Dynamical theory of low-energy-electron diffraction from disordered overlayers. II. Application to one-dimensional adsorbates

Results are presented of calculations of the elastic-scattering intensities of low-energy electrons from one-dimensional thermally disordered overlayers adsorbed on a two-dimensional rigid periodic substrate. The calculations are performed for isotropic scatterers and are based on the dynamical theory constructed in the preceding paper. A lattice-gas model is used to describe the thermodynamic properties of a half-monolayer coverage of the adsorb ate. The calculations exhibit three characteristic results predicted by such a model. First, the effective field of the overlayer exhibits a temperature behavior associated with the development of short-range order among the adatoms. Second, multiple scattering within all one-dimensional dynamical models is weak. Third, the angular profiles exhibit intensity minima whose angular position varies with incident-beam energy. This new effect is of purely dynamical origin, is independent of temperature, and is caused by interference between the scattering from the overlayer and that from substrate. Its occurrence renders inadequate single-scattering ("kinematical") models of beam broadening and beam splitting.