Dynamics of a registered monolayer adsorbed on a corrugated substrate: Two-dimensional surface-wave dynamics

Abstract

The dispersion curve of the vibrational modes of a registered monolayer adsorbed on a substrate exhibiting different adsorption sites are determined within the framework of a two-dimensional dynamical model for the total system. Phonon hybridization between the quasiacoustical and optical branches of the adlayer and the substrate modes leads to subtle avoided crossings of the dispersion curves. The monolayer vibrations perpendicular to the surface substrate exhibit a strong hybridization-induced splitting, not only with the Rayleigh substrate mode, but also with the transverse bulk mode of the solid. The anticrossing splitting near resonances is much slighter for the monolayer parallel vibrations and at small, but nonzero q values, for the quasiacoustical layer branch, and it occurs mainly with the longitudinal bulk mode. Dynamical parameters of the Ar monolayer adsorbed on MgO(100) substrate are used to illustrate the results.