CRUCIBLE DE-WETTING DURING BRIDGMAN GROWTH IN MICROGRAVITY .2. SMOOTHCRUCIBLES

On the basis of experimental results, it has been considered that semi conductors can present very high contact angles on crucible materials, due to slight amounts of pollution by residual gases. This phenomena is used to explain the de-wetting of semiconductors observed when grow n under microgravity conditions in smooth crucibles. Another phenomena based on pressure differences between the hot and cold sides of the l iquid can explain dewetting in the case of thermodynamic wetting angle s, even in the case of metals and on the ground. The effect of various parameters such as contact angle, growing angle, crystal radius and p ressure difference have been studied and a stability analysis has show n that the growth process is stable for high contact angles. For low c ontact angles, the growth is not stable, but the high pressure differe nces needed to get reasonable values of the gap thickness between the wall and the crucible can have a stabilizing effect.