| AVS 55th International Symposium & Exhibition | |
| Surface Science | Wednesday Sessions |
| Session SS1+NC-WeM |
| Session: | Surface Structure and Morphology |
| Presenter: | F. Stavale, Nat'l Inst. of Metrology & Federal U. of Rio de Janeiro, Brazil |
| Authors: | F. Stavale, Nat'l Inst. of Metrology & Federal U. of Rio de Janeiro, Brazil M.M. de Araújo, Nat'l Inst. of Metrology, Brazil A.A. Leitão, Nat'l Inst. of Metrology & Federal U. of Juiz de Fora, Brazil R.B. Capaz, Nat'l Inst. of Metrology & Federal U. of Rio de Janeiro, Brazil H. Niehus, Nat'l Inst. of Metrology & Humboldt-U. zu Berlin, Germany C.A. Achete, Nat'l Inst. of Metrology & Federal U. of Rio de Janeiro, Brazil |
| Correspondent: | Click to Email |
The development of superlattices of nanodots and nanomagnetism, metals on Si substrates are of great scientific and technological importance. Consequently metal deposition on Si(111) 7x7 has been studied intensively by the surface science community. The surface diffusion energies and diffusion pathways of the adsorbates are important subjects to understand the growth mechanism of nanostructures. In this sense the scanning tunneling microscopy (STM) appeared to be a powerful technique for the study of adatom diffusion on the Si(111) 7x7 surface. In general the transition metals expose a high reactivity usually due to the formation of silicide nanostructures. Although several reports on V-Si(111)-7x7 surface system are already available a detailed and complete study of the vanadium from the very beginning adsorption stages up to high coverage cluster and island coalescence on the Si(111)-7x7 substrate has not been yet performed. In this work, we report about an investigation from the low-coverage regime up to few monolayers of vanadium deposition on Si(111)-7x7 in the range of 100K up to 850K substrate temperature. A combination of STM, density-functional theory (DFT) adsorption energy calculations and simulated STM images has been applied. In the low coverage and temperature regime we identify the most common STM signatures in this system to be: (1) substitutional vanadium atoms at silicon adatom positions and (2) interstitial vanadium atoms between silicon adatoms and rest atoms. At higher temperatures the diffusion of adatoms and clusters promote cluster coalescence into specifically shaped nanoclusters which occupy very special unit cell positions of the substrate. Such clusters are composed by vanadium and silicon atoms into an initial silicide formation. Finally, at high coverage, depending on the initial vanadium coverage and the post-annealing temperature well shaped (faceted) VSi2 clusters are formed. In conclusion a model for the adsorption, diffusion and reaction of vanadium on the Si(111)-7x7 surface is proposed.