基于FDTD仿真的高增益拉曼镀金针尖的可重复准确制备

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

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5~100 nm,中间过渡层材料分别为5 nm的SiO_(2),Ta_(2)O_(5),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:50 nm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7 s,镀Au时间120 s,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。

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 5 nm concluding SiO_(2),Ta_(2)O_(5),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 50 nm 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 7 s and 120 s 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.