Wetting Angles and Surface Tension in the Crystallization of Thin Liquid Films

Abstract

ABSTRACTThe behaviour of thin liquid films is known to be dominated by surface tension forces. We show that the crystallization of thin liquid films requires that two wetting angle conditions be simultaneously satisfied: (i) relating to the liquid–vapour interface and (ii) relating to the crystal–liquid interface. The balance between capillary pressure and thermal gradient forces shows that the equilibrium freezing point of thin films is actually depressed below the bulk freezing point. The magnitude of the effect is 1°K in an 800 Å thick film. These observations suggest that small–scale thickness fluctuations may be responsible for the initiation of sub–grain boundaries in the growth of crystalline silicon films.