KFM evaluation of seebeck coefficient in thin SOI layers

摘要

Although the introduction of nanostructures into thermoelectric materials is one of key technology for enhancement in thermoelectric conversion efficiency, a technique for characterizing the nanometer-scale materials is required. With the aim of evaluating Seebeck coefficient of nanostructured thermoelectric materials, we propose a new technique by Kelvin- probe force microscopy (KFM) which gives us local surface potential corresponding to the Fermi energy difference of a sample relative to the cantilever. Hence, thermoelectromotive force and temperature difference are obtained from the surface potentials and temperatures at the high- and low-temperature regions on the sample, which leads to evaluation of Seebeck coefficient. First of all, the Seebeck coefficients of bulk Si wafers and Si-on-insulator (SOI) layers were measured. At present, the Seebeck coefficient is evaluated to be −2.8mV/K for a SOI layer, which is larger than the value obtained by a conventional method.