Thermoelectric devices can impact the energy issue because they can be used to convert waste heat into useful electrical energy. Thermoelectrics for energy harvesting necessitates the discovery of materials with high power factor (determined by the Seebeck coefficient and the electrical conductivity) and low thermal conductivity. But, these two properties are usually dependent and difficult to tune separately. However, the electron confinement and, consequently, the quantization of the carrier energy in one or more directions are predicted to enhance the power factor of 2D and 1D structures. Simultaneously, a decrease of thermal conductivity with respect to the bulk material is expected due to the increased boundary scattering. These expectations have led to an enormous increase in the research on thermal transport in nanowires.

I propose to utilize nanostructured materials as efficient thermoelectric materials. More specifically, I propose to enhance the thermoelectric performances of already promising nanowires with the design and realization of “nanowire-composites” and “topological thermoelectric nanowires”. I believe that these nanowire based nanostructures are ideal with respect to the decoupling of thermal and electronic transport, which will be a breakthrough in the field of thermoelectrics. They provide an increased amount of interfaces and surfaces, which is crucial to enhance phonon scattering with a resulting lower thermal conductivity. Additionally, these complex nanowire heterostructures provide a template for the engineering of high mobility electron channels, resulting in the effective enhancement of the power factor. I want to assess the thermoelectric properties of individual nanowire based heterostructures with the use of suspended SiNx membranes with implemented heaters. Furthermore, I want to explore the phonon transport by means of time resolved Raman spectroscopy. The proposed research claims to be of great relevance for fundamental research as well as for technological applications.