TEMPERATURE-INDUCED IRREVERSIBLE CHANGES IN THE PDCU(110) SURFACE MICROSTRUCTURE

PdCu(110)single crystal alloy surfaces were studied after sputtering a nd annealing up to temperatures at which enhanced Cu segregation and p artial surface disordering significantly influenced the surface struct ure and its composition. Pd-rich, Cu-rich and surfaces with mixed Pd-C u compositions were examined. Surfaces were investigated using video l ow energy electron diffraction, Auger electron spectroscopy for the su rface region of similar to 4 layers depth and thermal desorption spect roscopy of CO for outer surface layer analysis. The atomic concentrati on ratio 1:1 in the matrix and the misfit in building the bcc lattice of Pd and Cu atoms could contribute to considerable surface stress, wh ich is released by the surface microstructure containing only between 28% and 60% atoms in ordered domains. The domains were some 10-20 latt ice cells large and were limited by grain boundaries. Domain sizes and the crystallinity were measured at 115 K, after annealing the samples at temperatures above the preparation temperature. The irreversible t emperature-induced growth of the surface domains was influenced by vol ume (segregation) and by surface processes (roughening, partial disord ering) and proceeded with the equilibrium shape of domains. (C) 1997 E lsevier Science Ltd. All rights reserved.