Improved thermoelectric property of B-doped Si/Ge multilayered quantum dot films prepared by RF magnetron sputtering

The use of nanostructured thermoelectric materials that can effectively reduce the lattice conductivity with minimal effects on electrical properties has been recognized as the most successful approach to decoupling three key parameters (S, σ, and κ) and reaching high a dimensionless figure of merit (ZT) values. Here, five-period multilayer films consisting of 10 nm B-doped Si, 1.1 nm B, and 13 nm B-doped Ge layers in each period were prepared on Si wafer substrates using a magnetron sputtering system. Nanocrystallites of 22 nm diameter were formed by post-annealing at 800 °C in a short time. The nanostructures were confirmed by X-ray diffraction analysis, Raman spectroscopy, and transmission electron microscopy. The maximum Seebeck coefficient of Si/Ge films is significantly increased to 850 μV/K at 200 °C with their electrical resistivity decreased to 1.3 × 10^-5 Ω•m, and the maximum power factor increased to 5.6 × 10^-2 W•m^-1•K^-2. The improved thermoelectric properties of Si/Ge nanostructured films are possibly attributable to the synergistic effects of interface scattering, interface barrier, and quantum dot localization.