Passivating Polycrystalline Copper with an Ultrathin Samarium Layer

Herein, it is reported that how a layer of samarium (Sm) with a thickness equivalent to approximate to 2 atoms (0.8 nm) deposited by thermal evaporation is remarkably effective at passivating polycrystalline copper (Cu) toward oxidation in ambient air. To monitor the rate of Cu oxidation in real time, slablike Cu films with a thickness of 9 nm are fabricated on glass modified with a layer of 3-mercaptopropyl silatrane, which immobilizes condensing Cu atoms by reaction with the thiol moiety, promoting slablike film formation at very low thickness. Upon exposure to ambient air the rate of increase in electrical resistance due to reaction with oxygen and water is slowed by more than an order of magnitude when the Cu film is capped with the ultrathin Sm layer. After 1 year, the resistance increases by approximate to 30% as compared to approximate to 190% for Cu films without an ultrathin Sm layer. Photoelectron spectroscopy, atomic force microscopy, and Kelvin probe measurements shed light on the underlying mechanism of passivation. Additionally, the ultrathin Sm layer is greatly lowering the work function of polycrystalline Cu films making this approach attractive for applications requiring a low-work-function electrode with high stability in air. An ultrathin layer of samarium (Sm) with a thickness equivalent to approximate to 2 monolayers is remarkably effective at passivating polycrystalline copper (Cu) films toward oxidation in ambient air. The ultrathin Sm layer lowers the work function of the Cu film down to approximate to 3.8 eV, making this approach attractive for applications requiring a low-work-function electrode with high stability in air.image (c) 2024 WILEY-VCH GmbH