Simultaneous measurements of Seebeck coefficient and thermal conductivity across superlattice

A method is developed to simultaneously measure the Seebeck coefficient and thermal conductivity in the cross-plane direction of thin films and applied to an n-type Si/Ge quantum-dot superlattice. In this method, an Au/Cr pattern serves as both a heater and a thermometer, and a microprobe is prepared between the heater and the thin film to extract the Seebeck voltage. Using a differential measurement between the thin films with different thickness, the temperature and voltage drops across the thin film are determined to deduce its cross-plane thermal conductivity and Seebeck coefficient. At room temperature, the cross-plane Seebeck coefficient and thermal conductivity are 312 μV/K and 2.92 W/mK, respectively, for the n-type Si(75 Å)/Ge(15 Å) quantum-dot superlattice doped to 8.7×1019 cm−3.