Surface termination revealed by directional elastic peak electron spectroscopy

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In this work the results of investigations concerning the termination of the Ru(0001) surface are presented. All experiments were carried out with the use of a retarding field analyser. The cleanness of the sample was monitored by Auger electron spectroscopy. After the cleaning procedure the long range order of surface atoms was proved by the observation of sharp diffraction spots with the use of low energy electron diffraction. The short range order of atoms within the surface-near region was investigated with the use of directional elastic peak electron spectroscopy. The experimental intensity distributions presented as stereographic projections were recorded for different energies of the primary electron beam Ep. The six-fold symmetry intensity pattern observed in all intensity plots reflected the contribution of A and B terminated terraces of the Ru(0001) surface. The quantitative analysis of the experimental data, presented in the form of stereographic distributions and azimuthal profiles, and performed by means of contrast values of intensity maxima, showed the equal population of A and B terminated terraces. The data are discussed in the context of single and double steps on Ru(0001) and face centered cubic (111) samples, and the theoretical distribution for the A terminated Ru(0001) surface obtained with the use of the multiple scattering theory is presented.