Crystallization-front velocity during scanned laser crystallization of amorphous Ge films

An optical transmission technique is used to measure the propagation velocity of the crystallization front during scanned laser crystallization of amorphous Ge films on fused-silica substrates. The measurements confirm a theoretical model for the solid-phase amorphous-to-crystalline transformation. According to this model, the periodic structural features of the crystallized films are formed because the crystallization front moves in a series of periodic jumps between rest positions, with the velocity of the front during each jump much higher than the laser scanning velocity. The measured values of the crystallization front velocity range from 140 to 260 cm/sec, compared with the laser scanning velocity of only 0.5 cm/sec.