Ultrafast Structural Change in A GeSbTe Thin Film Induced by A Single Femtosecond Laser Pulse

Abstract

We demonstrated amorphization of a GeSbTe (GST) thin film through a non-melting process by femtosecond electronic excitation. Amorphous recording marks were formed by irradiation with single femtosecond pulses. These recording marks were confirmed to be recrystallized by laser annealing. Scanning electron microscope observations revealed that amorphization occurred below the melting temperature. We performed femtosecond pump-probe measurements to investigate the amorphization dynamics of a GST thin film. We found that the reflectivity dropped abruptly within 500 fs after excitation by a single pulse and that a small change in the refl ectivity occurred within 10 ps of this drop in reflectivity. We also discuss the mechanism of local amorphization evaluating the number of photoexcited electrons required for minimum unit that forms amorphous state.