Creation of an Atomic Superlattice by Immersing Metallic Adatoms in a Two-Dimensional Electron Sea

Abstract

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.

Self-organization of Ce adatoms onAg(111): A kinetic Monte Carlo study

“…Our simulations follow closely the experimental conditions of Silly et al 13,14 The two important questions have to be answered: ͑i͒ at which coverage the superlattice is formed and ͑ii͒ is the superlattice stable? Simulations have been performed for the concentration range between 0.2-2.0 %.…”

“…A difference in binding energy for Ce at these two sites cannot be seen in the experiment. 13,14 Therefore, fcc and hcp sites are considered in our simulations to be identical.…”

“…We set v 0 to 10 12 s −1 for the Ag surface. 13,14 The influence of the LRI on adatom diffusion is included in the hopping barrier which takes the form 16 …”

“…10 The breakthrough came with experiments of Silly et al on Ce adatoms on Ag͑111͒. 13,14 It has been discovered that the Ce atoms form well ordered hexagonal superlattice with a lattice constant of 32 Å. The Ce superlattice is most nicely ordered at 3.9 K. The LRI between Ce adatoms has been proposed to be the driving force for the self-organization of Ce adatoms.…”

Patterns of Organics on Substrates with Metallic Surface States: Why?, So??

“…6(c, d) contains plots of the probability of CO occupation for each of the 186 Cu substrate atoms exposed in the pore. While somewhat reminiscent of states in quantum corals, these plots differ qualitatively in their 3-fold rather than ring ("quantum onion") symmetry, as well as the much smaller area than inside a corral [13,55,56]. Calculations using KKR-GF methods [54][55][56] could impressively account for the standing wave patterns in corrals.…”