The effect of finite film thickness on the crystallization kinetics of amorphous film and microstructure of crystallized film

摘要

A model for crystallization kinetics of thin amorphous film is developed by extension the Kolmogorov-Johnson-Mehl-Avrami (KJMA) model to take into account a finite film thickness. Two model versions, volume induced crystallization (VIC) and surface induced one (SIC), are explored. Finite film thickness effects lead to important consequences in the VIC: the crystallization profile reaches maximum in film middle, the crystallites population in a film is always higher than in a bulk material, the thinner film the slower it crystallizes and a spatially inhomogeneous structure with a fine-grained subsurface layer is formed. A VIC-kinetics follows a generalized KJMA equation with parameters depending on a film thickness and a range of the KJMA model validity is found. A SIC-kinetics obeys 2D KJMA equation hi sufficiently thin film and is almost linear in a thick film. The model is extended to the case of non-constant growth rate and crystallization of subsurface film layer, and is shown to be consistent with experimental data.