Periodic ZnO-Elevated Gold Dimer Nanostructures for Surface-Enhanced Raman Scattering Applications

摘要： The electron beam lithography-defined periodic ZnO-elevated gold dimer nanostructures for surface-enhanced Raman spectroscopy with strong electromagnetic field enhancements were fabricated in the present work. The ZnO nanorods (NRs) were grown on the patterned substrate using the hydrothermal process and Au dimers were deposited on the top surface of ZnO NRs, forming suspended gold dimers and providing plasmonic hot-spots with nanocavity effect. The effects of dimer radius, gap size and ZnO NR height on the dark-field scattering spectra and surface-enhanced Raman scattering (SERS) were investigated experimentally and theoretically. The SERS response was enhanced with increasing dimer radius and decreasing gap size. The SERS enhancement factor (EF) due to the localized surface plasmon resonance was calculated from simulation results. The calculated EF as a function of ZnO NR height showed the periodic trend of electric field intensity with the periodicity of about half of the exciting laser wavelength, and was in agreement with SERS measurements. Our hybrid substrates combining plasmonic nanocavity effect with charge transfer across the heterojunction denoted the potential candidate for SERS applications.