Construction Of "Hotspots" In Patterned Composite Nanostructures And The Machnism For Enhancement

Surface-enhanced Raman Scattering(SERS) is a kind of high sensitive detection technique, in which the substrate of high SERS activity, stability and reproducibility is of great significance for SERS application and basic research. The ordered two-dimensional polystyrene(PS) colloidal array is used as the substrate for magnetron sputtering to build SiO2-Ag patterned composite nanostructure array, which suitable for high sensitivity of the application of SERS effect. The effects of the substrate configurations, the particle size, the gap density, and the surface morphology on the electromagnetic field distribution and plasma coupling. And the possible enhancement mechanism of SERS is discussed.First, planar composite SiO2-Ag substrate is fabricated by cosputtering Ag and SiO2 onto Si surface. The surface roughness of composite SiO2-Ag substrate is more than the planar Ag substrate. The configuration of the material is changed by co-sputtering to realize the controllable “hotspots” density and the performance of SERS active substrate is realized by changing the sputtering parameters.Second, SERS-active “Strawberry”-typed substrate is fabricated by cosputtering Ag and SiO2 onto PS templates of the different diameters. Each “Strawberry” is composed of 2-5 nm amorphous SiO2 and 10-20 nm Ag nanoparticle, which provides more “hotspots”. SiO2-Ag film shows the anisotropic growth and the longitudinal growth speed is greater than the lateral. With the increase of SiO2-Ag film thickness, the surface roughness of the film and the distance between the adjacent “Strawberry” are changed, which lead to the changed electromagnetic field coupling and the changed SERS enhancement ability. Different excitation wavelength of light is used to test SERS. The results show that of “Strawberry-typed” arrays show the high enhancement ability from the visible to near infrared light region. All samples surface has good stability and uniformity.Finally, the ordered patterned [Ag 30 nm/SiO2 5 nm]n(n=1-4) “Rod-Cap” multi-film arrays are fabricated by the combination of ordered template and magnetron sputtering technology. SEM shows the anisotropic growth of the multi-film. The surface morphology and the SERS enhancement performance are changed greatly when the [Ag/SiO2]n(n=4) “Rod-Cap” multi-film arrays are annealed at different temperatures. And the SERS enhancement is the largest after annealing at 600 oC. When the multi-film period increases, the SERS peaks are enhanced obviously. In addition, the layer of SiO2 not only improves SERS enhancement but also increases the stability of the SERS substrate.