Fractal growth of LiF on Ag(111) studied by low-temperature STM

We studied the fractal growth of LiF on Ag(111) at 77 K using low-temperature scanning tunneling microscopy. The observed island density as a function of the flux and the island density distribution reveal consistency with nucleation theory for the critical cluster size corresponding to i=1. The migration barrier for LiF monomers was estimated to be of the order of several tens of meV. The ramified (100)-oriented LiF aggregates exhibit a fractal dimension of d=1.75±0.01. No shape transition to dendritic growth was observed for fluxes ranging from F=2.4×10−2 to F=2.0×10−5 ML s−1 which is attributed to the different symmetries of adsorbate and substrate.