Atomistic calculation of the thermoelectric properties of Si nanowires

TL;DR

This study uses atomistic models to calculate the thermoelectric properties of silicon nanowires across a wide temperature range, considering detailed electron-phonon interactions and surface passivation effects.

Contribution

It introduces a comprehensive atomistic approach to evaluate thermoelectric properties of Si nanowires, including electron-phonon interactions and surface passivation effects.

Findings

Electron mobility is 195 cm^2/(Vs) at room temperature and increases with temperature.

A figure-of-merit ZT of 0.38 is achieved at room temperature for n-type doping.

The model accurately captures temperature-dependent transport characteristics.

Abstract

The thermoelectric properties of 1.6 nm-thick Si square nanowires with [100] crystalline orientation are calculated over a wide temperature range from 0 K to 1000 K, taking into account atomistic electron-phonon interaction. In our model, the [010] and [001] facets are passivated by hydrogen and there are Si-Si dimers on the nanowire surface. The electronic structure was calculated by using the sp^3 spin-orbit-coupled atomistic second-nearest-neighbor tight-binding model. The phonon dispersion was calculated from a valence force field model of the Brenner type. A scheme for calculating electron-phonon matrix elements from a second-nearest neighbor tight-binding model is presented. Based on Fermi's golden rule, the electron-phonon transition rate was obtained by combining the electron and phonon eigenstates. Both elastic and inelastic scattering processes are taken into consideration. The temperature dependence of transport characteristics was calculated by using a solution of linearized Boltzmann transport equation obtained by means of the iterative Orthomin method. At room temperature, the electron mobility is 195 cm^2/(Vs) and increases with temperature, while a figure-of-mertit ZT=0.38 is reached for n-type doping with a concentration of n=10^19 cm^-3.