DEEP LAYER OSCILLATORY SEGREGATION AND RELAXATION OF SUBSTITUTIONALLYDISORDERED MOXRE1-X(100) SURFACES

The surface structure and stoichiometry of the substitutionally disord ered alloy MoxRe1-x(100) were determined by quantitative LEED I(E) ana lyses for bulk concentrations of x = 0.75, 0.85 and 0.95. Diffraction intensities were measured and analysed for electron energies up to 600 eV in order to also access values of the physical parameters of deepe r layers. An excellent theory-experiment agreement, together with a la rge data base for each bulk stoichiometry, allow the accurate detectio n of rather strong oscillatory interlayer relaxations. They extend unu sually deep into the bulk, i.e. down to the sixth layer. Additionally, a ''sandwich segregation'' with Mo termination of the surface and Re enrichment in the second layer is found, which is held responsible for the deeper interlayer relaxations. (C) 1997 Elsevier Science B.V.