纳米线阵列结构碲化铋基热电材料的费米面与界面调控及输运性能研究

Thermoelectric (TE) semiconductor materials can convert heat to electricity, and vice versa. The conversion efficiency depends largely on the material's TE properties, which are often summarized by the figure of merit ZT. To overcome the bottleneck of relatively low TE conversion efficiency, it is an effective pathway through design and use of nanowire array TE materials. Especially, The shape and size of Feimi surfaces and special interfaces control show a promising prospects in improvment of TE material properties in recent. In this proposal, Bi2Te3 based nanowire arrays would be successfully self-assembled on substrates by a simple thermal evaporation or magnetron sputtering or ion beam assisted deposition method. Adjusting the evaporated current, substrate temperature, buffer layer etc., we attempt to improve the transport properties of carries and phonons by controlling the nanowire diameter, distance between nanowires, angle of inclination, composition etc., and optimizing the shape and size of Feimi surfaces and interfaces. A TE dimensionless figure-of-merit of films should be greatly enhanced and ZT>1.7 near room temperature due to the optimized Fermi surfaces and the occurrence of quantum size effect and interface scattering effect leading to the enhancement of Seebeck coefficient and increased interface scattering of phonons to reduce the thermal conductivity. Various nanowire array microstructures, constructed by using nanowires as building blocks, may provide an effective pathway towards the systematic contol of the shape and size of Feimi surfaces and interfaces, leading to improvement of materials properties, which can provide valuable new idea and crucial scientific significance in studies of TE materials.

热电半导体材料是可以实现热能与电能相互转换的功能材料，而其热电转化效率主要依赖材料ZT值，为了克服目前相对低的转换效率的瓶颈，纳米线阵列结构的设计与加工是提升其性能的一个重要途径，尤其纳米线阵列的费米面的形状、大小与特殊界面的设计，可使热电材料性能获得突破。本申请以碲化铋基热电块体材料为原料，采用简便的真空蒸镀或磁控溅射或离子辅助沉积法可控组装纳米线阵列材料。通过调节工艺参数和利用过渡层与附加电压的诱导手段，调控纳米线的直径、成分、线间距、纳米线与基底的倾斜度等，最优化材料体系的费米面的形状、大小与界面，实现载流子和声子的输运协同调控与热电性能的提高。通过优化费米面、量子尺寸效应与界面散射效应，目的是使纳米阵列材料性能在室温附近ZT>1.7。基于这种纳米线结构单元构建，实现材料的费米面的形状、大小与特殊的界面调控，从而使得热电材料性能得到提高，为今后研究打下实验与理论基础。

热电半导体材料是可以实现热能与电能相互转换的功能材料，而其热电转化效率主要依赖材料ZT值。理论与实验分析表明低维结构能极大地优化电子与声子的输运，尤其纳米线阵列的费米面与特殊界面的设计，可使热电材料性能获得突破。本项目以碲化铋基热电块体材料为原料，采用简便的真空蒸镀或磁控溅射法可控组装纳米线阵列材料。通过调节工艺参数和利用过渡层与附加电压的诱导手段，调控纳米线的直径、线间距、纳米线与基底的倾斜度、成分等，最优化材料体系的费米面与界面，实现载流子和声子的输运协同调控与热电性能的提高。通过优化费米面、量子尺寸效应与界面散射效应，按照课题要求开发了几种新型热电材料，完成了纳米线阵列的制备工艺研究，制备出性能优异的薄膜材料，性能达到预期的指标，已经获得45°倾斜生长的(Sb,Bi)2Te3纳米阵列材料性能ZT=1.72在室温条件，这一结果已达到了目前国内外低温热电材料领先水平。这些方法为优化纳米结构薄膜开辟新的途径，实现材料的费米面与特殊的界面调控，从而使得热电材料性能得到提高，为研究下一代热电材料与器件打下实验与理论基础。