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Surface Plasmon Resonance Effects At The Interface Of The Nano Films

Posted on:2013-02-20Degree:DoctorType:Dissertation
Country:ChinaCandidate:M BaoFull Text:PDF
GTID:1118330374467971Subject:Condensed matter physics
Abstract/Summary:PDF Full Text Request
Surface plasmon resonance (SPR) occurs at the interface of metal and dielectric. It use evanescent wave as a probe to detect the optical varity of the medium surface. Since the SPR sensor technology was used in the field of biochemical sensors, it has obtained wide attention in the scientific community and commercial insititutions due to its high sensitivity and real time investigation of biomolecular interaction analysis. It has become the international research focus in the field of chemical detectin, and has been gradually applied in the field of drug screening, food safty, clinical diagnosis and proteomics.First, the research status of SPRsensors and its application is introduced. Then its mechanism and principle of surface Plasmon wave and surface Plasmon resonance are analyzed, and the prism coupled SPR sensor based on Kretschmann structure is emphatically discussed. Matlab software is used to simulate and analyze the spectrum. And build a SPR system based on Kretschmann structure.Second, the thesis investigates the effects of ZnO sensing film thickness on the surface plasmon resonance (SPR) curve. ZnO sensing films with the thickness of20nm,30nm,200nm,220nm and240nm have been deposited onto Ag/glass substrates by RF sputtering and thermally treated at300℃in air for one hour. Theoretical analysis of the sensitivity of the SPR sensors with different ZnO sensing film thickness is discussed, and the results are in agreement with the calculated value. It is demonstrated that SPR sensors with angular interrogation may attain higher sensitivity and can detect larger surface environment refractive index with proper ZnO sensing film thickness.Third, the thesis studies the wave guided wave SPR. Upon using a200nm top layer of dielectric film with a high value of the real part ε of the dielectric function, on top of an SPR sensor in the Kretschmann configuration, the sensitivity is improved. The refractive index effect of dielectric film on sensitivity is usually ignored. Dielectric film with different refractive index were prepared by radio frequency magnetron (RF) sputtering and measured with spectroscopic ellipsometry (SE). The imaginary part ε of the top nano layer permittivity needs to be small enough in order to reduce the losses and get sharper dips. The stability of the sensor is also improved because the nano layer is protecting the Ag film from interacting with the environment. The response curves of the Ag/ZnO chips were obtained by using SPR sensor. Theoretical analysis of the sensitivity of the SPR sensors with different ZnO film refractive index are presented and studied. Both experimental and simulation results show that the Ag/ZnO films exhibit an enhanced SPR over the pure Ag film with a narrower full width at half maximum (FWHM). It shows that the top ZnO layer is effective in enhancing the surface plasmon resonance and thus its sensitivity.Fourth, this work investigates the combination of electrochemistry with surface plasmon resonance (SPR) for obtaining reliably clean gold film surfaces. This method is based on anodic electrodissolution of gold in a weak sulfuric acid. Two modes of SPR measurement, SPR angular scan (R-θ) and the time evolution of the reflectivity change at a fixed angle, were displayed to study the electrodissolution progress of gold film. The angle shift of the resonance minimum recorded before and after cyclic potential scanning allows for the unambiguous measurement of the film thickness change. To assess the change of the surface roughness and morphology of gold film through anodic electrodissolution, atomic force microscopy was used. Peak-current potential-differences obtained from cyclic voltammetry is used to characterize surface cleanliness. A low peak-current potential-difference indicates a cleaner surface. These results show that this approach provides a good way to convert the wastes of gold film with larger thickness into useful materials. The importance of this work is in the use of attenuated total reflection phenomena to characterize electrodissolution progress of gold film.Last, the thesis build a mode based on the Krestchmann configuration to measure the air gap between two Ag films. Due to the presence of double Ag layers, the Fabry-Perot resonance and surface Plasmon tunnel-coupled effects could occur, which cause the SPR angle to shift to larger angles when the air gap decrease to a certain width.
Keywords/Search Tags:surface plasmon resonance, ZnO, electrochemistry, Air gap, surface Plasmon tunnel-coupled
PDF Full Text Request
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