Explosive Crystallization in A-Ge Films Irradiated with Microsecond Laser Pulses

Abstract

ABSTRACTExplosive crystallisation has been observed in deposited a-Ge films irradiated with pulsed Nd-glass laser beam of 400 micro second duration. Transmission electron microscopic examination of the irradiated film shows a polycrystalline region surrounded by radial dendrites of ~ 8-10 ;Cm size. Analysis of the results is consistent with the duplex-melting model of the explosive crystallisation mechanism. Heat released during the amorphous to crystalline transformation of a localised region abruptly crystallises the surrounding area resulting in dendritic growth. The crystallisation is self-sustaining untill the temperature ahead of liquid/amorphous interface drops below 775 K. These results are consistent with earlier study of explosive crystallisation in unsupported a-Ge films and further confirm that the heat loss to the underlying substrate governs the dynamics of the crystallisation process.