%0 Journal Article
%J Journal of Physics-Condensed Matter
%D 2011
%T Nucleation and growth of Ag islands on the (root 3 x root 3)R30 degrees phase of Ag on Si(111)
%A Belianinov, A.
%A Unal, B.
%A Ho, K. M.
%A Wang, C. Z.
%A Evans, J. W.
%A Tringides, M. C.
%A Thiel, P. A.
%K 3x root 3-ag
%K competing processes
%K controlling energies
%K epitaxial-growth
%K LOW-TEMPERATURES
%K restructuring process
%K root-3-ag surface
%K scanning-tunneling-microscopy
%K si(111)-root-3x-root-3-ag surface
%K small-cluster mobility
%M ISI:000291658700003
%P 265002
%R 10.1088/0953-8984/23/26/265002
%U ://000291658700003
%V 23
%X We use scanning tunneling microscopy to measure densities and characteristics of Ag islands that form on the (root 3 x root 3) R30 degrees-Ag phase on Si(111), as a function of deposition temperature. Nucleation theory predicts that the logarithm of island density varies linearly with inverse deposition temperature. The data show two linear regimes. At 50-125 K, islands are relatively small, and island density decreases only slightly with increasing temperature. At 180-250 K, islands are larger and polycrystalline, and island density decreases strongly with increasing temperature. At 300 K, Ag atoms can travel for distances of the order of 1 mu m. Assuming that Ag diffusion occurs via thermally activated motion of single atoms between adjacent sites, the data can be explained as follows. At 50-125 K, the island density does not follow conventional Arrhenius scaling due to limited mobility and a consequent breakdown of the steady-state condition for the adatom density. At similar to 115-125 K, a transition to conventional Arrhenius scaling with critical nucleus size (i = 1) begins, and at 180-250 K, i > 1 prevails. The transition points indicate a diffusion barrier of 0.20-0.23 eV and a pairwise Ag-Ag bond strength of 0.14 eV. These energy values lead to an estimate of i approximate to 3-4 in the regime 180-250 K, where island density varies strongly with temperature.
%Z 777XOTimes Cited:0Cited References Count:50
%8 07/06
%@ 0953-8984