Solidification phenomena in Ge films upon nano- and pico-second laser pulse melting

Melting has been induced in amorphous Ge films upon irradiation with both nano- and pico-second laser pulses. The role of undercooling and heat flow in the subsequent rapid solidification process has been investigated by analyzing the behavior of films with different thicknesses (30–180 nm) grown on Si(100) substrates by means of real time reflectivity measurements in the ns timescale. Recalescence is observed in films with a thickness above a threshold value which depends on the pulse duration. An additional solidification scenario, i.e. surface initiated solidification, is observed upon ps pulse irradiation in films with intermediate thicknesses.