Measurement of Thermoelectric Properties of Single Semiconductor Nanowires

We have measured the thermopower and the thermal conductivity of individual silicon and indium arsenide nanowires (NWs). In this study, we evaluate a self-heating method to determine the thermal conductivity λ. Experimental validation of this method was performed on highly n-doped Si NWs with diameters ranging from 20 nm to 80 nm. The Si NWs exhibited electrical resistivity of ρ=(8±4)mΩcm\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\rho = (8\pm4)\, \hbox{m}\Upomega\,\hbox{cm}$$\end{document} at room temperature and Seebeck coefficient of −(250 ± 100) μV/K. The thermal conductivity of Si NWs measured using the proposed method is very similar to previously reported values; e.g., for Si NWs with 50 nm diameter, λ = 23 W/(m K) was obtained. Using the same method, we investigated InAs NWs with diameter of 100 nm and resistivities of ρ=(25±5)mΩcm\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\rho = (25\pm5)\, \hbox{m}\Upomega\,\hbox{cm}$$\end{document} at room temperature. Thermal conductivity of λ = 1.8 W/(m K) was obtained, which is about 20 to 30 times smaller than in bulk InAs. We analyzed the accuracy of the self-heating method by means of analytical and numerical solution of the one-dimensional (1-D) heat diffusion equation taking various loss channels into account. For our NWs suspended from the substrate with low-impedance contacts the relative error can be estimated to be ≤25%.