Quantitative determination of Cu(117) multilayer surface relaxations by LEED - art. no.155407

The relaxation of the first seven atomic layers of Cu(117) was determined b y quantitative low-energy electron diffraction (LEED). Intensity versus ene rgy spectra, I(E), were measured for the primary beam at near-normal incide nce to the (001) terraces. The data collected cover a cumulative energy ran ge of 3200 eV. Computation of I(E) spectra was performed in the angular mom entum representation by considering the surface as a single atomic slab. Fo r the variation of parameters, tensor LEED was applied. The experimental sp ectra are well reproduced over the entire energy range even for regions of low intensity. The first four layer spacings relax in a way to smooth the s urface corrugation, whereby the relative changes Deltad/d(0) amount (from t op) to -13%, -2.0%, -10%, and +7%. This leads to a reduction of the vertica l distance between step and corner atoms by 0.13 Angstrom. Comparison with experimental results for Cu(115) shows that this modification of the step s hape is rather independent of the terrace width. Comparison to theoretical results exhibits, however, some discrepancies with respect to both the expa nsion/contraction sequence and the amplitudes of the layer relaxations.