Localized surface plasmon resonance of a Cu nanodot array covered with a native oxidation layer

Exploring the localized surface plasmon resonance (LSPR) of Cu nanostructures with native oxidation layers is very important for attaining plasmonic applications. A Cu nanodot array (NDA) was fabricated on an indium tin oxide substrate using an anodic aluminum-oxide layer with through-holes as a shadow mask. The surface chemical states and plasmonic properties of the Cu NDA and Cu film prepared for comparison were investigated via X-ray photoelectron spectroscopy (XPS) and ultraviolet‒visible spectroscopy. The XPS-depth profile indicated that the native oxide layer on the 50-nm-thick deposited Cu film was approximately 4.3 nm thick. For the Cu film, an absorption dip was observed at 573 nm, with two shoulder peaks attributed to the surface-oxide layer. The LSPR of the Cu NDA with a dot diameter of 60(± 5) nm was clearly observed at 652 nm despite the presence of a native oxide layer.