Structure and growth in metal epitaxy on low-index Au surfaces—a comparison between solid∣electrolyte and solid∣vacuum interfaces

Low-temperature nucleation and growth of Zn on Au(111) and thermal stability toward (surface) alloy formation

As part of an extensive study of the interaction between Zn and Au in Zn/Au(111) model systems, we have systematically investigated the low-temperature (LT) nucleation and growth behavior of Zn on the Au(111) surface as well as the thermal stability of the resulting structures toward sintering, intermixing, and dissolution by scanning tunneling microscopy (STM) and x-ray photoelectron spectroscopy (XPS). Zn deposition at LT, at 105 K (STM) or 80 K (XPS), leads to nucleation and two-dimensional growth of Zn islands mainly at the elbows of the Au(111) herringbone reconstruction, with a slight preference for island formation at pinched-in (pi) rather than bulged-out (bu) elbows. Local surface intermixing during LT Zn deposition leads to local perturbations of the Au(111) herringbone reconstruction, which results in the formation of additional nucleation sites (edge sites). At higher coverages (>0.11 ML), island coalescence sets in. Testing the thermal stability by annealing experiments, we find the structures to be stable up to about 200 K, while at higher temperatures, 2D sintering, intermixing, and dissolution set in, with subtle differences between pi- and bu-elbow islands. This indicates largely comparable activation barriers for the underlying (surface-)diffusion and exchange processes. Upon annealing to 330 K, all island structures dissolved. Compared with previous reports on the growth of other metals on Au(111), Zn shows a rather high tendency for intermixing and can be considered to be typical of metal deposition systems with comparable barriers for 2D Zn detachment/sintering and intermixing/bulk diffusion.

Self-assembly of paired nanoribbons

Self-assembly of surface phase domains is a promising route to fabricate stable nanometer-scale structures. This Letter reports a novel labyrinth structure of orthogonal nanoscale ribbons of Cu4Pb3 ordered-alloy on Cu(100) formed by electrochemical deposition. The labyrinth develops as loops of Cu4Pb3 ribbons elongate as closely spaced paired stripes. The structure is explained in terms of elastic interactions between anisotropic surface stress domains, wherein stripes of different phase variants form attractive dipoles. An energetic analysis determines the physical conditions necessary for the structure to form.

Anion adsorption induced reversal of coherency strain

Experimental results are presented for stress evolution, in vacuum and electrolyte, for the first monolayer of Cu on Au(111). In electrolyte the monolayer is pseudomorphic and the stress-thickness change is -0.60 N/m, while conventional epitaxy theory predicts a value of +7.76 N/m. In vacuum, the monolayer is incoherent with the underlying gold. Using a combination of first-principles based calculations and molecular dynamic simulations we analyzed these results and demonstrate that in electrolyte, overlayer coherency is maintained owing to anion adsorption.