Photonic crystals based on silicon nanoholes array for biosensing applications

Abstract

In this article, we report Si-based nanohole array structures for biosensing applications. These photonic crystal structures were fabricated by the combination of deep-UV lithography and dry etch techniques. The fabricated structures support guided modes for near-infrared (IR) wavelengths, which can be used for the detection of analyte molecules bound to the surface. The sensing performance of the structure was evaluated in terms of surface and bulk refractive index sensitivity by spectroscopic reflection measurement. Bulk refractive index sensitivity (BRIS) was evaluted in solution with glycerol diluted in deionized (DI) water and found to be 139 nm/RIU (refractive index unit). To study surface sensitivity, oxide layers with different thicknesses were employed as as model analytes. The oxides were deposited by atomic layer deposition (ALD) on top of the structure. Moreover, an experiment with another model analyte present in solution, avidin, using various concentrations in phosphate-buffered saline (PBS) solutions allowed to estimate the limit of detection (LoD = 236 ng/mL) and quantification (LoQ = 9367 ng/mL) of our device.