Nano-structuration of CoO film by misfit dislocations

We have studied the nano-patterning of CoO film induced by misfit dislocation network at the interface with the Ag(001) substrate.Grazing incidence diffraction (GIXD), X-ray photoemission spectroscopy (XPS) and low energy electron diffraction (LEED) have beenused to characterize chemistry and structure of the CoO layers. The XPS spectrum of the Co 2p core level permitted to establish thestoichiometric growth of CoO. The structure of the CoO film together with the absorption sites of cobalt and oxygen atoms was determined,thanks to GIXD measurements. Moreover we have followed the evolution of the in-plane lattice constant of the CoO as a functionof the film thickness. It turns out that the CoO film growth starts with the same in-plane lattice constant of the Ag(001) substrate upto 3–4 ML; afterwards the in-plane parameter of CoO steadily increases before reaching a stable value of 2.98 A ˚ at 23 ML. During therelaxation process, at about 8 ML of film thickness, we observe the formation of a buried misfit dislocation network. These dislocations,that have a period of 9.2 nm for a film thickness of 23 ML, induce mosaicity in the CoO film which then appears as a regular distributionof tilted domains._ 2006 Elsevier B.V. All rights reserved.