State Key Laboratory of Precision Measuring Technology & Instruments, Centre of MicroNano Manufacturing Technology, Tianjin University, Tianjin 300072, China.
Nanoscale Res Lett. 2012 Jul 17;7(1):399. doi: 10.1186/1556-276X-7-399.
A novel method with high flexibility and efficiency for developing SERS substrates is proposed by patterning nanostructures on Si substrates using focused ion beam direct writing (FIBDW) technology following with precise thermal evaporation of gold film on the substrate. The effect of SERS on the substrate was systematically investigated by optimizing the processing parameters and the gold film thickness. The results proved that small dwell time could improve the machining accuracy and obtain smaller nanogap. The Raman-enhanced performance of the substrate was investigated with 10-6mol/L Rhodamine 6 G solution. It was indicated that the elliptic nanostructures with 15-nm spacing on Si substrates, coated with approximately 15-nm thick gold film, have exhibited a high-enhanced performance, but dramatic performance degradation was found as the gold film thickness further increased, which most probably resulted from changes of the nanostructures' morphology such as elliptical tip and spacing. To avoid the morphological changes effectively after depositing gold film, optimization design of the nanostructures for FIBDW on Si substrates was proposed. Besides, a similar phenomenon was found when the gold film was less than 15nm because there was little gold remaining on the substrate. The method proposed in this paper shows a great potential for the higher performance SERS substrates development, which can further reduce the spacing between hot spots.
提出了一种在 Si 衬底上通过聚焦离子束直写（FIBDW）技术在衬底上图案化纳米结构，然后精确热蒸发金膜，从而具有高灵活性和高效率的开发 SERS 衬底的新方法。通过优化处理参数和金膜厚度，系统地研究了 SERS 对衬底的影响。结果表明，小的停留时间可以提高加工精度并获得更小的纳米间隙。使用 10-6mol/L 罗丹明 6G 溶液研究了衬底的拉曼增强性能。结果表明，在 Si 衬底上具有 15nm 间隔的椭圆形纳米结构，涂有约 15nm 厚的金膜，表现出高增强性能，但随着金膜厚度进一步增加，性能显著下降，这很可能是由于纳米结构形态的变化，如椭圆尖端和间隔。为了避免在沉积金膜后有效避免形貌变化，提出了一种针对 Si 衬底 FIBDW 的纳米结构优化设计。此外，当金膜小于 15nm 时也发现了类似的现象，因为在衬底上残留的金很少。本文提出的方法为开发具有更高性能的 SERS 衬底提供了巨大的潜力，可以进一步减小热点之间的间隔。
