Research On SPR Differential Phase Detection Method For Thickness Measurement Of Bimetallic Layer

Thin film materials,especially metal thin films,are becoming more and more important in various application fields due to their excellent electrical,optical,mechanical,gas sensing and superconducting properties.They are becoming more and more important in the military,petrochemical,heavy industry,light industry and other fields.The thin film we studied is a kind of single layer or multilayer film composed of nanoscale grain.Its properties are not only affected by the material properties,but also by its surface structure and thickness.Therefore,in order to deeply explore the characteristics of the film material,it is very important to measure the thickness of the film accurately.The purpose of this paper is to improve the design of surface plasmon resonance(SPR)phase measurement method developed by our research laboratary and its resolution for nanoscale bimetallic layer thickness detection.This paper analyzes the characteristics of several commonly used detection methods of metal film thickness at first,and focuses on the methods of how to detect the parameters of bimetallic metal film by using the SPR method.Based on the SPR theory and previous results of phase detection method,this thesis carries out the research on differential SPR phase detection method.The laser illuminates the SPR coupling prism with resonance angle to excite the surface plasmon resonance of the bimetallic metal film,then the beam will reflect the phase changes in the offset of the interference fringes after passing the interference structure.The resolution and sensitivity of SPR phase detection are improved by the method of angle differential phase measurement,and the thickness of the bimetallic metal film is calculated by the correlation calculation of interference fringes.The differential phase SPR detection system is determined according to the simulation results and detection method.The optical path of differential phase SPR detection system is built and experiments are carried out.The slope of the interference fringe curves are calculated according to the relation between the fitting differential phase change and the incident angle,then the film thickness of Ag and Au bimetallic layer film is obtained.Finally,this paper analyzes the error factors that may affect the effect of experimental measurements.The simulation and experimental results show that the differential phase SPR measurement for the thickness of Ag and Au bimetallic layer film is achieved.Moreover,the comparison of this design scheme and the experimental results show that the differential measurement method can achieve the goal of this paper.