Generation of clean iron structures by electron-beam-induced deposition and selective catalytic decomposition of iron pentacarbonyl on Rh(110).

We explore the electron-beam-induced deposition (EBID) of iron pentacarbonyl, Fe(CO)5, in ultrahigh vacuum (UHV) on clean and modified Rh(110) surfaces by scanning electron microscopy (SEM), scanning Auger microscopy (SAM), and local Auger electron spectroscopy (AES). In EBID a highly focused electron beam is used to locally decompose the iron pentacarbonyl precursor molecules with the goal to generate pure iron nanostructures. It is demonstrated that the selectivity of the process strongly depends on the surface properties. On a perfect, clean Rh(110) surface almost no selectivity is observed; i.e., deposition of Fe is found on irradiated and nonirradiated surface regions due to catalytic decomposition of the Fe(CO)5. However, on a structurally nonperfect Rh(110) surface and on a Ti-precovered Rh(110) surface high selectivity is found; i.e., Fe deposits are primarily formed in irradiated regions. The role of catalytic and autocatalytic growth of iron on clean Rh respective iron deposits is discussed. The purity of the Fe deposits was always very high (>88%). It is demonstrated that the deposited Fe structures can be selectively oxidized to iron oxide by exposure to oxygen. Furthermore, attempts to write Fe line deposits were also successful, and line diameters smaller than 25 nm could be achieved.