Institute of Industrial Science, University of Tokyo, Tokyo, 153-8505, Japan.
Nanoscale. 2017 Oct 12;9(39):15083-15088. doi: 10.1039/c7nr05114j.
In search of efficient thermoelectric nanostructures, many theoretical works predicted that nanopillars, placed on the surface of silicon membranes, nanobeams, or nanowires, can reduce the thermal conductivity of these nanostructures. To verify these predictions, we experimentally investigate heat conduction in suspended silicon nanobeams with periodic arrays of aluminium nanopillars. Our room temperature time-domain thermoreflectance experiments show that the nanobeams with nanopillars have 20% lower thermal conductivity as compared to pristine nanobeams. We discuss possible explanations of these data, including coherent effects, and conclude that the thermal conductivity is reduced mainly by phonon scattering at the pillar/beam interface due to the intermixing of aluminium and silicon atoms, as supported by the transmission electron microscopy. As this intermixing does not only reduce thermal conductivity but may also increase electrical conductivity, these nanostructures are exceptionally promising for thermoelectric applications.
为了寻找高效的热电纳米结构，许多理论工作预测，硅膜、纳米梁或纳米线上的纳米柱可以降低这些纳米结构的热导率。为了验证这些预测，我们通过实验研究了具有周期性铝纳米柱阵列的悬空硅纳米梁中的热传导。我们的室温时域热反射率实验表明，与原始纳米梁相比，具有纳米柱的纳米梁的热导率降低了 20%。我们讨论了这些数据的可能解释，包括相干效应，并得出结论，由于铝和硅原子的混合，热导率主要通过柱/梁界面处的声子散射而降低，这得到了透射电子显微镜的支持。由于这种混合不仅降低了热导率，而且可能增加了电导率，因此这些纳米结构在热电应用中具有非常大的应用前景。
