Picosecond laser induced anomalous crystallization in amorphous silicon

Two different values of thresholds for crystallization of amorphous silicon were observed by using picosecond laser pulses. One of the crystallization thresholds is found experimentally to be clearly below the amorphization threshold. The other crystallization threshold is well above the amorphization threshold. Additionally, small changes of surface height are observed even at the unannealed region far outside the central annealed region. These results imply that shock stress generated by picosecond heating is important in the crystallization process.