Pulsed-laser-induced microcrystallization and amorphization of silicon thin films

Pulsed-laser-induced microcrystallization and amorphization of Si thin films were investigated by transient reflectance and conductance measurements. It was clarified experimentally that the complete melting of a Si film and subsequent supercooling induces both microcrystallization and amorphization. In the case of the microcrystallization of a 49.1-nm-thick Si film, nucleation among supercooled liquid Si was observed. The nucleation temperature and resulting nucleation rate under the microcrystallization condition were estimated to be 1047 K and 1.67 x 10(25) events/(cm(3).s), respectively. On the other hand, no significant nucleation was observed in the case of a laser amorphization of 20.7-nm-thick Si film although the film was melted for the relatively long duration of about 80 ns. Extremely fast quench of liquid Si films seems to suppress nucleation and results in solidification in amorphous phase.