Self-Assembled Monolayers Impact Cobalt Interfacial Structure in Nanoelectronic Junctions

Controlling and understanding the interface formation between organic molecular layers and ferromagnetic materials is a crucial aspect in the implementation of organic spintronics. Here, the formation of thiol-containing molecular monolayers on template-stripped cobalt and oxidized cobalt surfaces is achieved. The successful attachment and quality of the aliphatic molecular structure and cobalt surface was followed with X-ray spectroscopic measurements. The self-assembly of octadecanethiol (ODT) and mercaptohexadecanoic acid (MHA) are contrasted, finding the self-assembly of the bifunctional molecule profoundly different than the thiol-alone species. In particular, the MHA-cobalt surface exhibits a very different interface following self-assembly the MHA species. Two different models of the interface formation are proposed based on the results. The data suggest the MHA/ethanol removes the cobalt oxide during the self-assembly as the prevailing model. The impact of this Co/molecule interface on electron transport through Co/molecule/Si molecular junctions is also discussed. These results provide insight into ex situ modification and functionalization of ferromagnetic interfaces impacting an important aspect of spin-based devices.