Kinetics of volume and surface driven crystallization in thin films

Area of Science:

• Materials Science
• Physical Chemistry
• Condensed Matter Physics

Background:

• The Kolmogorov-Johnson-Mehl-Avrami (KJMA) theory is a cornerstone for understanding solid-state phase transformations, including crystallization.
• However, the standard KJMA theory has limitations when applied to finite-size systems, such as thin films.
• These limitations necessitate the development of new models that account for finite dimensions.

Purpose of the Study:

• To develop a novel mathematical model for the crystallization process in thin films.
• To overcome the limitations of the Kolmogorov-Johnson-Mehl-Avrami theory in finite-size systems.
• To analyze the impact of nucleation sites (boundaries and bulk) on crystallization kinetics.

Main Methods:

• Development of a mathematical model specifically for thin film crystallization.
• Incorporation of two distinct nucleation mechanisms: boundary nucleation and bulk nucleation.
• Derivation of a solution in terms of crystallization probability.

Main Results:

• The model successfully addresses the limitations of the KJMA theory for finite-size systems.
• A key finding is the non-uniform distribution of crystalline fraction within the thin film.
• Crystallization probability is used as a central metric to describe the process.

Conclusions:

• The proposed mathematical model provides a more accurate description of crystallization in finite-size thin films.
• Non-uniform crystalline fraction distribution is an inherent characteristic of crystallization in confined geometries.
• The model offers insights into controlling and predicting crystallization behavior in thin film applications.