Effects of native oxidation on Ti/TiO2 nanodot arrays and their plasmonic properties compared to Au nanodot arrays

Abstract Unlike for noble metals, localized surface plasmon resonance (LSPR) of metallic nanodot array (NDA), which forms a surface oxide layer, has not been fully explored. We have investigated the surface oxide layers, LSPR, and surface-enhanced Raman scattering (SERS) of Au and Ti/TiO2 NDAs with similar shapes. Au NDA and Ti/TiO2 NDA with 80 ± 5 nm diameters were fabricated on indium tin oxide glass substrates using anodic aluminum oxide masks. The native oxide surface layer of Au NDA was very thin, whereas the Ti/TiO2 NDA’s surface was identified as TiO2 due to its inherent oxide layer. XPS depth profiling confirmed that the Ti metal’s surface transformed into a native oxide layer of TiO2 on Ti metal. The SERS signal of the Au NDA was approximately 104 times higher than that of the Ti/TiO2 NDA. The Au NDA’s LSPR had a strong peak centered at 659 nm, while the Ti/TiO2 NDA’s LSPR had a broad peak centered at ~420 nm. The Ti/TiO2 NDA’s LSPR was weak because the native surface layer dampened the LSPR but was clearly observed in the visible light region. These results suggested that Ti/TiO2 NDA has the potential for use as a visible light-responsive photocatalyst in solar energy systems.