Thermoelectric Properties of Scaled Silicon Nanowires Using the sp3d5s*-SO Atomistic Tight-Binding Model and Boltzmann Transport

Abstract

As a result of suppressed phonon conduction, large improvements of the thermoelectric figure of merit, ZT, have been recently reported for nanostructures compared to the raw materials' ZT values. It has also been suggested that low dimensionality can improve a device's power factor as well, offering a further enhancement. In this work the atomistic sp3d5s*-spin-orbit-coupled tight-binding model is used to calculate the electronic structure of silicon nanowires (NWs). The linearized Boltzmann transport theory is applied, including all relevant scattering mechanisms, to calculate the electrical conductivity, the Seebeck coefficient, and the thermoelectric power factor. We examine n-type nanowires of diameters of 3nm and 12nm, in [100], [110], and [111] transport orientations at different carrier concentrations. Using experimental values for the lattice thermal conductivity in nanowires, the expected ZT value is computed. We find that at room temperature, although scaling the diameter below 7nm can be beneficial to the power factor due to banstructure changes alone, at those dimensions enhanced phonon and surface roughness scattering degrades the conductivity and reduces the power factor.

19 pages, 5 figures; Journal of electronic Materials, 2011

References in corpus (5)

• Mobility in Semiconducting Graphene Nanoribbons: Phonon, Impurity, and Edge Roughness Scattering
• Bandstructure Effects in Silicon Nanowire Electron Transport
• Bandstructure Effects in Silicon Nanowire Hole Transport
• On the Bandstructure Velocity and Ballistic Current of Ultra Narrow Silicon Nanowire Transistors as a Function of Cross Section Size, Orientation and Bias
• Analysis of Thermoelectric Properties of Scaled Silicon Nanowires Using an Atomistic Tight-Binding Model