Fe Nanoclusters on the Ge(001) Surface Studied by Scanning Tunneling Microscopy, Density Functional Theory Calculations and X-Ray Magnetic Circular Dichroism.

The growth of Fe nanoclusters on the Ge(001) surface has been studied using low-temperature scanning tunnelling microscopy (STM) and density functional theory (DFT) calculations. STM results indicate that Fe nucleates on the Ge(001) surface, forming well-ordered nanoclusters of uniform size. Depending on the preparation conditions, two types of nanoclusters were observed having either four or sixteen Fe atoms within a nanocluster. The results were confirmed by DFT calculations. Annealing the nanoclusters at 420 K leads to the formation of nanorow structures, due to cluster mobility at such temperature. The Fe nanoclusters and nanorow structures formed on the Ge(001) surface show a superparamagnetic behaviour as measured by X-ray magnetic circular dichroism. 1