Even though the capping layer had a thickness of only ~3 nm, it effectively protects the iron structure underneath from oxidation under ambient conditions, as confirmed by photoelectron microscopy. In this way, the lithographic fabrication of layered nanostructures has been realized, with significant potential for future applications.

More specifically, the EBID team from Erlangen can perform the EBID under well defined and clean conditions; that is, in an ultra high vacuum (UHV) environment. With this unique approach, the group was recently able to overcome existing limitations concerning the purity of EBID nanostructures and fabricated pure iron deposits from the precursor iron pentacarbonyl, Fe(CO)5.

Safeguarding the structure

In order to further characterize the electronic and magnetic properties of these iron nanostructures, they have to be removed from the UHV chamber, leading to oxidation of the iron and to changes in its physical properties. The newly established process enables the metallic iron nanostructure to be protected with a titanium oxide capping layer, grown with the precursor titanium isopropoxide (TTIP). The effectiveness of this 3 nm thick cap was verified using X-ray photoelectron microscopy at BESSY II in Berlin.

From a more general point of view, the stepwise application of two or more precursors in EBID opens up a novel pathway for tailoring the fabrication of nanostructures. For example, the assembly of functional multilayer components for use in nanoelectronic applications, which might consist of magnetic, conducting, semiconducting and/or insulating materials.

The researchers presented their work in the journal Nanotechnology.