于FDTD仿真的高增益拉曼镀金针尖的可重复准确制备

提出一种可适用于针尖增强拉曼系统(TERS)的基于时域有限差分法(FDTD)的高增益拉曼针尖及其制备方法。在汇聚光条件下,仿真分析镀Au厚度为5～100nm,中间过渡层材料分别为5nm的SiO₂,Ta₂O₅,Ti,Cu的内凹型W针尖,在Au基底金半球样品处的近场电场分布情况。仿真结果表明:50nm镀金厚度,Ti,Cu为中间层的针尖具有更强的增强效果。在此基础上通过磁控溅射,设定镀Ti时间7s,镀Au时间120s,成功制备出所设计的高增益针尖,通过聚焦离子束(FIB)沿轴向切割针尖并借助扫描电镜(SEM)观察针尖剖面结构,验证该镀膜针尖的尺寸形状等结构参数达到设计要求。经4批次,每批次20根针尖进行重复镀膜实验,从而证明所设计的针尖稳定可重复准确制备。

Reproducible and Accurate Fabrication of High Gain Raman Gold Plated Tips Based on FDTD Simulation

A high gain Raman tip suitable for tip enhanced Raman system (TERS) based on finite difference time domain (FDTD) simulation and its preparation methods are put forward. The near-field electric field distribution of the concave tungsten tip with gold plating thickness of (5～100)nm and with intermediate transition layer materials of 5nm concluding SiO2, Ta2O5, Ti, Cu is simulated and analyzed at the gold hemispherical sample on the gold substrate. The simulation results show that the tip with a gold plating thickness of 50nm and intermediate interlayer of Ti and Cu have the strongest enhancement effect. On this basis, the designed high-gain tip was successfully prepared by magnetron sputtering and the titanium plating time was set at 7s and 120s for gold plating. The tip was cut by focusing ion beam (FIB) and the profile structure of the tip was observed by a scanning electron microscope (SEM), and the size and shape of the coated tip were verified to meet the design requirements. After 4 batches of 20 needles in each batch, repeated coating experiments were carried out, which proved that the designed needles were stable and could be prepared repeatedly.