Optical Response from Metal/Dielectric Nanocomposite Thin Films Systems Modified by Heavy Ion Irradiation

摘要

Nanocomposite layers formed by gold particles embedded in a dielectric matrix (SiO_2) were deposited by a hybrid technique combining plasma enhanced chemical vapor deposition (PECVD) and pulsed-DC sputtering. Spectroscopic ellipsometry was used to extract parameters related to the microstructure such as particle size and gold content. An energetic ion beam (30 MeV copper ions) was used to deform the nanoparticles. A detailed spectrophotometric study showed a blue-shift of the surface plasmon resonance (SPR) position as a function of the irradiation dose. This effect was correlated to the particle deformation from a spherical shape to an elongated structure along the direction of the ion beam. We show that such process is reversible in a sense that subsequent annealing of ion beam irradiated particles red-shifts the SPR to the initial position.