Local Cracking‐Induced Scalable Flexible Silicon Nanogaps for Dynamically Tunable Surface Enhanced Raman Scattering Substrates

Abstract

Surface enhanced Raman scattering (SERS), as a promising and convenient analytical tool for molecule sensing, has turned out to be one of the most important applications of plasmonic nanostructures. However, its large‐area production, controllability, and adjustability remain significant challenges because of the weak control over the fabrication and spatial arrangement. Herein, a silicon nanogap array‐based flexible plasmonic substrate is developed, with capabilities of large‐area production, controllable arrangement, and width of nanogaps, by utilizing the standard microfabrication platform, and the fabricated flexible plasmonic substrate is further explored for dynamically tunable SERS for molecular sensing. After experimentally and theoretically optimizing the geometric designs of precursors, a 90 × 90 silicon nanogap array (over 1 cm × 1 cm) with a yield of about 99.74% is achieved. SERS is realized by depositing Au films onto the silicon nanogap. Dynamically tunable SERS is demonstrated by the thermally induced local stretch or contraction of silicon nanogaps, where the key parameters including Raman enhancement and sensitivity of the molecular sensor can be conveniently adjusted. These presented results significantly expand the scope of engineering opinions for flexible plasmonic nanostructures, which have many envisioned applications especially for environmental monitoring and biochemical detection.

Wafer-Scale Fabrication and Transfer of Porous Silicon Films as Flexible Nanomaterials for Sensing Application

“…Flexible substrates attracted much attention in SERS due to the advantage in tunable plasmonic resonances and directly collecting analyte from the curved surface [ 38 , 39 , 40 , 41 , 42 , 43 ]. As a further proof of the flexibility of our fabricated SERS substrate, the flexible SERS substrates were used for detection of pesticide residues on apple surface with a real curved surface.…”

Efficient concentration of trace analyte with ordered hotspot construction for a robust and sensitive SERS platform

“…In these substrates, the nanostructure plays two roles: one is to increase roughness for hydrophobicity, and the other is to provide plasmonic hotspots. However, limited by the processing difficulty of micro/nano hierarchical structures, these plasmonic hot spots are usually disordered and size-uncontrolled, especially when attempting to create the nanogap with sub-10 nm, which is considered to be capable of the strongest near-field enhancement [24]. Scheme 1(a) shows the two routes mentioned above with different structural designs for SERS performance.…”