| Recently, metal nanoparticles(NPs) embedded in dielectric medium with novel linear and nonlinear optical properties have been frequently applied in many prospective applications, such as optical sensors, biomedicine, and all-optical switching devices. The study of fabrication and optical properties of metal NPs has become a hot research in nanotechnology. Among different methods to fabricate NPs, ion implantation has been proved to be suitable owing to its unique advantages. In this paper, amorphous SiO2 samples were sequentially implanted with Ti(Al) and Cu ions, and then subjected to thermal annealing at different temperatures. The modifications in structures and optical properties of the Cu NPs by prior Ti or Al ion implantation have been focused on. The main contents and results are given as follows.(1) Amorphous SiO2 samples were pre-implanted with 105 keV Ti ions at two different fluences of 1×1016 and 5×1016 cm-2, respectively, and then were subjected to implantation of 100 keV Cu ions at the fluence of 5×1016 cm-2. For comparison, samples singly implanted with Cu ions at the same conditions were also prepared. Accompanied with thermal annealing in a nitrogen atmosphere, the structures and optical properties of fabricated NPs at the effect of pre-implanted Ti ions were characterized in detail. The results show that the dual-implanted samples followed by 700 or 800 oC annealing display significantly enhanced surface plasma resonance(SPR) absorption bands compared to that of the Cu singly implanted sample at the same annealing condition. Besides, the SPR signals of the dual-implanted samples exhibit an increased intensity and redshift with increasing Ti fluence. Furthermore, by comparison with those in the Cu singly implanted sample, the nonlinear optical properties of the dual-implanted samples have obviously changed owing to the prior implantation of Ti ions.(2) As for the sample sequentially implanted with Ti and Cu ions at the same fluence of 5×1016 cm-2 followed by 800 °C annealing, the formation of core–shell NPs have been detected by cross-sectional transmission electron microscopy(XTEM) and energy dispersive X-ray spectroscopy(EDXS) etc. The cores of the NPs can be mainly from Cu atoms, whereas the shells could be made up of Ti or Ti-related compounds. The synthesized core–shell NPs exhibit significantly enhanced SPR absorption and improved third-order nonlinear susceptibility as compared with those in the Cu singly implanted sample.(3) Amorphous SiO2 samples were pre-implanted with 60 keV Al ions at two different fluences of 1×1016 and 5×1016 cm-2, respectively, and then were subjected to implantation of 100 keV Cu ions at a fluence of 5×1016 cm-2. For comparison, samples singly implanted with Cu ions at the same conditions were also prepared. Accompanied with thermal annealing in a nitrogen atmosphere, the optical properties of fabricated NPs at the effect of pre-implanted Al ions were also characterized in detail. The results show that the dual-implanted sample with pre-implanted Al ions at lower fluence displays enhanced SPR absorption and increased third-order nonlinear susceptibility compared to that in the Cu singly implanted sample after 800 °C annealing. However, the SPR absorption of Cu NPs was not enhanced by pre-implanted Al ions at higher fluence of 5×1016 cm-2. |
