Research on Si based thermoelectric material by nanostructuring

本研究的目的是探索提高环境负荷较低的纳米结构硅的热电转换效率的可能性。关键是控制声子输运，通过降低导热系数来获得更高的性能。我们挑战了基于声子的人工控制导热系数。开发了小至100 nm周期的气悬式硅纳米结构的形成技术。研制了一种用于微纳米结构导热系数测量的高通量、高可靠性的时域微热反射系统。我们成功地观察到了声子在纳米结构中的室温弹道输运，与纳米线相比，声子晶体纳米结构的导热系数明显降低。结果表明，该结构在导热工程中具有一定的实用价值。

The objective of this research is investigation of the possibility of enhancement of the thermoelectric conversion efficiency of nanostructured Si, which has low environmental load. The key is control of phonon transport, which results in higher performance by reducing the thermal conductivity.We challenged the artificial control of thermal conductivity on the basis of phononics. Formation technology of as small as 100-nm-period air-suspended Si nanostructure has been developed. A high through put and reliable time-domain micro thermoreflectance system for thermal conductivity measurements for micro/nano structures has been developed. We have succeeded in observing a characteristic ballistic phonon transport at room temperature in nanostructures and clear reduction in thermal conductivity in phononic crystal nanostructures compared with those in nanowires. This result shows that this structure is useful for thermal conduction engineering.