Design And Experimental Studies On Porous Silicon Gas Sensor

Sensing technique based on porous silicon film is a new technique developed in the 1990s. Studies on sensitivity characterizations of porous silicon to volatile gases are mainly focused on its electrical aspects. However, in harsh environment, electrical contacts may cause explosion or fire. So Studies on porous silicon sensing techniques based on its optical properties are urgent and have huge potential.Firstly, the paper introduces basic concepts on optical properties of porous silicon, and obtains relations of those optical parameters making use of K-K relation. Then, procedures on how to obtain optical parameters from known reflectance spectra are deduced.Thereafter, porous silicon samples with good performances are fabricated and its reflectance spectra are measured with self-constructed equipments. Thus, optical spectra are got experimentally. At the same time, effects of incident light and porosity on those parameters are studied, which makes steps to optimize optical performances and to study sensing techniques based on optical properties.At last, taking several types of volatile gases as example, employing reflectance peak shift of porous silicon, the paper carries out experiments on sensing studies of porous silicon. Meanwhile, regarding porous silicon as one-dimensional photonic crystal, the paper simulates reflectance characterizations of porous silicon microsensor before and after exposing gases.Due to instability and large line-width, detecting organic gases with reflectance shift of porous silicon directly brings serious error to experiments. Therefore, the paper from many points optimizes experimental conditions in that pulsed electrochemical etching technique, orthogonal experimental method,and anodic oxidization surface aftertreatment process are adopted. More important, the paper adopts porous silicon microcavity which can realize narrow-band emission to study its sensing studies.Compared to previous studies, studies on optical sensing techniques based on resonant peak shift in reflectance spectrum are non-contact, easy-to-do and more precise.