Combined structural and electronic characterization on the micro/nanoscale of magnesium silicide-based materials using Kelvin probe force microscopy, first principle calculations and SEM/EDX

Kurzfassung

Thermoelectric generators can convert waste heat into useful electricity. Magnesium silicide-based materials have been established as promising cheap, environment-friendly materials with excellent thermoelectric properties in the mid-temperature range. Controlled unmixing of the solid solutions can be used in an advantageous manner by forming nanostructures in situ. Nanostructures can reduce the lattice part of the thermal conductivity by enhanced phonon scattering and improve electronic properties by blocking low energy charge carriers at the interfaces. Hence, the objective is to exploit and quantify energy filtering of the charge carriers for further performance optimization. Kelvin probe force microscopy (KPFM) measures the local contact potential difference between the probe tip and sample surface with sub-nanometer resolution. The combination of KPFM and scanning electron microscopy will allow a nanoscale correlation between the local work functions and topography of multiphase materials. Ab initio calculations of Fermi level (differences) between materials will assist in the interpretation of the measured work functions with the aim to get locally resolved carrier concentrations and eventually to quantify the impact of energy filtering.