Properties of PdCu(110) single crystal alloy surfaces: reversible changes of domain sizes

Abstract

The composition of PdCu(110) single crystal alloy surfaces ( bulk Pd Cu = 1:1 ) can be changed by sputtering and annealing at different temperatures. A survey of surface structures and compositions in equilibrium shows the influence of Cu segregation. Samples with Cu Pd ratios in the surface region (≅ 4 layers) from 0.3 to 1.3 and with (1 × 2) and (1 × 1) surface structures were prepared. Surfaces with ~ 100% Pd atoms and mixed compositions of Pd and Cu atoms (down to ~ 70% Pd) at the top surface layer were investigated. Methods used for characterization were video low energy electron diffraction for structure analysis, Auger electron spectroscopy for the surface region of ~ 4 layers depth and CO thermal desorption spectroscopy for composition analysis of the top surface layer. Domain extents along [10] and [01] crystallographic directions, of surfaces with different compositions, changed reversibly when measured during sample heating and cooling cycles. The change proceeds in a manner that depends on the sizes of domains, on the crystalline amount and on the amount of Cu in the surface region. The surface domains contain a small number of lattice cells (~9 to ~18) and a large amount of atoms in the disordered intercrystalline areas.