High aspect ratio SiNW arrays with Ag nanoparticles decoration for strong SERS detection

• Published in: Nanotechnology Vol. 25; no. 46; pp. 465707 - 6
• Main Authors: Yang, J, Li, J B, Gong, Q H, Teng, J H, Hong, M H
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 21.11.2014; Institute of Physics
• Subjects: Arrays; Aspect ratio; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Decoration; Exact sciences and technology; Low-dimensional structures (superlattices, quantum well structures, multilayers): structure, and nonelectronic properties; Materials science; Methods of nanofabrication; Nanocrystalline materials; Nanolithography; Nanoparticles; Nanoscale materials and structures: fabrication and characterization; Nanostructure; nanowires; Physics; Quantum wires; Raman scattering; Silicon substrates; Silver; surface enhanced Raman scattering; surface plasmons; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Lithography; Light scattering; Interference; Nanostructures; Chemical etching; Aspect ratio; Nanoparticles; Trapping; Redox reactions; SERS; Silicon; Nanowires; Arrays; Nanostructured materials
• ISSN: 0957-4484; 1361-6528
• DOI: 10.1088/0957-4484/25/46/465707

Well-ordered silicon nanowires (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 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 m height and 200 nm width) for the SiNW array is found. The well-ordered SiNWs demonstrate better SERS signal intensity and uniformity than the randomly arranged SiNWs.