Plasmonic Resonant Effect And Surface-enhanced Raman Scattering Properties Of Metal-dielectric Composite Systems

Surface-enhanced Raman scattering?SERS?technology has the advantages of ultra-high detection sensitivity,low detection limit,non-damage,rapid and efficient,and so on.It can also provide fingerprint information of molecular structure and has been widely used in many fields.Especially after the implementation of single-molecule detection by SERS technique,more and more researchers have begun to study SERS technique.However,the SERS substrate is the key to the SERS technology.The performance of the SERS substrate has a direct impact on the effect of SERS enhancement.The mechanism of SERS is explained in this paper.We have carried out research work on SERS substrates,and SERS substrates with low cost,large area and high efficiency were prepared.The main parts are as follows:1?The enhancement mechanism of surface enhanced Raman scattering is introduced.It includes physical enhancement mechanism and chemical enhancement mechanism.The related simulation calculation is introduced in detail?including the finite-difference time-domain method and the finite element method of electromagnetic field?.One of the prepared structures has been simulated and analyzed by the finite-difference time-domain method.2?A kind of SERS substrate was proposed.Three-layer structure consists of Au particles-thin dielectric buffer film-Au particles.The structure is prepared by deposition of thin films and annealing process.First,we get the dense distribution of metal particles.The strong local electric field and the plasmon near-field hot spots existed in the densely distributed metal particles can produce ultra-high detection capability.Secondly,the dense stacked Au particles are combined with the ultra-thin dielectric thin films.It is shown that it can also provide additional enhanced Raman signals.New ideas are provided for the use of semiconductors to enhance SERS technology.3?Another similar SERS substrate is proposed.This SERS substrate is described as Au cluster-Si/SiO₂ thin film-Au cluster structure,and is prepared in the same way as described above.We have found out that the geometry features of the thin metal films can be artificially controlled by a moderate thermal-treatment.It is feasible to form different nano-structures after a suitable choose of film's thickness,the temperature and operating time of thermal annealing.At the same time,the optical properties and SERS performance of the structure are analyzed.It is a feasible method to enhance Raman signal by ultra-thin dielectric film.4?The preparation process of SiO₂ microspheres was introduced in detail.Monodisperse SiO₂ microspheres with the size of 410 nm were prepared by sol-gel method.SiO₂ colloid crystals were synthesized by self-assembly method.Gold Films deposited on silica colloidal crystals by magnetron sputtering,and a relative low temperature is used anneal-treatment for the structure,then the simple method of chemical etching was used to etch the samples.There are a lot of nano-gaps in the composite structure.It is proved that the nano-gap can improve the SERS effect.