Substrate compatibility of Cryo-FIBID processes with the Co2(CO)8 precursor

Cryo-FIBID (focused ion beam induced deposition at cryogenic conditions) is an advanced nanofabrication technique that enables the controlled deposition of materials with high spatial resolution by condensing a precursor on a cooled substrate before ion beam irradiation. In this study, Cryo-FIBID using a Ga+ source and the Co2(CO)8 precursor was used to deposit cobalt layers on a variety of substrates, including metals, semiconductors, insulators, and graphene, without the need for conductive coatings on insulating surfaces. The microstructural and compositional properties of the deposits were probed by means of several microscopy techniques, which indicate that the deposits consist of homogeneous and compact cobalt-based thin layers. The investigation has revealed that two deposition parameters, the initial thickness of the condensed precursor layer and the Ga+ irradiation fluence, have a significant impact on the composition, microstructure and thickness of the final deposit. Interestingly, it was found that the cobalt content in the grown deposits depends strongly on the substrate material. Whereas deposits with a high cobalt content ( ~ 60 at.%) are produced on Si, Au and Al substrates, the use of SiO2, graphene and SrTiO3 substrates gives rise to deposits with a lower cobalt content ( ~ 40 at.%). The set of results highlights the versatility of Cryo-FIBID toward the growth of patterned cobalt-based structures on a wide range of substrates.