During my microelectronics research, I created various nano-scale samples. Here is a collection of these samples (SiNWs, Ag NP, etc.) seasoned in colorful means. The nanoscopic images establish a connection to the day-to-day world at a different scale. Transcending scientific illustrations, these visually captivating pictures also promote the public interest and acceptance of nanotechnology.
nano technology publications
Abstract: Well-ordered SiNWs are applied as surface-enhanced Raman scattering (SERS) substrates. Laser interference lithography is used to fabricate large-area periodic nanostructures. By controlling the reaction time of metal assisted chemical etching, various aspect ratios of 3D SiNWs are generated. Ag nanoparticles are decorated on the substrates via redox reaction to allow a good coverage of Ag over the SiNWs. As the height of the SiNWs increases, the light scattering inside the structures is enhanced. The number of the probing molecules within the detection volume is increased as well. These factors contribute to stronger light-matter interaction and thus lead to higher SERS signal intensity. However, the light trapping effect is more significant for higher SiNWs, which prevents the detection of the SERS signals. An optimized aspect ratio ~ 5:1 (1 µm height and 200 nm width) for the SiNW array is found. The well-ordered SiNWs are also demonstrated better SERS signal intensity and uniformity than the randomly arranged SiNWs.
Author: Jing Yang, Jiabao Li, Qihuang Gong, Jinghua Teng & Minghui Hong
Abstract: Surface enhanced Raman spectroscopy (SERS) has been widely investigated as an effective technique for low-concentration bio-chemical molecules detection. A rapid two-step approach to fabricate SERS substrates with high controllability in ambient air is developed. Dynamic laser ablation directly creates microgroove on the Si substrate. Meanwhile, nanoparticles are synthesized via the nucleation of laser induced plasma species and the air molecules. It configures the Si surface into four different regions decorated with nanoparticles at different sizes. With Ag film coating, these nanoparticles function as hotspots to enhance SERS signals. Microsquare arrays are fabricated on the Si surface as large-area SERS substrates by the laser ablation in horizontal and vertical directions. In each microsquare, it exhibits quasi-3D structures with randomly arranged and different shaped nanoparticles aggregated in more than one layers. With Ag film deposition, uniform SERS signals are obtained by detecting the 4-methylbenzenethiol molecules. The SERS signal intensity is determined by the size and shape distributions of the nanoparticles, which depend on the laser processing parameters. With the optimal laser ablation process, the SERS signals show a uniform enhancement factor up to 5.5 x 106. This provides a high-speed and low-cost method to produce SERS substrates over a large area.