Tuning thermal conductivity of nanoporous crystalline silicon by surface passivation: A molecular dynamics study

Effect of hydrogen passivation on thermal conductivity of nanoporous crystalline silicon was investigated using equilibrium molecular dynamics (MD) simulations from 500 to 1000 K. The porosity varied from 8% to 38% while the pore diameter ranged from 1.74 to 2.93 nm. Hydrogen passivation of the pore surface was found to reduce thermal conductivity by about 20% at 500 K due to enhanced phonon scattering by the passivated atoms at the nanopore surface. The effect of passivation diminished with increasing temperature. In fact, the phonon density of states at high temperatures was similar for both passivated and unpassivated silicon atoms. Finally, the thermal conductivity k was found to be linearly proportional to (1–1.5fv)/(Ai/4) where fv is the porosity and Ai is the pore interfacial area concentration. This scaling law was previously established for un-passivated silicon using non-equilibrium MD simulations.

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Thermal conductivity of regularly spaced amorphous/crystalline silicon superlattices. A molecular dynamics study

MRS Proceedings ◽

10.1557/opl.2013.671 ◽

2013 ◽

Vol 1543 ◽

pp. 71-79 ◽

Cited By ~ 3

Author(s):

Konstantinos TERMENTZIDIS ◽

Arthur FRANCE-LANORD ◽

Etienne BLANDRE ◽

Tristan ALBARET ◽

Samy MERABIA ◽

...

Keyword(s):

Heat Transfer ◽

Thermal Conductivity ◽

Molecular Dynamics ◽

Thermal Transport ◽

Crystalline Silicon ◽

Vibrational Modes

ABSTRACTThe thermal transport in amorphous/crystalline silicon superlattices with means of molecular dynamics is presented in the current study. The procedure used to build such structures is discussed. Then, thermal conductivity of various samples is studied as a function of the periodicity of regular superlattices and of the applied temperature. Preliminarily results show that for regular amorphous/crystalline superlattices, the amorphous regions control the heat transfer within the structures. Secondly, in the studied cases thermal conductivity weakly varies with the temperature. This, points out the presence of a majority of non-propagating vibrational modes in such systems.

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Thermal Conductivity of Crystalline Nanoporous Silicon Using Molecular Dynamics Simulations

Volume 10: Heat and Mass Transport Processes, Parts A and B ◽

10.1115/imece2011-64785 ◽

2011 ◽

Author(s):

Jin Fang ◽

Laurent Pilon

Keyword(s):

Thermal Conductivity ◽

Molecular Dynamics ◽

Effective Thermal Conductivity ◽

Crystalline Silicon ◽

Interfacial Area ◽

Md Simulations ◽

Nanoporous Silicon ◽

Vacancy Defects ◽

Interfacial Area Concentration ◽

Dynamics Simulations

This study establishes that the effective thermal conductivity keff of crystalline nanoporous silicon is strongly affected not only by the porosity fv and the system’s length Lz but also by the pore interfacial area concentration Ai. The thermal conductivity of crystalline nanoporous silicon was predicted using non-equilibrium molecular dynamics (NEMD) simulations. The Stillinger-Weber potential for silicon was used to simulate the interatomic interactions. Spherical pores organized in a simple cubic lattice were introduced in a crystalline silicon matrix by removing atoms within selected regions of the simulation cell. Effects of the (i) system length ranging from 13 to 130 nm, (ii) pore diameter varying between 1.74 and 5.86 nm, and (iii) porosity ranging from 8% to 38%, on thermal conductivity were investigated. A physics-based model was also developed by combining kinetic theory and the coherent potential approximation. The effective thermal conductivity was proportional to (1–1.5fv) and inversely proportional to the sum (Ai/4+1/Lz). This model was in excellent agreement with the thermal conductivity of nanoporous silicon predicted by MD simulations for spherical pores (present study) as well as for cylindrical pores and vacancy defects reported in the literature. These results will be useful in designing nanostructured materials with desired thermal conductivity by tuning their morphology.

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