Berlin 2018 – scientific programme

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DS: Fachverband Dünne Schichten

DS 15: Thermoelectric and Phase Change Materials

DS 15.1: Talk

Tuesday, March 13, 2018, 11:45–12:00, E 020

Thermoelectric nanocrystalline SiGe thin films prepared by the combination of AIC and SiO2 reduction — •Marc Lindorf, Anna Zera, and Manfred Albrecht — Institute of Physics, University of Augsburg, Universitätsstraße 1, Augsburg, Germany

Classic thermoelectric materials like SiGe often face low efficiencies for practical applicability while also being held back by industrial inefficient preparation and implementation methods.

In this work, we present a thin film approach for the preparation of nanocrystalline SiGe. The process of aluminum induced crystallization (AIC) is utilized to transform sputter deposited amorphous Si80Ge20 on quartz glass (SiO2) in a polycrystalline state under the presence of Al. Parts of the Al are incorporated into the SiGe leading to p-type doping. The reduction of SiO2 by Al to Si and Al2O3 was used after the catalytic AIC process to remove the remaining metallic Al which otherwise would shortcut the thermoelectric SiGe layer [1].

The AIC processed SiGe thin films were structurally analyzed via Rutherford Backscattering Spectrometry, X-ray Diffraction, and Transmission Electron Microscopy before and after annealing. The Si atoms released by the reduction reaction were incorporated to the SiGe layer without forming a secondary phase. Furthermore, a thermoelectrically promising twin grained microstructure was found for the prepared SiGe. Electrical resistivity and Seebeck coefficient were characterized from room temperature up to 700 K revealing transport properties typical for degenerated semiconductors.

[1] M. Lindorf et al., J. Appl. Phys. 120, 205304 (2016)