Fast, Economical, and Reproducible Sensing from a 2D Si Wire Array: Accurate Characterization by Single Wire Spectroscopy

Abstract

Silicon (Si) is promising as a field enhancement material because of its high abundance, low toxicity, and high refractive index. The field enhancement effect intensifies light–matter interactions, which improves photocatalysis, solar cell performance, and sensor sensitivity. To manufacture field enhancement materials on a production scale, the fabrication technique must be simple, cost-effective, fast, and highly reproducible and must produce a high enhancement factor (EF). Herein, we report on an economical and efficient fabrication method for a field enhancement substrate consisting of a two-dimensional Si wire array (2D-SiWA). This substrate was demonstrated as a fluorescence sensor with high sensitivity (EF > 200) and composed of a large area (6.0 mm2). In addition, single wire spectroscopy was used to identify very high reproducibility of the sensor sensitivity in regular regions (97%) and a mixture of regular and irregular regions (87%) of the 2D-SiWA. The large-area Si fluorescence sensor fabrication was cost-effective and rapid and was 50× less expensive, 20×faster, and 60,000×larger than the typical electron beam lithography method.

Large-Area Plasmon Mapping via an Optical Technique: Silver Nanohole Array and Nano-Sawtooth Structures

“…In addition, if the cost of constructing a clean room is included in our estimation of the costs of the EBL method, then the alternative method presented in this paper is more than 50 times more cost-effective. Comparing the production times, our method requires only 1/10 of the time of the EBL method. − , Thus, the cost-effective new method presented in this article produces effective field enhancement substrates and offers significant time savings.…”

“…Indeed, the EF error bars in Figure b,c are a result of the non-uniformity of the Ag nanostructures prepared in this study. If improved structures could be prepared, then the EF values would be more uniform; specifically, our target would be to obtain the 97% uniformity that we achieved for Si wire array structures . Second, increasing the active area as much as possible is a priority.…”

“…Comparing the production times, our method requires only 1/10 of the time of the EBL method. [25][26][27][28][29][30][31]39 Thus, the cost-effective new method presented in this article produces effective field enhancement substrates and offers significant time savings.…”

“…If improved structures could be prepared, then the EF values would be more uniform; specifically, our target would be to obtain the 97% uniformity that we achieved for Si wire array structures. 39 Second, increasing the active area as much as possible is a priority. For instance, subjecting samples to different physical (e.g., multiple scratching and/or dry etching) or chemical (e.g., wet etching) treatments should produce saw-tooth structures with larger areas and higher EF values.…”

“…The fluorescence spectra of a crystal violet (CV) dye solution were acquired using confocal spectromicroscopy as described elsewhere. − Briefly, a long-working distance objective lens was used to collect the spectrum of the sample solution under a cover glass within an optical cell. The optical cell was designed to allow the detection of signals from a solution layer between the cover glass and Ag nanostructures.…”