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In this work, the impact of roughness and amorphization on the effective thermal conductivity of silicon nanofilms and nanowires is studied with atomistic simulations. The discrepancy between simulations and experimental measurements shows that it is necessary to consider realistic roughness and amorphization to reach an agreement. We show that subnanometric roughness and specific correlation length can reduce thermal transport by a factor of two in both nanofilms and nanowires; in addition, this reduction is even more pronounced than the one related to the existence of native oxides or amorphous phases on nanostructure edges. Furthermore, an interfacial thermal resistance parallel to the heat flux is observed. This thermal resistance is increasing upon the increase of the amorphous shell thickness, reaching a maximum value for thickness of 6 nm. Our findings could improve the strategy to elaborate nanomaterials with enhanced thermoelectric efficiency by tuning thermal conductivity through the engineering of surfaces. [ABSTRACT FROM AUTHOR]

This study deals with phonon heat transport in silicon nanowires. A review of various methods that can be used to assess thermal conductance of such nanodevices is pre-sented. Here, a specific attention is paid to the case of the Landauer Formalism, which can describe extremely thin wires conductance. In order to use this technique, the calcu-lation of propagating modes in a silicon nanowire is necessary. Among the several exist-ing models allowing such calculation, the elastic wave theory has been used to obtain the normal mode number. Besides, in this study, the transmission and reflection of phonon at the interface between two nanostructures are discussed. Using the diffuse mismatch model (DMM), the global transmissivity of the system made of a nanowire suspended between two thermal reservoirs is addressed. Then, the calculations of normal modes' numbers and thermal conductances of several silicon nanowires, with various diameters set between bulk thermal reservoirs, are presented and compared to other models and available experiments. [ABSTRACT FROM AUTHOR]

In this work, we investigated the tensile and compression forces effect on the thermal conductivity of silicon. We used the equilibrium molecular dynamics approach for the evaluation of thermal conductivity considering different interatomic potentials. More specifically, we tested Stillinger-Weber, Tersoff, Environment-Dependent Interatomic Potential, and Modified Embedded Atom Method potentials for the description of silicon atom motion under different strain and temperature conditions. It was shown that the Tersoff potential gives a correct trend of the thermal conductivity with the hydrostatic strain, while other potentials fail, especially when the compression strain is applied. Additionally, we extracted phonon density of states and dispersion curves from molecular dynamics simulations. These data were used for direct calculations of the thermal conductivity considering the kinetic theory approach. Comparison of molecular dynamics and kinetic theory simulations results as a function of strain and temperature allowed us to investigate the different factors affecting the thermal conductivity of the strained silicon. [ABSTRACT FROM AUTHOR]

The thermal conductivity of a series of structural, diameter, and core/shell modulated silicon nanowires is computed by molecular dynamics simulations using the nonequilibrium method. The purpose of this study is to appraise the impact of surface roughness, amorphous parts integration, and diameter modulation on the thermal conductivity reduction. The addition of both amorphous regions and nanoconstrictions allows us to reach a thermal conductivity close to that of the amorphous pristine nanowires, while preserving a certain degree of crystallinity. This could result in interesting properties for thermoelectric applications. [ABSTRACT FROM AUTHOR]