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, $\rho_1$, and the density of the depleted configuration, $\rho_2$. 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 $\rho_2={2/3}\rho_1$. The theoretical results are in qualitative and in semi-quantitative agreement with the results of numerical simulations.