Temperature-induced irreversible changes in the PdCu(110) surface microstructure

Abstract

PdCu(110)single crystal alloy surfaces were studied after sputtering and annealing up to temperatures at which enhanced Cu segregation and partial surface disordering significantly influenced the surface structure and its composition. Pd-rich, Cu-rich and surfaces with mixed PdCu compositions were examined. Surfaces were investigated using video low energy electron diffraction, Auger electron spectroscopy for the surface region of ∼ 4 layers depth and thermal desorption spectroscopy of CO for outer surface layer analysis. The atomic concentration 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, which is released by the surface microstructure containing only between 28% and 60% atoms in ordered domains. The domains were some 10–20 lattice cells large and were limited by grain boundaries. Domain sizes and the crystallinity were measured at 115K, after annealing the samples at temperatures above the preparation temperature. The irreversible temperature-induced growth of the surface domains was influenced by volume (segregation) and by surface processes (roughening, partial disordering) and proceeded with the equilibrium shape of domains.