The rate at which crystalline-Si nucleates at the amorphous-Si/liquid-Si interface is estimated. On the basis of this estimate and physical arguments, we propose that under certain conditions a moving amorphous-Si/liquid-Si interface is unstable with respect to nucleation of crystalline Si. Such nucleation, followed by growth, is a possible mechanism for the well-known explosive crystallization of amorphous Si. Furthermore, a similar instability can explain the formation of amorphous Si from liquid Si.

• Received 4 December 1986

DOI:https://doi.org/10.1103/PhysRevLett.58.2782