SOLIDIFICATION PHENOMENA IN GE FILMS UPON NANO-SECOND AND PICO-SECONDLASER-PULSE MELTING

Melting has been induced in amorphous Ge films upon irradiation with b oth nano- and pico-second laser pulses. The role of undercooling and h eat flow in the subsequent rapid solidification process has been inves tigated by analyzing the behavior of films with different thicknesses (30-180 nm) grown on Si(100) substrates by means of real time reflecti vity measurements in the ns timescale. Recalescence is observed in fil ms with a thickness above a threshold value which depends on the pulse duration. An additional solidification scenario, i.e. surface initiat ed solidification, is observed upon ps pulse irradiation in films with intermediate thicknesses.