Stress induced surface structures and reactivity of thin layer Pd/Cu(1 1 0) deposits

Thin palladium layers deposited onto Cu(1 1 0) at coverage amounts varying from 0.1 to 6 ML have been studied using the scanning tunnelling microscope. Annealing the deposits at low temperature leads to surface structuring processes that are driven by the lattice mismatch stress energy: In a first step palladium and copper alloy to grow 2D terraces, next near to 1 ML coverage 3D islands form, then at 1.5–3 ML coverage a small amplitude undulation, running in the [1 −1 0] direction, develops on the top surface of islands. These surface morphologies have been discussed in regards to the very specific catalytic properties exhibited by the Pd/Cu(1 1 0) deposits. We propose in particular to correlate the remarkable increase in catalytic activity that was obtained from 2 to 3 ML Pd/Cu(1 1 0) deposits to specific surface sites created when the formerly (1 1 0) surface undulates in response to lattice stress.