Isotopically enriched silicon heterostructures and its thermoelectric properties

在这个研究项目的框架内，我们将对热电应用的硅同位素超晶格结构进行原理验证研究。利用分子束外延的方法，可以生长出未掺杂的、均匀的p型和n型掺杂的同位素富集硅多层结构。用高分辨率透射电镜测定外延质量。热处理前后同位素结构的深度剖面可以提供有关可能的瞬态扩散效应的信息，从而了解结构的热稳定性。电学性质将用范德波和霍尔效应测量来表征。热性能，如热容量，导热系数和扩散率将测量物理性能测量系统和激光闪光技术。在与外部团队的合作下，塞贝克系数的横向均匀性将用电位-塞贝克探针技术进行映射，光激发同位素超晶格的晶格动力学将用时间分辨x射线散射进行研究。最后，将制作由n型硅和p型硅组成的热电模块，以测试热电材料的同位素超晶格的总体增益。各种理论研究将伴随我们的实验，以更好地了解同位素超晶格的热性质。

In the framework of this research project we will perform proof-of-principle investigations of silicon isotope superlattice structures for thermoelectric applications. Undoped and homogenously p- and n-type doped isotopically enriched silicon multilayer structures will be grown by means of molecular beam epitaxy. The epitaxial quality will be determined with high resolution transmission electron microscopy. Depth profiling of the isotope structure before and after thermal treatments yields information about possible transient diffusion effects and thus about the structure thermal stability. The electrical properties will be characterized with van-de Pauw and Hall Effect measurements. Thermal properties such as the heat capacity, thermal conductivity and diffusivity will be measured with a physical property measurements system and a laser flash technique. In collaboration with external groups the lateral homogeneity of the Seebeck-coefficient will be mapped with a potential-Seebeck-probe technique and the lattice dynamics of the the optically excited isotope superlattice is investigated with time-resolved x-ray scattering. Finally, thermoelectric modules consisting of n- and p-type silicon with and without an isotope superlattice will be fabricated to test the overall gain of isotope superlattices for thermoelectric materials. Various theoretical investigations will accompany our experiments to better understand the thermal properties of the isotope superlattice.