Spin-Polarized Electron Transfers in Organic/Inorganic Hybrid (Rectifying) Junctions

We formed a heterojunction based on a monolayer of nickel phthalocyanine (NiPc) and another layer of cobalt-doped ZnO (Co@ZnO) nanoparticles on an electrode. By tunneling current through a monolayer of the components that in turn yielded density of states (DOS) of the semiconductors, we located energy levels of NiPc, which were electron donating in nature, and also the band edges of the n-type nanoparticles. Energies of the components in a heterojunction showed that there would be a preferential transfer of electrons from Co@ZnO to NiPc in junctions formed in either sequence (NiPc|Co@ZnO and Co@ZnO|NiPc). We then proceeded to form heterojunctions with the magnetization vector of Co@ZnO and the easy magnetization axis of the metalorganic parallel to each other. When such aligned junctions were characterized with spin-polarized scanning tunneling spectroscopy (SP-STS), we observed that the configuration acted as a unique diode applicable to spin-polarized electrons.