Enhanced Saturation Coverages in Adsorption-Desorption Processes

Many experimental studies of protein deposition on solid surfaces involve alternating adsorption/desorption steps. In this paper, we investigate the effect of a desorption step (separating two adsorption steps) on the kinetics, the adsorbed-layer structure, and the saturation density. Our theoretical approach involves a density expansion of the pair distribution function and an application of an interpolation formula to estimate the saturation density as a function of the density at which the desorption process commences, ρ1, and the density of the depleted configuration, ρ2. The theory predicts an enhancement of the saturation density compared with that of a simple, uninterrupted RSA process and a maximum in the saturation density when ρ2 = 2 3ρ1. The theoretical results are in qualitative and in semi-quantitative agreement with the results of numerical simulations.