The growth of Fe nanoclusters on the Ge(001) and MoO2/Mo(110) surfaces has been studied using
low-temperature scanning tunneling microscopy (STM) and X-ray magnetic circular dichroism
(XMCD). STM results indicate that at low coverage Fe atoms self-assemble on both surfaces into
well-separated nanoclusters, which nucleate at equivalent surface sites. Their size, shape, and the
observed spatial separation are dictated by the substrate and depend on preparation conditions.
Annealing the Fe nanoclusters on Ge(001) at 420K leads to the formation of linear nanocluster
arrays, which follow the Ge dimer rows of the substrate, due to cluster mobility at such
temperature. In turn, linear Fe nanocluster arrays are formed on the MoO2/Mo(110) surface at
room temperature at a surface coverage greater than 0.5 monolayer. This is due to the more
pronounced row pattern of the MoO2/Mo(110) surface compared to Ge(001). These nanocluster
arrays follow the direction of the oxide rows of the strained MoO2/Mo(110) surface. The Fe
nanoclusters formed on both surfaces show a superparamagnetic behavior as measured by XMCD