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Regensburg 2010 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 26: Poster Session

MM 26.72: Poster

Dienstag, 23. März 2010, 14:45–16:30, Poster C

Growth kinetics and morphology of silicon crystallites synthesized from metallic solution — •Thomas Teubner, Robert Heimburger, Nils Deßmann, Torsten Boeck, and Roberto Fornari — Leibniz Institute for Crystal Growth, Max-Born-Str. 2, 12489 Berlin

The growth of large Si crystallites on amorphous substrates at low temperatures is highly desirable for fabrication of thin film solar cells but it remains a very challenging task. We use a low melting metallic solvent for Si seeding as well as subsequent growth. Supersaturation of solvent droplets for seed generation is reached via influx of Si from vapor and can be controlled by deposition rate. In contrast, expansion of Si seed crystal has been performed in a separate steady state solution growth equipment applying hereby a temperature gradient between vertically stacked feeding source, solvent, and substrate. The temperature difference of about 10 K enables continuous flow of solute towards substrate and thus provides the necessary supersaturation of solution around seed crystals. {111} and {110} facets are thermodynamically flat at 873 K. Even the experimental supersaturation is not sufficient to provoke kinetic roughness. An estimate of ledge free energy for two-dimensional nuclei suggests that the undercooling necessary for nucleation rates of 1 µm−2s−1 is 45 K for {111} and 18 K for {110} facets. Therefore, two-dimensional nucleation on {111} facets seems to be unlikely. The grown {111} faceted crystals are often twinned and partly exhibit hopper morphology. The latter can be explained by spreading of steps from apexes and edges and by spatial solute inhomogeneity.

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