Towards efficient RuO2 thermoelectric thin films through utilizing a quantum design approach

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RuO2 (rutile structure) exhibits a potential for thermoelectric applications due to its interesting transport properties. The objective of this work is to correlate composition, structure, and transport properties for RuO2 and RuO2 alloyed with Nb, Pd, and a lanthanide. Using ab initio calculations, we will probe the effect of all lanthanides as possible alloying elements for RuO2, on phase stability, Seebeck coefficient, and electrical conductivity thereof. Based on this quantum design approach, we will identify a suitable lanthanide and test this design proposal experimentally. Our experimental strategy is to investigate a large compositional range by combinatorial sputtering and analysis of chemical composition, structure, morphology, as well as bonding and then synthesize homogeneous thin films for Seebeck coefficient, thermal and electrical conductivity measurements. RuO2 nanorods can be formed by reactive sputtering and here we will explore the role of alloying on nanorod formation and hence transport properties. We will also carry out ab initio molecular dynamics simulations as well as plasma chemistry and energetics investigations of Ru-O2-Ar discharge to explore the underlying atomic-scale mechanisms. Hence, two routes to increase the figure of merit for RuO2 based thin films will be followed: (i) quantum confinement effects by alloying and (ii) enhanced phonon scattering by nanorod formation.