Indium for Deep-Ultraviolet Surface-Enhanced Resonance Raman Scattering

The dielectric constant of indium in the deep-ultraviolet (DUV) region satisfies the conditions for localized surface plasmon resonance with low absorption loss. We report that indium acts as an agent of efficient surface-enhanced resonance Raman scattering (SERRS) in the DUV. Indium-coated SERRS substrates were prepared by depositing indium on fused silica glass substrates with control of the deposition thickness to tailor the plasmon resonance in the DUV. With excitation at 266 nm, SERRS was observed from thin adenine films deposited on the indium-coated substrates, and the signal intensity was up to 11 times higher than that of a bare fused silica glass substrate. FDTD calculations showed that an enhanced electromagnetic field can be locally generated on the indium-coated substrates. Considering the volume of the enhanced field region in the excitation spot, we estimated the average enhancement factor to be 102 or higher. Our results indicate that indium is a promising and easy-to-use metal for efficiently exciting DUV-SERRS of samples containing a small number of molecules.