference ◽  
Radiation Heat Transfer ◽  
Phonon Transport ◽  
Radiative Energy ◽  
Gap Size ◽  
Boltzmann Transport ◽  
Silicon Thin Film

AbstractPhonon transport across silicon thin film pair with minute gap (Casimir limit) between the films is studied. Phonon transport characteristics across the gap are examined for various gap sizes, and the transient solution of the frequency-dependent Boltzmann transport equation is presented according to relevant boundary conditions incorporating the gap between the film pair. Since the gap size is minute (Casimir limit), the radiative energy transport between the edges of the film pair is incorporated. In addition, phonon transmission and reflection is introduced at the gap edges, thus satisfying energy conservation. The thermal conductivity predicted is validated through experimental data reported in the open literature. Predicted thermal conductivity data agree well with the experimental data reported in the open literature. Increasing gap size alters the phonon transport characteristics across the film pair. Increasing gap size enhances temperature difference between the edges of the gap; in which case, the effect of phonon transmittance is more significant on the temperature difference than that corresponding to the radiation heat transfer due to Casimir limit.

Porous silicon thin film gas sensor

2001 ◽  
Vol 664 ◽  
Author(s):  
I. Ferreira ◽  
E. Fortunato ◽  
R. Martins
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Porous Silicon ◽  
Chemical Vapour ◽  
Preparation Condition ◽  
Current Response ◽  
Silicon Thin Film ◽  
Silicon Thin Films ◽  
Nano Crystalline ◽  
Gas Detector

ABSTRACTThe performances of amorphous and nano-crystalline porous silicon thin films as gas detector are pioneer reported in this work. The films were produced by the hot wire chemical vapour deposition (HW-CVD). These films present a porous like-structure, which is due to the uncompensated bonds and oxidise easily in the presence of air. This behaviour is a problem when the films are used for solar cells or thin film transistors. For as gas detectors, the oxidation is a benefit, since the CO, H2 or O2 molecules replace the OH adsorbed group. In the present study we observe the behaviour of amorphous and nano-crystalline porous silicon thin films under the presence of ethanol, at room temperature. The data obtained reveal a change in the current values recorded by more than three orders of magnitude, depending on the film preparation condition. This current behaviouris due to the adsorption of the OH chemical group by the Si uncompensated bonds as can be observed in the infrared spectra. Besides that, the current response and its recover time are done in few seconds.

The Structure of Silicon Thin Films Grown on Sapphire by MBE

1987 ◽  
Vol 107 ◽  
Author(s):  
M. E. Twigg ◽  
J. G. Pellegrino ◽  
E. D. Richmond
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Vapor Deposition ◽  
Molecular Beam ◽  
Film Growth ◽  
Chemical Vapor ◽  
Thin Film Growth ◽  
Silicon Thin Film ◽  
Silicon Thin Films ◽  
Transmission Electron

AbstractFrom a series of imaging experiments performed in the transmission electron microscope (TEM), it is apparent that for silicon grown on sapphire (SOS) by molecular beam epitaxy (MBE), silicon thin film growth on the (1012) sapphire plane resembles that observed for analogous films grown by chemical vapor deposition (CVD). At 900°C very thin (150A) silicon films grow as islands with either the (001) or (110) planes parallel to the (1012) plane; it is also found that most of the silicon grows as (001) rather than (110) islands, as is true for CVD-grown SOS. The orientation, however, of (110) islands occuring in this MBE-grown SOS sample differs from that of (110) islands occuring in CVD-grown SOS. By following this initial 150A of growth with 2500A of silicon deposited at. 750°C, a continuous (001) film was grown in which microtwins appear to be the predominant defect. The MBE-grown SOS also resembles that grown by CVD in that the microtwin densities associated with the “majority” and “minority” twinning systems are influenced by the orientation of the sapphire substrate.

Silicon Thin Film Thermal Conductivity in Ballistic and Diffusive Regimes Predicted by Molecular Dynamics

2005 ◽  
Author(s):  
Carlos J. Gomes ◽  
Marcela Madrid ◽  
Javier V. Goicochea ◽  
Cristina H. Amon
Keyword(s):  
Thin Films ◽  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Film Thickness ◽  
Interatomic Potential ◽  
Mean Free Path ◽  
Technical Conference ◽  
Silicon Thin Film ◽  
Silicon Thin Films ◽  
Out Of Plane

The thermal conductivity of silicon thin films is predicted in the directions parallel and perpendicular to the film surfaces (in-plane and out-of-plane, respectively) using equilibrium molecular dynamics, the Green-Kubo relationship and the Stillinger-Weber interatomic potential. Film thicknesses range from 2 to 220 nm and temperatures from 300 to 1000 K. In this range of temperatures, the relation between the phonon mean free path (Λ) and the film thickness (ds) spans from the ballistic regime (≫ ds) to the diffusive, bulk-like regime (≪ ds). We show that equilibrium molecular dynamics and the Green-Kubo relationship can be applied to the study of the thermal conductivity of thin films in the ballistic, transitional and diffusive regimes. When the film is thin enough, the thermal conductivity becomes orthotropic and decreases with decreasing film thickness as a consequence of the scattering of phonons with the film boundaries. The in-plane thermal conductivity follows the trend observed experimentally at 300 K. In the ballistic limit, in accordance with the kinetic theory, the predicted out-of-plane thermal conductivity varies linearly with the film thickness and is temperature-independent for temperatures near or above Debye’s temperature.   This paper was also originally published as part of the Proceedings of the ASME 2005 Pacific Rim Technical Conference and Exhibition on Integration and Packaging of MEMS, NEMS, and Electronic Systems.

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