Further evaluation of the transform-deconvolution method for surface-structure determination by analysis of low-energy electron-diffraction intensities

Abstract

The conventional approach to surface structure determination by analysis of low-energy electron diffraction (LEED) consists of comparison between experimental intensities and intensities calculated on the basis of a model of the diffraction process and a trial model of the surface structure. Although this model calculation approach has been used with some success in the case of simple structures, it is unlikely that it can be easily extended to more complex systems unless a reasonable approximation to the structure is known or can be determined by another method. In this article we further describe and evaluate the transform-deconvolution method, which is in essence an adaption to LEED of the Patterson function method of x-ray crystallography, in which direct use is made of the experimental data without prior assumption of a model structure. Within the approximation of single-scattering theory it is shown that the Patterson functions of LEED intensities consist of sums of convolution products of structural and nonstructural terms from which the structural parameters can be recovered via a deconvolution process. Procedures are described for tackling the problem of nonuniqueness, which reslts from the limited amount of data available from a LEED experiment, and problems associated with the effects of multiple scattering. The results of application of the transform-deconvolution method to the analysis of LEED intensities from Cu(100), Ni(100), Al(111), and Al(100) are presented. Consistent values for the surface interlayer spacings are obtained from the analysis of a number of intensity spectra in each case.