Structural and thermoelectric characterization of individual single-crystalline nanowires

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The thermoelectric transport of semiconductor nanowires based on V-VI materials (Sb2Te3, Bi2Te3 and related ternary alloys) and one IV-VI material (PbTe) as a reference for high temperature measurements will be investigated. By engineering the doping level and surface morphology during and after the nanowire growth, bulk-like power factors and reduced thermal conductivities in comparison to the bulk counterparts should be achieved. The core of the project development is a measurement platform with integrated heaters and electrodes for advanced measurements and spatial manipulation of nanowires (NWs). This device is based on MEMS technology, which can be applied for low-temperature measurements and investigations in transmission electron microscopes (TEM). The individual nanowire will be placed on the MEMS platform. The electrical connection between the NWs and the platform is made in a last step, with a focus on developing a method which does not need any further microfabrication steps. Systematic measurements of the thermal conductivity as function of the nanowire diameter and the surface morphologies and structures will be carried out. Full ZT-characterization from 2 to 673 K will be performed with the thermoelectric characterization platform. Furthermore, the charge carrier mobility and density of gated nanowires at low temperature will be determined. The project goal will be a data correlation between the thermoelectric measurements, theoretic calculations, advanced chemical and TEM analysis from single nanowires and accompanying studies on the thermal stability of Bi2Te3/Sb2Te3 based nanostructures by tight collaborations within the SPP.