Crystallization process corresponds to an erasing or a set operation in phase change optical storage or phase change electrical memory. Short crystallization time will be favorable for obtaining high data transfer rate. Thus searching for materials with faster crystallization rate and shorter crystallization time is very important to improve the performance of phase change data storage.

Researchers at Shanghai Institute of Optics and Fines Mechanics (SIOM/China) studied the transient phase change crystallization process of SiSb phase change thin films under the irradiation of picosecond (ps) laser pulse using time-resolved reflectivity measurements. [Materials Chemistry and Physics 128, 405–409, (2011)]

They studied crystallization dynamics of as-deposited amorphous Si15Sb85 thin films induced by picosecond laser pulses with different fluences using time-resolved reflectivity measurements. Above the crystallization threshold fluence, the crystallization process was shown to be a recalescence-involved process. The topographies, Raman spectra and optical constants of both as-deposited amorphous state and irradiated crystalline state of SiSb were studied. A reflectivity contrast of about 15% in the visible light region can be achieved by ps laser pulse-induced crystallization. The whole crystallization time can only be slightly shortened by an additional thermally conductive silver underlayer(from about 64 ns to 59 ns). But after primed with low-fluence laser pulse, the crystallization time can be greatly reduced (from 59 ns to 11 ns) and the crystallization process becomes a monotonic rising process. SiSb was confirmed to be a very promising candidate for high-speed or ultrafast phase change data storage applications.