Fabrication And Irradiation Induced Modifications Of Cu Nanoparticles Embedded In SiO₂

Owing to their peculiar properties, metal nanoparticles （NPs） have manypotential applications in various fields, such as opto-electronics, biosensor, opticalswitch, etc. High fluence ion implantation combined with thermal treatment indifferent atmospheres has been proved to be one of the most powerful techniques.However, the implants introduced by ion implantation usually exhibit Gaussiandistributions, which results in formation of NPs with size and spatial distribution in awide range due to inhomogeneous nucleation processes. Therefore, size control of theNPs together with the modulation of their physical properties is still of the greatchallenge for synthesis and practical aapications of NPs in substrate by means of ionimplantation. In this dissertation, using Cu ion implantation into SiO₂at high fluenceas well as the subsequent irradiation of N and Zn ions, the structure, optical propertiesof the fabricated NPs have been studied in detail by various techniques, includingglancing x-ray diffraction spectroscopy （GXRD）, cross-sectional transmissionelectron microscopy （XTEM）, ultra-violet visible spectrometer （UV-Vis）, andphotoluminescence （PL）. The investigation contents and achieved results are asfollow:（1） Cu NPs embedded into SiO₂were fabricated by implantation of45keV Cuions at a fluence of1×10¹⁷ions/cm², and were then irradiated at room temperature by190keV N ions at fluences of5×10¹⁵and1×10¹⁶ions/cm², respectively. Themodification of Cu NPs has been investigated after subsequent annealing in nitrogenambient at different temperatures. Our results clearly show that low fluence N ionirradiation together with600℃annealing could induce significant enhancement of theCu SPR signal with a reduction of full width at half maximum （FWHM） by tailoringthe distribution of Cu NPs, while no obvious change of the Cu SPR signal is found inhigh fluence irradiated samples. The SPR peak becomes very weak after800℃annealing. The results from Rutherford back-scattering spectroscopy measurementsgive the evidence that with the increasing annealing temperature, the distribution ofCu content for all samples becomes narrower in SiO₂matrix. The Cu atoms candiffuse at high annealing temperature. PL measurements give a strong and broadluminescent band of the Cu-related NPs, which is situated in a wavelength of500-600 nm.（2） SiO₂samples were sequentially implanted with45keV Cu and Zn ions at thesame fluence of110¹⁷/cm², and subjected furnace annealing in the temperature rangeof400-600oC for in nitrogen ambient. The fabrication, evolution and opticalproperties of nanoparticles have been studied in detail. Our results clearly demonstratethat Cu-Zn alloy NPs with bcc structure have been synthesized after500℃annealing,which present a stronger SPR peak at about515nm as well as a luminescent bandaround560nm. As annealing temperature increases to600℃, the Cu-Zn alloy hasbeen found to decompose, leaving a stronger SPR peak corresponding to the Cu SPR.Such SPR absorption is significantly larger than that found in Cu ion singly implantedSiO₂after annealing at the same conditions. Moreover, the size distribution andstructures of the synthesized Cu-Zn alloy NPs have been also studied by using XTEMobservations.