The thermodynamics of monolayer films adsorbed on nonuniform substrates is analyzed in terms of arbitrary but well characterized substrate heterogeneity. It is shown that a combination of vapor-pressure isotherms of a two-phase film and high-resolution diffraction can yield the distribution functions of binding energy and of crystallite size. These distributions can be used as a basis for characterizing all films subject to similar adsorption forces. The effects of these distributions are discussed, with reference to single-phase regimes, phase boundaries of two-phase regions, triple-point melting, and second-order transitions. Several specific examples drawn from recent literature are discussed. A method is developed for unfolding ideal film behavior from measurements on well-characterized nonuniform substrates.

• Received 21 November 1980

DOI:https://doi.org/10.1103/PhysRevB.24.295