Nanoscale investigation of Si nanoribbon growth on Ag(110)
Résumé
We present a nanoscale investigation by means of scanning tunneling microscopy of Si nanostructure growth on the anisotropic silver (110) surface, in the submonolayer range. Four types of Si nanostructures are studied statistically as a function of the substrate temperature in the range 300 K to 500 K: isolated single-and double nanoribbons, which differ only by a factor of two in their width, and their respective bi-dimensional counterparts in the self-assembly regime. Our observations highlight different growth regimes controlled by kinetics. Below 320 K, the Si adatoms diffuse along the easy [11 0] direction, forming essentially isolated single nanoribbons randomly distributed on the silver terraces. At higher temperatures, transverse diffusion along the [001] direction is activated and a competition between the growth of self-assembled single nanoribbons and isolated double nanoribbons is observed. Above 440 K, a transition from one-to two-dimensional double nanoribbon growth is evidenced. At 490 K, the Si deposition results in the formation of massively self-assembled double nanoribbons. Based on Arrhenius analyses, activation barriers are found to be (125 + 15) meV and (210 + 20) meV for the formation of isolated Si nanoribbons and self-assembled Si double nanoribbons, respectively. Our results allow for a better understanding of the kinetic limiting processes which determine the submonolayer morphology and illustrate the role played by the missing row reconstruction of the Ag(110) surface in the formation of extended Si nanoribbon arrays. 2
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