Department of Energy Science, Sungkyunkwan University (SKKU), Suwon 16419, Republic of Korea.
Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), Suwon 16419, Republic of Korea.
Sci Rep. 2017 Jan 13;7:40810. doi: 10.1038/srep40810.
We successfully achieve the tip-enhanced nano Raman scattering images of a tungsten disulfide monolayer with optimizing a fabrication method of gold nanotip by controlling the concentration of etchant in an electrochemical etching process. By applying a square-wave voltage supplied from an arbitrary waveform generator to a gold wire, which is immersed in a hydrochloric acid solution diluted with ethanol at various ratios, we find that both the conical angle and radius of curvature of the tip apex can be varied by changing the ratio of hydrochloric acid and ethanol. We also suggest a model to explain the origin of these variations in the tip shape. From the systematic study, we find an optimal condition for achieving the yield of ~60% with the radius of ~34 nm and the cone angle of ~35°. Using representative tips fabricated under the optimal etching condition, we demonstrate the tip-enhanced Raman scattering experiment of tungsten disulfide monolayer grown by a chemical vapor deposition method with a spatial resolution of ~40 nm and a Raman enhancement factor of ~4,760.
我们通过优化电化学刻蚀过程中蚀刻剂浓度的方法成功实现了二硫化钨单层的尖端增强纳米拉曼散射图像。通过将方波电压施加到浸入不同比例盐酸乙醇混合溶液中的金丝线上，我们发现尖端的圆锥角和曲率半径都可以通过改变盐酸和乙醇的比例来改变。我们还提出了一个模型来解释尖端形状变化的原因。通过系统研究，我们找到了一种最佳的条件，可实现约 60%的产率，尖端半径约为 34nm，圆锥角约为 35°。使用在最佳刻蚀条件下制备的代表性尖端，我们展示了通过化学气相沉积方法生长的二硫化钨单层的尖端增强拉曼散射实验，空间分辨率约为 40nm，拉曼增强因子约为 4760。
