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Kojda D.,Humboldt University Berlin12489 BerlinGermany | Mitdank R.,Humboldt University Berlin12489 BerlinGermany | Weidemann S.,Humboldt University Berlin12489 BerlinGermany | Mogilatenko A.,Ferdinand - Braun - Institute | And 7 more authors.
Physica Status Solidi (A) Applications and Materials Science | Year: 2015

Abstractauthoren Abstractauthoren Metallic and semiconducting nanowires (NWs) are of interest in the field of thermoelectrics, because they act as model system to investigate the influence of surfaces on the thermoelectric transport properties. In single crystalline NWs, the grain boundary scattering is negligible and the surface-to-volume-ratio is high. We present state-of-the-art of the combination of the structural, chemical, and temperature-dependent full thermoelectric characterization for individual single crystalline NWs, which is essential to conclude on surface effects. Temperature-dependent measurements allow further conclusions on the scattering mechanisms. Simulations by the finite element method are performed on indented NWs to interpret the measurement results. Calculated surface temperature of a single-indented and a multi-indented NW. Combined thermoelectrical, structural and chemical characterisation of individual metallic and semiconducting nanowires is presented. In the temperature range between 4.2 K and room temperature the thermoelectrical properties are determined. Transmission electron microscopy yields the structural properties, the chemical composition and the morphology of the nanowires. This comprehensive study unambiguously allows identifying surface effects on the thermoelectric properties and scattering mechanisms for electrons and phonons. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim October 2015 10.1002/pssa.201532464 Feature Article Feature Articles © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Riha C.,Humboldt University Berlin12489 BerlinGermany | Chiatti O.,Humboldt University Berlin12489 BerlinGermany | Buchholz S.S.,Humboldt University Berlin12489 BerlinGermany | Reuter D.,University Paderborn33098 PaderbornGermany | And 2 more authors.
Physica Status Solidi (A) Applications and Materials Science | Year: 2016

Low-dimensional transport in semiconductor meso- and nanostructures is a topical field of fundamental research with potential applications in future quantum devices. However, thermal non-equilibrium may destroy phase-coherence and remains to be explored experimentally. Here, we present effects of thermal non-equilibrium in various implementations of low-dimensional (non-interacting) electron systems, fabricated by etching AlGaAs/GaAs heterostructures. These include narrow quasi-two-dimensional (2D) channels, quasi-one-dimensional (1D) waveguide networks, quantum rings (QRs), and single 1D constrictions, such as quantum point contacts (QPCs). Thermal non-equilibrium is realized by current heating. The charge carrier temperature is determined by noise thermometry. The electrical conductance and the voltage-noise are measured with respect to bath temperatures, heating currents, thermal gradients, and electric fields. We determine and discuss heat transport processes, electron-energy loss rates, and electron-phonon interaction, and our results are consistent with the Wiedemann-Franz relation. Additionally, we show how non-thermal current fluctuations can be used to identify electric conductance anomalies due to charge states. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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