Evolution of a Steady State Island Size Distribution during Self-Assembled Monolayer Dissolution

Abstract

We have observed the dissolution of a self-assembled monolayer of octadecylphosphonic acid from a mica surface in real time using atomic force microscopy. Holes in the monolayer are observed to nucleate and grow with time, eventually percolating across the sample. The rate of dissolution is increased by flowing solvent through the cell compared to stagnant solvent. If the monolayer is brought into contact with a small enough volume of stagnant solvent, the surface coverage stabilizes at some point due to the buildup of adsorbate molecules in solution. Under these conditions of steady state surface coverage, the local dynamical processes of island shrinkage, growth, and nucleation continue, eventually leading to a distinctive island size distribution characteristic of the system. The final distribution is in good agreement with a decaying exponential form, consistent with a “point island” model of island shrinkage and growth.