Rewritable phase-change optical recording in Ge2Sb2Te5 films induced by picosecond laser pulses

Abstract

The phase transformation dynamics induced in ${\mathrm{Ge}}_2{\mathrm{Sb}}_2{\mathrm{Te}}_5$ films by picosecond laser pulses were studied using real-time reflectivity measurements with subnanosecond resolution. Evidence was found that the thermal diffusivity of the substrate plays a crucial role in determining the ability of the films to crystallize and amorphize. A film/substrate configuration with optimized heat flow conditions for ultrafast phase cycling with picosecond laser pulses was designed and produced. In this system, we achieved reversible phase transformations with large optical contrast $\text{(>20\%)}$ using single laser pulses with a duration of 30 ps within well-defined fluence windows. The amorphization (writing) process is completed within less than 1 ns, whereas crystallization (erasing) needs approximately 13 ns to be completed.