High-Throughput Fabrication of Ultradense Annular Nanogap Arrays for Plasmon-Enhanced Spectroscopy

Abstract

The confinement of light into nanometer-sized metallic nanogaps can lead to an extremely high field enhancement, resulting in dramatically enhanced absorption, emission, and surface-enhanced Raman scattering (SERS) of molecules embedded in nanogaps. However, low-cost, high-throughput, and reliable fabrication of ultra-high-dense nanogap arrays with precise control of the gap size still remains a challenge. Here, by combining colloidal lithography and atomic layer deposition technique, a reproducible method for fabricating ultra-high-dense arrays of hexagonal close-packed annular nanogaps over large areas is demonstrated. The annular nanogap arrays with a minimum diameter smaller than 100 nm and sub-1 nm gap width have been produced, showing excellent SERS performance with a typical enhancement factor up to 3.1 × 10 and a detection limit of 10 M. Moreover, it can also work as a high-quality field enhancement substrate for studying two-dimensional materials, such as MoSe. Our method provides an attractive approach to produce controllable nanogaps for enhanced light-matter interaction at the nanoscale.

Engineering Colloidal Lithography and Nanoskiving to Fabricate Rows of Opposing Crescent Nanogaps

“…Nanogaps between two noble metal nanostructures can “squeeze” light, leading to extreme confinement of electro–magnetic energy, which can significantly enhance the surface enhanced Raman scattering (SERS) of detection molecules adsorbed in the nanogaps. [ 50,51 ] Benefiting from the advantages of the conventional thin film deposition technology, we have successfully fabricated CNGs, which are comprising two parallel crescent‐shaped nanowires with a spacing of sub‐10 nm. The fabrication process is successively depositing gold (110 nm)/aluminum (4 nm)/gold (110 nm) sandwich films on the close‐packed colloidal monolayer in the deposition step (Figure 1b) and then perpendicularly section the sample by ultra‐microtome.…”

Unpacking the toolbox of two-dimensional nanostructures derived from nanosphere templates

“…223 Moreover, integration of the colloidal-based surface patterning with other lithography/patterning methods may be widely applied. 309 Thus, the rational design of the integration method for specific materials, nanostructures, or devices is important. With great advances achieved, it is expected to further apply the colloidal-based surface patterning in extensive fields with the aid of improved template quality, preparation methods, and the emerging properties.…”

Scalable Fabrication of Metallic Nanogaps at the Sub‐10 nm Level

“…arrays, [123] and the use of optical interference lithography [101,124] to pre-pattern the first metal layer instead of using FIB/EBL methods. Overall, ALL has proven itself to be a versatile and highly scalable method for patterning nanogaps and nanogap arrays with extremely small gap-widths.…”

“…Various modifications to standard ALL have been reported, including the replacement of the physical peeling step by chemical etching to improve the yield and the robustness of the final structures, [ 122 ] the combination of ALL with nanosphere lithography to permit the patterning of large‐area (3 cm 2 ) nanogap arrays, [ 123 ] and the use of optical interference lithography [ 101 , 124 ] to pre‐pattern the first metal layer instead of using FIB/EBL methods. Overall, ALL has proven itself to be a versatile and highly scalable method for patterning nanogaps and nanogap arrays with extremely small gap‐widths.…”