Electronic excitations and optical response of metal nanocomposites under heavy ion implantation

The optical transmission and ion-induced luminescence under implantation of copper ions into quartz glass (a-SiO₂) have been measured to study the processes of formation of copper nanoparticles. It is shown that in situ measurements are more informative in comparison with the ordinary approach—investigation of the properties of ion-implanted nanocomposites only after implantation. A series of experiments was performed to prove that the ion-induced luminescence band at 545–550 nm is due to Cu⁺ ions dissolved in a-SiO₂. The combined use of in situ optical techniques makes it possible to monitor the states of implanted copper (metal nanoparticles and dissolved atoms) by the change in the optical absorption near the surface plasmon resonance of nanoparticles and by the intensity of ion-induced luminescence of Cu⁺ states in solid solution. It is shown that the optical bands of defects, dissolved copper, and nanoparticles can be separated within a simple linear approximation. Near the surface plasmon resonance and defect bands, ion-induced transient optical absorption has been revealed. The transient optical absorption near the surface plasmon resonance is explained by the temperature effect. The relationship between the electronic excitation, radiation-induced optical response, and the kinetics of nanoparticle formation is analyzed. Several stages of nanoparticle formation have been established: accumulation of implanted copper in solid solution, nucleation of nanoparticles, coalescence, growth of nanoparticles, and saturation of nanocomposites.