Formation and morphology of closed and porous films grown from grains seeded on substrates: Two-dimensional simulations

TL;DR

This study uses two-dimensional simulations to analyze the topological transitions, morphology, and critical behaviors of porous and closed films formed from grains on substrates, providing insights for manufacturing and theoretical understanding.

Contribution

Introduces new raster-free algorithms combining computational geometry and network theory to study film morphology and transitions in grain-seeded films.

Findings

Porous film morphology depends sensitively on initial grain surface fraction.

Pinholes exhibit critical survival behavior at film closure transition.

Morphological metrics vary significantly with initial conditions and film evolution.

Abstract

Two-dimensional simulations are used to explore topological transitions that occur during the formation of films grown from grains that are seeded on substrates. This is done for a relatively large range of the initial value $\Phi_s$ of the grain surface fraction $\Phi$. The morphology of porous films is captured at the transition when grains connect to form a one-component network using newly developed raster-free algorithms that combine computational geometry and network theory. Further insight on the morphology of porous films and their suspended counterparts is obtained by studying the pore surface fraction $\Phi_p$, the pore over grain ratio, the pore area distribution, and the contribution of pores of certain chosen areas to $\Phi_p$. Pinhole survival is evaluated at the transition when film closure occurs using survival function estimates. The morphology of closed films ($\Phi = 1$) is also characterized and is quantified by measuring grain areas and perimeters. The majority of investigated quantities are found to depend sensitively on $\Phi_s$ and the long-time persistence of pinholes exhibits critical behavior as a function of $\Phi_s$. In addition to providing guidelines for designing effective processes for manufacturing thin films and suspended porous films with tailored properties, this work may advance the understanding of continuum percolation theory.