Fast phase transition process of Ge2Sb2Te5 film induced by picosecond laser pulses with identical fluences

Fast phase transition processes on Ge2Sb2Te5 film induced by picosecond laser pulses were studied using time-resolved reflectivity measurements. It was found that after picosecond laser pulse priming, reversible switching could be occurred upon picosecond laser pulse irradiation with the same well-chosen fluence. This is very different from general knowledge that reversible phase change process will be induced by laser pulses with different powers; that is, amorphization process needs much higher fluence than crystallization process. The possible mechanism was discussed qualitatively by a melting-cooling model.