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We report the thermoelectric characterization of Ru2Si3 thin films. Ruthenium (VI)-silicide was formed via silicidation by rapid thermal processing of ruthenium on amorphous, undoped silicon of different thicknesses (sub-50 nm). 300 mm wafer level processes were applied, utilizing physical and chemical vapor deposition methods. High-temperature-XRD, energy dispersive x-ray spectroscopy, transmission electron microscopy, and time-of-flight secondary ion mass spectrometry confirm the formation of single-phase Ru2Si3 thin films. Thermoelectric measurements reveal exceptionally high Seebeck coefficients of up to 1.5 mV/K close to room temperature in dependence of adjustable oxide nanoskins. Due to the thermal stability of the nanoskins, fine-tuning of the thermoelectric properties by rapid thermal processing could be applied in a large temperature range. [ABSTRACT FROM AUTHOR]

The thermoelectric properties of single-crystalline and polycrystalline FeGa3 are systematically investigated over a wide temperature range. At low temperatures, below 20 K, previously not known pronounced peaks in the thermal conductivity (400-800 W K-1 m-1) with corresponding maxima in the thermopower (in the order of -16000 μV K-1) were found in single-crystalline samples. Measurements in single crystals along [100] and [001] directions indicate only a slight anisotropy in both the electrical and thermal transports. From susceptibility and heat-capacity measurements, a magnetic or structural phase transition was excluded. Using density functional theory based calculations, we have revisited the electronic structure of FeGa3 and compared the magnetic (including correlations) and nonmagnetic electronic densities of states. Thermopower at fixed carrier concentrations is calculated using semiclassical Boltzmann transport theory, and the calculated results match fairly with our experimental data. The inclusion of strong electron correlations treated in a mean field manner (by LSDA + U) does not improve this comparison, rendering strong correlations as the sole explanation for the low-temperature enhancement unlikely. Eventually, after a careful review, we assign the peaks in the thermopower as a manifestation of the phonon-drag effect, which is supported by thermopower measurements in a magnetic field. [ABSTRACT FROM AUTHOR]

Abstract: A systematic investigation on tuning the charge carrier concentration by substitution of the Ru position in RuIn3 is performed. Samples with nominal composition Ru0.95 T 0.05In3 (T=Re, Rh, Ir) were synthesized via liquid–solid-reaction and subsequent spark plasma sintering treatment. The chemical composition was characterized by X-ray, metallographic and microstructure analysis revealing solid solutions in the samples with Rh and Ir, whereas Re cannot be incorporated in RuIn3. Minor oxide impurities in the commercially available starting elements, the homogeneity range of RuIn3 and the redox potentials of the participating elements are the key for interpreting the observed lattice parameters and the corresponding composition. Both, substitutions with Rh or Ir and Re inclusions in RuIn3 lead independently to a significant decrease of the total thermal conductivity down to approximately one half of the value observed for binary RuIn3, prepared with commercially available starting materials. The electrical resistivity was reduced by substitution and the temperature dependence changes from semiconductor-like, for RuIn3, to metal-like in the substitution derivatives. At the same time the sign change in the thermopower at high temperatures, characteristic for binary RuIn3, is suppressed, attaining only electrons as majority carriers. [Copyright &y& Elsevier]