Thickness controlled sol-gel silica films for plasmonic bio-sensing devices

We report a simple method for depositing silica layers of controlled thickness on planar plasmonic structures.
Tetraethoxysilane (TEOS) was used as silica precursor. The control of the silica layer thickness was obtained by
optimizing the sol-gel method and dip-coating technique, in particular by properly tuning different parameters such as
pH, solvent concentration, and withdrawal speed. The resulting films were characterized via atomic force microscopy
(AFM), Fourier-transform (FT) spectroscopy, and spectroscopic ellipsometry (SE). Furthermore, by performing the
analysis of surface plasmon resonances before and after the coating of the nanostructures, it was observed that the
position of the resonance structures could be properly shifted by finely controlling the silica layer thickness. The effect of
silica coating was assessed also