Cerium adatoms, deposited on a Ag(111) surface, are found by low-temperature scanning tunneling microscopy to self-assemble into large ordered hexagonal arrays covering macroscopically the entire surface. We show that the 32 A periodicity of the superlattice is caused by the interaction of surface-state electrons with Ce adatoms and that the large-scale formation of the superlattice is governed by a subtle balance between the sample temperature, the surface diffusion barrier, and the concentration-dependent adatom interaction potential.

We report on a joint experimental and theoretical study of the ordered structures of melamine molecules formed on the Au( 111)-( 22× 3) surface. Scanning tunneling microscopy (STM) images taken under UHV conditions reveal two distinct monolayers one of which has never been reported before on gold. We also find that one of the structures may serve as a transition region ("domain wall") between islands formed by the other arrangement. Using state-of-the-art density functional calculations in conjunction with a systematic gas-phase analysis based on considering all planar structures melamine molecules can form with each other, we propose atomistic models for both structures and the transition region.

International audienceThe self-assembly of the star-shaped 1,3,5-tris(4-iodophenyl)benzene molecule is investigated using scanning tunneling microscopy (STM) at the solid–liquid interface. This molecule forms dimers that self-assemble into two-dimensional porous halogen–halogen bonded nanoarchitectures on the graphite surface. STM shows that the structure of the porous organic network can be tailored using different solvents. Neighboring dimers are binded to each other through two iodine···iodine bonds in 1-phenyloctane, whereas 1-octanol solvent leads to the formation of I4 synthons connecting together four molecular dimers. Iodine bonds appear to be a promising alternative to hydrogen bonds to engineer new organic porous structures on surfaces

The competition between the on-surface synthesis of covalent nanoarchitectures and the self-assembly of star-shaped 1,3,5-Tris(4-iodophenyl)benzene molecules on Au(111) in vacuum is investigated using scanning tunneling microscopy above room temperature. The molecules form covalent polygonal nanoachitectures at the gold surface step edges and at the elbows of the gold reconstruction at low coverage. With coverage increasing two-dimensional halogen-bonded structures appear and grow on the surface terraces. Two different halogen-bonded nanoarchitectures are coexisting on the surface and hybrid covalent-halogen bonded structures are locally observed. At high coverage covalent nanoarchitectures are squeezed at the domain boundary of the halogen-bonded structures. The competitive growth between the covalent and halogen-bonded nanoarchitectures leads to formation of a two-layer film above one monolayer deposition. For this coverage, the covalent nanoarchitectures are propelled on top of the halogen-bonded first layer. These observations open up new opportunities for decoupling covalent nanoarchitectures from catalytically active and metal surfaces in vacuum.