Surface Undulations in Explosive Crystallization: A Thermal Instability

It is argued that surface undulations observed after self-sustained rapid crystallization of amorphous films result from a thermal instability that induces a periodically varying crystallization rate. Its physical origin is discussed for a simple nonlinear heat-conduction model which yields good agreement with experimental observations. A numerical analysis of the nonlinear oscillations shows that these may, in turn, bifurcate via a series of period-doubling bifurcations.