Ultra-thin films and surface alloying of Pd on Cu(111) investigated by medium energy ion scattering

作者：Howe C J; Cropper M D^*; Fleming T P; Wardle R M; Bailey P; Noakes T C Q

来源：Surface Science, 2010, 604(2): 201-209.

DOI：10.1016/j.susc.2009.11.007

• Medium energy ion scattering
• Palladium
• Copper
• Surface alloy
• Ultra-thin film

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 [(1) over bar (1) over bar 0] and [(1) over bar (1) over bar (4) over bar] 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 d(12) = 208 +/- 4 pm and d(23) = 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 500 K.

• 出版日期2010-1-15