No abstract

The high electrical and drastically-low thermal conductivities, a vital goal for high performance thermoelectric (TE) materials, are achieved in Si-based nanoarchitecture composed of Si channel layers and epitaxial Ge nanodots (NDs) with ultrahigh areal density (~1012 cm−2). In this nanoarchitecture, the ultrasmall NDs and Si channel layers play roles of phonon scattering sources and electrical conduction channels, respectively. Electron conductivity in n-type nanoacrhitecture shows high values comparable to those of epitaxial Si films despite the existence of epitaxial NDs. This is because Ge NDs mainly scattered not electrons but phonons selectively, which could be attributed to the small conduction band offset at the epitaxially-grown Si/Ge interface and high transmission probability through stacking faults. These results demonstrate an independent control of thermal and electrical conduction for phonon-glass electron-crystal TE materials by nanostructure designing and the energetic and structural interface control.

Thermoelectric power factor enhancement through thermal management with resonant level effect is experimentally demonstrated in SiGeAu composite system.

No abstract

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.