Microscopic model of diffusion limited aggregation and electrodeposition in the presence of levelling molecules

TL;DR

This paper presents a cellular automata model for electrochemical deposition, showing how levelling molecules can transform dendritic, fractal deposits into dense, uniform layers by unbinding atoms, mimicking real leveller effects.

Contribution

A microscopic cellular automata model demonstrating how unbinding molecules influence deposit morphology, transforming fractal growth into dense layers in electrochemical processes.

Findings

Unbinding molecules lead to 100% dense deposits in 3D.

Field application suppresses fractal growth, increasing density.

Levelling molecules effectively prevent atom trapping during deposition.

Abstract

A microscopic model of the effect of unbinding in diffusion limited aggregation based on a cellular automata approach is presented. The geometry resembles electrochemical deposition - ``ions'' diffuse at random from the top of a container until encountering a cluster in contact with the bottom, to which they stick. The model exhibits dendritic (fractal) growth in the diffusion limited case. The addition of a field eliminates the fractal nature but the density remains low. The addition of molecules which unbind atoms from the aggregate transforms the deposit to a 100% dense one (in 3D). The molecules are remarkably adept at avoiding being trapped. This mimics the effect of so-called ``leveller'' molecules which are used in electrochemical deposition.