设计了一种表面镀有Ag涂层且具有内凹弧度的圆锥形钨(W)针尖, 运用时域有限差分法建立了针尖-球形样品结构的针尖增强喇曼散射模型, 研究了针尖增强效应及参数优化配置.采用波长632.8 nm光源斜入射激励方式, 对模型的针尖增强喇曼散射效应进行电磁场仿真计算, 获得了模型在不同光源入射角度、样品粒径、针尖-样品间距下的增强电场强度和针尖增强喇曼散射增强因子.研究结果表明: 当光源入射角为72°、样品粒径约为140 nm、针尖-样品间距达到2 nm时可产生最大的增强因子, 达到104量级.该结果为制备高增强效率的探针针尖, 及其在高空间分辨率和高检测灵敏度喇曼光谱仪中的实用化提供了参考依据.

A new tip-enhanced Raman scattering(TERS) model was established by finite difference time domain (FDTD) method, which included a conical tungsten tip with concave arc and silver-coated and a gold nanoparticle. The enhancement effectandparameter optimizationof the TERS model wereinvestigated. Under 632.8 nmwavelength laser excitation, three-dimensional electromagnetic simulations were carried out forthe TERS effect with different conditions, and the simulation resultswerepresented and discussed. The results indicate thatthis TERS model has the maximum field enhancement factor when the incident angle is 72°, the sample diameter is about 140 nm and the tip sample gap is reach 2 nm. The conclusion provides a reference for developing higher efficiency enhancingmetal tips and the Raman spectrometer with best performance.