The structure and growth of ultra-thin Au and Pd films on Cu(001) were studied by low-energy ion scattering and low-energy electron diffraction. Due to the existence of a kinetic pathway for intermixing, both Au and Pd were incorporated into the Cu(001) surface at room temperature, forming a c(2 x 2) surface alloy at a coverage of 0.5ML. At Au coverage near 1.2ML, the surface layer was pure Au; this was caused by Au-induced segregation from the underlying c(2 x 2) layer to the surface. No second- and/or third-layer Au was evident. In contrast to this, for the Pd/Cu(001) case a (2 x 2)p4g clock reconstruction was formed after deposition of 1ML Pd. The low-energy ion scattering data, through comparisons with 3-D computer simulation, reveal a 0.25Å lateral clockwise - anticlockwise displacement of the first-layer Pd atoms. A simple model for this clock reconstruction was proposed. The driving force behind the de-alloying for the Cu-Au alloy and Pd-induced reconstructing for the Cu-Pd surface was also considered.

Au-Segregated Dealloying and Pd-Induced Clock Reconstructing of Cu(001). Y.G.Shen, J.Yao, D.J.O'Connor, B.V.King, R.J.MacDonald: Journal of Physics - Condensed Matter, 1996, 8[27], 4903-18