High thermoelectric performance in high crystallinity epitaxial Si films containing silicide nanodots with low thermal conductivity

High crystallinity Si films containing silicide nanodots (NDs) were epitaxially grown on Si substrates at high temperature (∼750 °C), where the silicide phase of NDs (metallic α-FeSi₂ or semiconductor β-FeSi₂) was selectable by tuning the Fe deposition amount. The high crystallinity high-temperature-grown Si films with NDs exhibited lower thermal conductivity (5.4 W m⁻¹ K⁻¹) due to the phonon scattering at the ultrasmall ND interfaces than bulk Si-silicide nanocomposites that have ever been reported. In this ND system with extremely low thermal conductivity, due to the less point defects and high quality ND interface, the thermoelectric power factor (∼28 μW cm⁻¹ K⁻²) was observed to be the same as the high value of Si films without NDs at room temperature, which is the highest value among Si-silicide bulk nanocomposites ever reported. The simultaneous achievement of a high power factor and low thermal conductivity in the high quality ND system will provide the key for design of high thermoelectric performance of Si-based nanostructured films.