The present study is focused on the development of advanced technology for creation of plasmonic composite nanostructures for Surface Enhanced Raman Spectroscopy (SERS) detection of ammonium nitrate. The investigation of the interaction of nanostructured composite objects with electromagnetic field, the description of their optical properties as well as determination of mechanisms and conditions for their effective modification brings the information for potential application as SERS substrates. The ZnO thin films are deposited by pulsed lased deposition (PLD) in an oxygen environment at high substrate temperature. The laser grown ZnO films are modified by Ag-ion implantation. The produced nanocomposites are subsequently laser annealed at different laser wavelengths. The influence of the ion implantation doses and the laser annealing parameters on the SERS activity of produced nanostructures is investigated. The observation of morphology of the samples demonstrates the influence of the laser annealing wavelength on the size distribution of embedded silver nanoparticles on the ZnO matrix. The plasmonic behaviour of embedded metal nanoparticles is determined by studying the optical properties of the fabricated structures. The proposed combined method for synthesis has potential application in fabrication of reliable substrates for Raman spectroscopy analysis with high sensitivity. The design of appropriate structures by laser and ion implantation methods can increase the efficiency of the high resolution analyses.
The present work concerns the fabrication and the investigation of Ag nanoparticles, surface embedded in the pulsed laser deposition (PLD) grown ZnO thin films. The third-harmonic Nd:YAG laser is used for PLD of ZnO thin films. The ion implantation technique for Ag doping in ZnO matrix is used. The morphology, texture and composition of the samples are investigated. The Ag distribution in the implanted near-surface region is investigated as a function of the processing conditions. The influence of the substrate temperature and ambient oxygen pressure during the PLD growth of ZnO films is studied. The applied processing parameters during the deposition of ZnO thin films lead to different microstructure of ZnO host matrix and have a significant impact on the properties of subsequently produced Ag/ZnO nanocomposites. The changes of optical surface plasmon resonance (SPR) band of synthesized Ag nanoparticles for different morphologies are analyzed for implanted samples. The composite nanostructures are found to exhibit SPR absorption properties of metal nanoparticles after the ion implantation, especially pronounced for the samples with laser grown ZnO matrix at high substrate temperatures. This study demonstrates how the different crystal structure of the ZnO supporting material, influences the Ag implantation process and, respectively, the properties of the produced Ag/ZnO nanocomposites.
Recent results on the interaction of high power laser pulses with dielectrics containing metal nanoparticles are observed. The excimer laser pulse modification of copper nanoparticles synthesized by ion implantation in silicate glass are considered. Pulsed laser irradiation makes it possible to modify such composite layer, improving the uniformity in the size distribution of the nanoparticles. Changes induced by pulsed laser exposure suggest there are both reductions in average size of the metal nanoparticles, and some long-range dissolution of metal atoms in the matrix. Experimental data on laser modification are explained by photofragmentation of the nanoparticles in the dielectric matrix.
The interaction of excimer laser pulses with silica consisting ion-synthesized copper nanoparticles is studied. Using
optical reflectance of composite layers it is established that at the initial stage laser annealing leads to the fragmentation
of the nanoparticles to smaller ones. After continuous irradiation by several pulses, the nanoparticles become larger due
to the heating of the surrounding glass. The laser treatment for a longer time (more than several tens pulses) results in
the dissociation of nanoparticles into small clusters and individual atoms. The mechanisms responsible for the
modification of the composite material under high power laser radiation are discussed.
Recent results on the interaction of high power laser pulses with various dielectric materials containing metal
nanoparticles are reviewed. The excimer laser pulse modification of silver nanoparticles synthesized by ion implantation
in soda-lime silicate glasses are considered. One of features of composite samples prepared by the low energy ion
implantation is the growth of metal particles with a wide size distribution in the thin depth from the irradiated substrate
surface. Pulsed laser irradiation makes it possible to modify such composite layer, improving the uniformity in the size
distribution of the nanoparticles. Changes induced by pulsed laser exposure suggest there are both reductions in average
size of the metal nanoparticles, and some long-range dissolution of metal atoms in the matrix. Experimental data on laser
modification are explained by melting of the nanoparticles in the dielectric matrix.
Recent results on synthesis of silver nanoparticles by ion implantation in various dielectrics are presented. Composites
demonstrate specific nonlinear-optical properties such as saturated and two-photon absorption in visible spectral area.
Excitation, focusing, and directing of surface plasmon polaritons (SPPs) with curved chains of bumps located
on a metal surface is investigated both experimentally and theoretically. We demonstrate that, by using a
relatively narrow laser beam (at normal incidence) interacting only with a portion of a curved stripe or chain
of nanoparticles, one can excite an SPP beam whose divergence and propagation direction are dictated by the
incident light spot size and its position along the structure. It is also found that the SPP focusing regime is
strongly influenced by the chain inter-particle distance. Extensive numerical simulations of the configuration
investigated experimentally are carried out for a wide set of system parameters by making use of the Green's
tensor formalism and dipole approximation. Comparison of numerical results with experimental data shows
good agreement with respect to the observed features in SPP focusing and directing, providing the guidelines
for a proper choice of the system parameters. It was found that the focusing regime of SPPs is strongly
influenced by the chain inter-bump distance, so that the focusing and directing effects with optimal properties
can be obtained only when the chain inter-bump distance is smaller than the SPP wavelength. Following the
experimental conditions, we have studied the role of the size of light spot exciting SPPs. Spectral dependence
of the focusing waist is also numerically studied for gold surface taking into account the ohmic loss.
Rapid advance of nanostructuring technologies offers new possibilities for flexible and low-cost fabrication of plasmonic
components and devices. In this contribution, we study applications of laser-based nonlinear lithography for the fabrication of dielectric surface-plasmon-polariton (SPP)-structures. These structures can be used for localization, guiding, and manipulation of SPPs on a subwavelength scale. Effective excitation of SPPs on dielectric structures and focusing of the generated SPPs are studied. The characterization of the SPP structures is performed by plasmon leakage radiation microscopy. Laser-based nonlinear lithography,
e.g. two-photon polymerization technique, allows the
fabrication of dielectric waveguides, splitters, and couplers directly on metal surfaces. The fabricated dielectric structures
on metal films are demonstrated to be very efficient for the excitation of SPPs. Using these structures, excitation,
focusing, and guiding will be demonstrated.
Renewed and growing interest in the field of surface plasmon polaritons (SPPs) comes from a rapid advance of
nanostructuring technologies. The desired nanostructures are usually fabricated by electron- or ion-beam lithography. An
alternative approach is the application of two-photon polymerization (2PP) or nonlinear lithography. Both these
technologies are based on nonlinear absorption of near-infrared femtosecond laser pulses. With 2PP, the fabrication of
three-dimensional micro-objects and photonic crystals with a resolution down to 100 nm is possible. In this contribution,
we study applications of advanced femtosecond laser technologies for the fabrication of SPP structures. We demonstrate
that resulting structures can be used for excitation, guiding, and manipulation of SPPs on a subwavelength scale.
Characterization of these structures is performed by detection of the plasmon leakage radiation (LR). 2PP allows the
fabrication of dielectric waveguides, splitters, and couplers directly on metal surfaces. The fabricated dielectric structures
are also very efficient for the excitation of SPPs. Using these structures, excitation and focusing of the resulting plasmon
field can be achieved.
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