Surface Characterization by Adsorption Measurements: Competition between Heterogeneous Adsorption Potential and Adsorbate–Adsorbate Lateral Interactions

Le résumé fourni par la source

We address the problem of surface characterization via inversion of the adsorption isotherm equation for particles with repulsive nearest-neighbor interactions adsorbed on square lattices, combining theoretical analysis with Monte Carlo simulations. At low temperature (or strong lateral interaction), adsorption isotherms display a pronounced plateau at coverage θ = 0.5, separating two regimes. From θ = 0 to 0.5, adsorption occurs on isolated sites until a c (2 × 2) structure forms, with no particle–particle interaction. From θ = 0.5 to 1.0, adsorption fills the vacant sites of this structure, each new particle interacting with four neighbors. The isotherms for different coupling strengths w are well described by a two-local-isotherm model, with adsorption energies ϵ S and ϵ D corresponding to the two regimes. Thus, repulsive adsorption on a homogeneous surface can be mapped onto noninteracting adsorption on a heterogeneous bivariate surface, with ϵ S – ϵ D ∝ w . This duality highlights an intrinsic ambiguity in surface characterization based only on isotherms. We show that additional measurements, such as adsorption heats or fluctuation-sensitive observables, resolve this ambiguity. These thermodynamic arguments are reinforced by information-theoretic tools, providing insights into accurate surface topography characterization.

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