Dresden 2014 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 27: Transport I - Materials/Methods

MM 27.5: Talk

Tuesday, April 1, 2014, 12:45–13:00, IFW B

Short Range Silicon Migration in Amorphous Silicon Observed 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

Amorphous silicon (a-Si) is a simple model system of covalent amorphous semiconductors, widely used in solar cells and flat screen displays and a promising electrode material in Li-ion batteries. Yet, there exist no experimental data on self-diffusion in the amorphous state. The expected low diffusivities and intrinsic metastability of a-Si require measurement by time-of-flight neutron reflectometry (NR), a method capable of determining diffusion lengths of 1 nm and below [1,2]. ²⁹Si/²⁸Si isotope multilayers are prepared by ion beam sputtering and thermally treated in Ar atmosphere at temperatures below the crystallisation temperature in order to induce interdiffusion. The samples are isotope modulated but amorphous and chemically homogenous as shown by TEM and XRD. Previous measurements have pointed to an onset of movement above 350 ^∘C and short range atomic diffusion processes on the length scale of 1.5 - 2 nm. New data from NR and SIMS are discussed, focussing on time dependent diffusion processes and long range motion at temperatures between 400 ^∘C and 600 ^∘C. The influence of impurities on diffusion and structure is also part of the on-going investigation.

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

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