Dresden 2011 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 22: Topical Session TEM VI
MM 22.3: Vortrag
Mittwoch, 16. März 2011, 12:00–12:15, IFW B
In-situ Transmission Electron Microscopy of Material Transport and Crystallization during the Al induced layer exchange (ALILE) process — •Balaji Birajdar1, Tobias Antesberger2, Martin Stutzmann2, and Erdmann Spiecker1 — 1Center for Nanoanalysis and Electron Microscopy (CENEM), Materials Science Department VII, University of Erlangen-Nürnberg, Germany — 2Walter Schottky Institut and Physics Department, Technische Universität München, Germany
The ALILE process enables fabrication of thin polycrystalline Si films at relatively low temperatures, making it highly promising for applications in thin film photovoltaics. While the driving forces for the metal-induced crystallization are rather well understood, the details of the material transport during the layer exchange are largely unknown. In this work, the microstructure of a stack of a-Si(100nm)/Al(50nm)/quartz, annealed at 450°C, has been investigated at different length scales by combining optical microscopy, SEM, and TEM. The results indicate that the layer exchange and crystallization proceeds by forming 20-50 μm wide dendritic cells with Al deficient centers. Excessive upward transport of Al by epitaxial growth out of the existing Al grains into the a-Si was observed in a rim of about 10 μm width around these cells and, to a smaller extent even beyond. Using in-situ TEM, the lateral and vertical transport of Al at the expanding crystallization front could be directly visualized for the first time and is proposed to be caused by Coble-type diffusion of Al driven by the compressive stress in the Al layer.