Item

Abstract

The PdCu(110) alloy single crystal surfaces, with atomic concentration ratio Cu:Pd = 1:1 in the bulk, were prepared with various compositions. Cu/Pd ratios in the surface regions, measured ≈ 4 layers deep, ranged from 0.3 to 2. Different compositions of the top surface layers were obtained, from exclusively Pd atoms, over mixtures of Pd and Cu atoms, to exclusively Cu atoms. The behaviour of video LEED spot intensities and profiles during sample heating and cooling was measured.

The PdCu(110) surface consists of domains containing ≈ 10–20 lattice cells depending on preparation procedure. The surface microstructure influences the temperature-induced processes at the surface: surface roughening and partial surface disordering, starting at ≈ 550 K and ≈ 700 K, respectively. The domain grain boundaries play an important role in the surface roughening process. At higher temperatures the domain size distribution, aside from grain boundaries, causes partial surface disordering. The two Cu segregation processes, starting at ≈ 550 K and at ≈ 700 K, are the volume counterparts to these surface processes.