Growth of iron on gold (7 8 8) vicinal surface: From nanodots to step flow

The growth morphology of iron on Au(7 8 8) has been investigated from 45 K to 430 K by use of variable temperature scanning tunneling microscopy. This system displays an ordered growth regime of a nanodots array from 70 K to 300 K (room temperature, RT). According to the temperature, the dots are found to grow on two different sites: below 250 K, they form rounded isolated islands above the steps where local traps act as nucleation centers; from 250 K to 300 K, they have the shape of platelets regularly disposed along the bottom of the step edges and located on face centered cubic area of the Au(7 8 8) surface reconstruction. Above RT, as a function of temperature, we find a progressive transition of the growth morphology, from ordered platelets to a step flow growth. A surface alloy formation induced by the high step density is the driving force of this growth mode transition.