High undercooling of bulk molten silicon by containerless processing
Institut für Raumsimulation, Deutsche Forschungsanstalt für
Luft- und Raumfahrt, D-51140 Köln, Germany
Accepted: 3 April 1996
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 (, Tm 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.
PACS: 64.70.Dv – Solid-liquid transitions / 81.30.Fb – Solidification
© EDP Sciences, 1996