Thermal Annealing of Ag Implanted Silicon: Relationship between Structural and Optical Properties

Low energy Ag ions were implanted into silicon and annealed at different temperatures in order to generate plasmonic active silicon hybrids. It was found that as the ion fluence of irradiation was increased, a monotonic decrease in the absorption spectra in the ultraviolet region occurs, due to amorphization and macrostructuring of the Si surface. At the same time, the optical spectra are characterized by a strong band after implantation presenting the contribution of the surface plasmon resonance (SPR) of Ag nanoparticles. After heat treatment at 500 and 600 degrees C, the SPR peak shifts to lower wavelengths, as compared to as implanted samples, whereas the plasmon position shifts to higher wavelengths for annealing at 700 degrees C. This observation can be explained by either an out-diffusion of Ag or by stress relaxation and recrystallization of silicon.