Optical Properties and Biosensor Application of Ultrathin Silver Films Prepared by Oblique Angle Deposition

Abstract

The optical properties of thin silver films fabricated by the oblique angle deposition method are investigated. The localized surface plasmon resonance (LSPR) wavelength can be easily tuned from 401 to 666 nm in the visible range by changing the film thickness from 5 to 100 nm and the deposition angle from 0 to 85°. Atomic force microscope images reveal that the LSPR peak position and the shape of the absorption spectra are associated with the nanoparticle size and distribution. The nanoparticles deposited at higher deposition angles are elongated and more uniform, and their polarized absorption spectra are shifted by changing the polarization of the incident light. The ability of the silver nanoparticle film to be a biosensor was explored by studying the stability of the silver film under liquid environment and by demonstrating the capability of detecting 10−10 M NeutrAvidin. The easy fabrication and fine LSPR tunability give the thin silver films great potentials in optical and biological applications.