Optical sensing nanostructures for porous silicon rugate filters

Sha Li,Dehong Hu,Lintao Cai,Jianfeng Huang

doi:10.1186/1556-276x-7-79

Abstract

Porous silicon rugate filters [PSRFs] and combination PSRFs [C-PSRFs] are emerging as interesting sensing materials due to their specific nanostructures and superior optical properties. In this work, we present a systematic study of the PSRF fabrication and its nanostructure/optical characterization. Various PSRF chips were produced with resonance peaks that are adjustable from visible region to near-infrared region by simply increasing the periods of sine currents in a programmed electrochemical etching method. A regression analysis revealed a perfect linear correlation between the resonant peak wavelength and the period of etching current. By coupling the sine currents with several different periods, C-PSRFs were produced with defined multiple resonance peaks located at desired positions. A scanning electron microscope and a microfiber spectrophotometer were employed to analyze their physical structure and feature spectra, respectively. The sensing properties of C-PSRFs were investigated in an ethanol vapor, where the red shifts of the C-PSRF peaks had a good linear relationship with a certain concentration of ethanol vapor. As the concentration increased, the slope of the regression line also increased. The C-PSRF sensors indicated the high sensitivity, quick response, perfect durability, reproducibility, and versatility in other organic gas sensing.

Highlights

Porous silicon [PSi], a material with unique structural and optical properties, can be prepared by anodic etching of silicon in ethanolic hydrofluoric acid solution [1,2,3]
In summary, we have presented a systematic study on the preparation of PSRFs with resonant peaks varying from the visible region to the near-infrared region
Those PSRFs were electrochemically produced in a program-controlled current etching by systematically tuning the periods of the sine currents

Summary

Introduction

Porous silicon [PSi], a material with unique structural and optical properties, can be prepared by anodic etching of silicon in ethanolic hydrofluoric acid solution [1,2,3]. One kind of C-PSRF was designed with two peaks in their reflectance spectra and combined with two multilayered mirrors, among which the hydrophobic one was at the top and the hydrophilic one, at the bottom [10,11] These C-PSRFs have been used to manipulate the movement of liquid droplets [10] and local heating [11]. Another kind of C-PSRF was constituted by combined multilayered mirrors and generated by coupling n sine waves with different frequencies used for PSRF preparation [12]. The nanostructure and optical characterization have not been studied systematically

Methods

Results

Conclusion