Regensburg 2013 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 20: Transport & Diffusion I

MM 20.5: Vortrag

Dienstag, 12. März 2013, 11:15–11:30, H26

Experiments on the Investigation of Self-Diffusion in Amorphous Silicon — •Florian Strauß¹, Harald Schmidt¹, Jochen Stahn², and Thomas Geue² — ¹TU Clausthal, AG Mikrokinetik, Institut für Metallurgie, Deutschland — ²Paul Scherrer Institut, Villigen, Schweiz

A key task in material science is the investigation of self-diffusion in solids in order to characterize kinetic processes and to identify point defects and process relevant activation energies. In spite of its technological importance, e.g. in photovoltaic cells, there are no experimental data in current literature on the self-diffusion in amorphous silicon (a-Si). This is mainly due to a combination of the expected low diffusivities and the intrinsic metastability of a-Si in the accessible time and temperature range. In order to determine self-diffusivities ²⁹Si/²⁸Si isotope multilayers are prepared by ion-beam sputtering. Afterwards those samples are thermally treated in Ar atmosphere at different temperatures below the crystallization limit in order to induce diffusion. The isotope multilayers are amorphous and chemically homogeneous (as shown by TEM and XRD) but isotope-modulated. Consequently diffusion can be measured by time-of-flight neutron reflectometry, a method capable of determining extremely small diffusion lengths in the order of 1 nm and below [1,2]. First results point to an onset of diffusion at about 350 ^∘C. The influence of O impurities on structure and diffusion is discussed.

[1] H. Schmidt et al.; Acta Mater. 56 (2008), 464

[2] E. Hüger et al., Appl. Phys. Lett. 93 (2008), 162104