| Summary: | 碩士 === 國立交通大學 === 材料科學與工程學系 === 101 === Nanostructure engineering been theoretically and experimentally proven as a practial strategy for thermoelectric materialshas for effectively enhancing thermoelectric figure of merits, ZTs (defined as σS2T /κ). By nanostructuring, not only could the largely created surface or interfaces inhibit the thermal conductivity (κ), but the power factor (σS2) could be improved through the induced quantum confinement. Antimony selenide (Sb2Se3) has a higher Seebeck coefficient (1800 μVK-1) and lower thermal conductivity (~2.7 Wm-1K-1) compared with the widely studied bismuth telluride (Bi2Te3) bulk and is thus considered as a promising alternate of the room-temperature thermoelectric materials for the next generation. However, to date, thermoelectric data realted to the Sb2Se3 nanostructures have less been reported. Therefore, growth of nanostructured Sb2Se3 becomes a very attractive and important research topic for approaching potentially outstanding thermoelectric performance.
In this work, by using pulsed laser deposition (PLD) techniques, a series of well-aligned nanostructured Sb2Se3 films was successfully prepared on insulated SiO2/Si substrates without prebuilt catalysts and templates. At least seven types of previously unreported Sb2Se3 nanostructures including nanoteeth, nanowings, nanorods, nanodecks, nanotweezers, nanocolumns, and nanotubes were reproducibly obtained via precisely controlling the substrate temperature and ambient pressures. The temperature-dependent growth seems to be reasonably explained by the well-known structure zone model (SZM) and self-catalyst enhanced vapor-liquid-solid (VLS) growth. Among these specimens, the Sb2Se3 nanowings show an excellent electrical conductivity of 750 Sm-1 at 400 oC, which is comparable to the reported value of an isolated nanowire (852 Sm-1). In addition, the room-temperature electrical conductivity of the Sb2Se3 nanoteeths is 4 to 5 orders higher that that of the non-nanostructured Sb2Se3 film. In this work we succeded in improving the electrical conductivity of Sb2Se3 film.
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