HOWE, C.J. ... et al, 2010. Ultra-thin films and surface alloying of Pd on Cu(1 1 1) investigated by medium energy ion scattering. Surface Science, 604 (2), pp. 201-209.
The structure of Pd films on Cu(1 1 1) and the alloying between the films and the substrate have been
investigated by medium energy ion scattering (MEIS) using 100 keV H+ ions. Data are presented for
the ½ 1 10 and ½ 1 1 4 alignments (nominal one- and three-layer alignments, respectively). It is found that
beyond 1 ML the Pd grows in a twinned fcc structure, the incommensurate nature of which increases the
visibility of the Cu(1 1 1) substrate to MEIS. Deposition of 0.2 ML of Pd produces a structure in which Pd
mostly occupies the top two layers which have interlayer distances d12 = 208 ± 4 pm and d23 =
211 ± 4 pm. Some twinning is also present in this structure. Upon annealing 1.6 ML of Pd to 600 K for
1 min, the copper and palladium interdiffuse leaving around 0.4 ML of visible palladium. Energy plots
show that there are several layers with an altered structure present over at least part of the surface. This
may be due to large scale interdiffusion or alloy island formation. Incremental annealing to successively
higher temperatures shows that the structural transformation begins around 500K.