Seebeck coefficient of nanowires interconnected into large area networks

We measured the macroscopic Seebeck coefficient of silicon nanowires (SiNWs), organized in a highly interconnected networks on large areas (order of mm(2)). The fabricated networks are very reliable with respect to random nanowire failure and are electrically and thermally equivalent to many SiNWs placed in parallel between the electrical contacts. The equivalent SiNWs have a macroscopic length of the order of millimeters and are very narrow (width smaller than 100 nm) so that they can be used to exploit thermoelectric properties at nanoscale for macroscopic electrical power generation and/or cooling. The measurement of the Seebeck coefficient S, facilitated by the macroscopic dimensions of the network, gives an insight into two questions, nanowire effective doping and carrier mobility, which are widely discussed in the literature. We found that the measured value of S is compatible with an effective doping that is higher than that of the original wafer. This higher doping is consistent with the value estimated from the measured electrical conductivity of the SiNWs with the assumption that the electron mobility inside the nanowire is equal to that of bulk silicon.