DOI: 10.1209/epl/i1996-00473-7

Europhys. Lett, 34 (6), pp. 423-428 (1996)

High undercooling of bulk molten silicon by containerless processing

D. Li and D. M. Herlach

Institut für Raumsimulation, Deutsche Forschungsanstalt für Luft- und Raumfahrt, D-51140 Köln, Germany

(received 12 February 1996; accepted 3 April 1996)

PACS. 64.70Dv - Solid-liquid transitions.
PACS. 81.30Fb - Solidification.

Abstract:

When containerless electromagnetic levitation processing was applied to elemental semiconductor Si using a two-step heating method proposed by the present authors, a substantial degree of undercooling up to 420 K (, is the melting temperature, 1685 K for Si) has been reproducibly achieved in slowly cooled silicon droplets ( in diameter). The microstructural change from faceted twins grown at low or intermediate undercoolings to twin-free grains formed at high undercoolings indicates a transition of solidification mechanisms. The experimental results, of which both the undercooling level and the sample volume surpass the previous work, lead to a reassessment of the nucleation frequency and the crystal/melt interfacial energy of undercooled Si liquid.

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