Abstract
Femtosecond laser-induced ultrafast crystallization in 80 nm as-deposited Ge 2 Sb 2 Te 5 films has been investigated by time-resolved microscopy. With an average fluence of approximately 10 mJ/cm 2 , a transient nonequilibrium state of the excited material was formed within 2 ps. The results can be interpreted as an electronically induced nonthermal phase transition.