KINETICS OF GRAIN-BOUNDARY REACTIONS AT SEMIMETAL-SEMICONDUCTOR INTERFACES OBSERVED DURING IN-SITU TRANSMISSION ELECTRON-MICROSCOPE ANNEALING

The effects of annealing on Ge/Sb/Ge trilayer thin films consisting of amorphous Ge and polycrystalline Sb layers have been studied by in-si tu heating in a transmission electron microscope. The results show tha t reactions are triggered at the grain boundaries (GBs) of the crystal line Sb layer and are accompanied by crystallization of the Ge and dif fusion of Sb away from the GBs. The broadening of the reacted region w ith time t is well fitted by a t(1/2) law, leading to GB diffusion coe fficients which are two orders of magnitude higher along the GBs than across them, the value across the GBs being two orders of magnitude hi gher than the tabulated diffusion coefficient of Sb into crystalline G e extrapolated to the temperatures used in this work. Finally, the app licability of the Johnson-Mehl-Avrami theory to analyse the reaction k inetics in layered films will be discussed.