Kinetics of grain-boundary reactions at semimetal-semiconductor interfaces observed during in-situ transmission electron microscope annealing

Abstract

The effects of annealing on Ge/Sb/Ge trilayer thin films consisting of amorphous Ge and polycrystalline Sb layers have been studied by in-situ heating in a transmission electron microscope. The results show that reactions are triggered at the grain boundaries (GBs) of the crystalline Sb layer and are accompanied by crystallization of the Ge and diffusion of Sb away from the GBs. The broadening of the reacted region with time t is well fitted by a t ^1/2 law, leading to GB diffusion coefficients which are two orders of magnitude higher along the GBs than across them, the value across the GBs being two orders of magnitude higher than the tabulated diffusion coefficient of Sb into crystalline Ge extrapolated to the temperatures used in this work. Finally, the applicability of the Johnson–Mehl–Avrami theory to analyse the reaction kinetics in layered films will be discussed.