Liao Yanjuan, Huang Jingnan, Huang Xu, Jiang Shaoji
State Key Laboratory of Optoelectronic Materials and Technologies, Guangzhou, 510275, People's Republic of China; School of Physics and Engineering, Sun Yat-Sen University Guangzhou, 510275, People's Republic of China.
J Nanosci Nanotechnol. 2018 Apr 1;18(4):2803-2810. doi: 10.1166/jnn.2018.14539.
Noble metal sculptured thin films have attracted great research interest last decade as competitive surface-enhanced Raman scattering (SERS) substrates. However, the influences of the deposition conditions and the morphology on the plasmonic properties and SERS performance of the metal sculptured thin films have not been well understood due to the complexities of the morphology. In this work, the influences of the deposition angle and the height are investigated in both experiment and numerical simulation. A more accurate geometrical model based on the binarized scanning electron microscope images has been utilized to study the near-field plasmonic properties of Ag column thin films by taking account of the geometry irregularities, size distributions and random arrangement of the columns. It's found that the cross-sectional electric field enhancement is mainly dominated by the column density. When the deposition angle increases from 68° to 82° the SERS enhancement factors increases monotonously due to the increase of the self-shadow effect. While with the increase of height the SERS enhancement factors firstly increase to the largest value of 3.05 × 108 at the thickness of 694 nm then decrease because of competitive growth mechanism during the deposition. The detection limit of the optimized sample is found to be lower than 10-12 M. Our work could be helpful in understanding the SERS mechanism and useful to the optimization of metal sculptured thin films as SERS substrates.
在过去十年中，贵金属雕刻薄膜作为具有竞争力的表面增强拉曼散射（SERS）基底引起了极大的研究兴趣。然而，由于其形态的复杂性，沉积条件和形态对金属雕刻薄膜的等离子体特性和SERS性能的影响尚未得到很好的理解。在这项工作中，通过实验和数值模拟研究了沉积角度和高度的影响。基于二值化扫描电子显微镜图像建立了更精确的几何模型，考虑到柱体的几何不规则性、尺寸分布和随机排列，研究了银柱薄膜的近场等离子体特性。研究发现，横截面电场增强主要由柱体密度主导。当沉积角度从68°增加到82°时，由于自阴影效应的增加，SERS增强因子单调增加。而随着高度的增加，SERS增强因子首先在厚度为694 nm时增加到最大值3.05×108，然后由于沉积过程中的竞争生长机制而降低。优化后的样品检测限低于10-12 M。我们的工作有助于理解SERS机制，并有助于优化作为SERS基底的金属雕刻薄膜。
