Berlin 2015 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 14: Transport I: Diffusion

MM 14.7: Talk

Monday, March 16, 2015, 17:30–17:45, H 0107

Self-Diffusion in Amorphous Silicon Investigated by Neutron Reflectometry — •Florian Strauß¹, Harald Schmidt¹, Jochen Stahn², and Thomas Geue² — ¹TU Clausthal, AG Mikrokinetik, Institut für Metallurgie, Deutschland — ²Paul Scherrer Institut, Villigen, Schweiz

The characteristics of silicon self-diffusion in the amorphous state are still unknown, albeit the material is widely used in solar cells, flat screen displays and is looked at as a promising electrode material in Li-ion batteries. In this model system of a covalent amorphous semiconductor low diffusivities and intrinsic metastability necessitate the use of Neutron Reflectometry (NR) a method capable of determining diffusion lengths of 1 nm and below [1,2]. ²⁹Si/²⁸Si isotope multilayer structures are prepared by ion beam sputtering and thermally treated in an Ar atmosphere at temperatures up to 700 ^∘C in order to induce isotope-interdiffusion. The chemical homogeneity and amorphous structure are confirmed by cross-sectional TEM measurements and XRD data. At temperatures between 350 and 500 ^∘C a time dependent short range diffusion process on the length scale of 1 nm is observed and interpreted as a consequence of structural relaxation. At temperatures above 500 ^∘C diffusion over a range of several nanometres is found. Additional measurements by Secondary Ion Mass Spectrometry confirm the data obtained by NR.

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

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