Porous Silicon Structures as Optical Gas Sensors (original) (raw)

Gas detection with a porous silicon based sensor

Sensors and Actuators B-chemical, 2000

Porous silicon PS layers with 60% porosity and 80 mm thick were prepared from n-type silicon wafer. We present the sensitivity of PS photoluminescence to 250 ppm of carbon monoxide. Besides the variation of conductivity of the device due to presence of organic vapors such as chloroform, methanol, ethanol and toluene have been carried out. q 2000 Elsevier Science S.A. All rights reserved.

Electro-optical porous silicon gas sensor with enhanced selectivity

Sensors and Actuators B: Chemical, 2010

A new type of gas sensor that enables simultaneous monitoring of the electrical and optical properties of the sensor structure has been developed. The sensor is based on a porous silicon (PS) optical interference filter layer, which was produced with an electrochemical etching process. This sensor structure provides a rapid response when subjected to ambient adsorbates. In addition, it offers an increased level of selectivity between different gases, thus addressing the unresolved problems related to PS gas sensing. Sensors with differing hygroscopic properties were produced, and their response to changes in relative humidity were tested. The sensors were also subjected to ethanol and dimethylformamide vapours, and their ability to differentiate between the studied gases was demonstrated.

Multiparametric porous silicon gas sensors with improved quality and sensitivity

Physica Status Solidi (a), 2003

We have fabricated a multiparametric gas sensor based on porous silicon. The sensing parameters are the electrical conductivity of a single porous Si layer and the resonance wavelength of a porous silicon microcavity, both fabricated on the same substrate. The electrical conductivity allows detection of 50 ppb of nitrogen dioxide in dry air. Although relative humidity also affects the electrical conductivity, the contributions due to nitrogen dioxide and to humidity can be distinguished by simultaneously monitoring the cavity resonance wavelength and the current. We also demonstrate a three-contact configuration which further increases the sensitivity of the electrical response of the sensor.

Novel Design of Porous Silicon Based Sensor for Reliable and Feasible Chemical Gas Vapor Detection

Journal of Lightwave Technology, 2013

In this study, an innovative design for porous silicon (PSi) based sensors is proposed to eliminate some problems of conventional PSi sensors such as undesired reflections from imprecise positioning of the fiber optic cable and the PSi structure. Our design has three stages as hole milling for fiber socket, fabrication of filter structure, and integration of the fiber optic cable to the bulk Si. We have carried out reflectivity measurements of alcohols with close refractive index values by the proposed and conventional sensors. From the measurements, we note that both sensors have equal sensitivity in identifying alcohols, that repeatability of our proposed sensor is relatively higher, and that our sensor allows easy positioning and flexibility in sensing applications. Nonetheless, our proposed sensor necessitates a thorough fabrication process and a methodological preparation.

Fabrication and Characterization of a Sensing Device Based on Porous Silicon

Physica Status Solidi (a), 2000

In this work we have fabricated a simple gas-sensing device based on porous silicon. Starting from the well-known porous silicon photoluminescence quenching due to oxygen, we have optimized the material and the device design, obtaining a reversible and stable O 2 gas sensor. A simple and cheap detector of air leaks in inert environment is of great interest for the alimentary industry. Full characterization of the device has been carried out in a gas sensor calibration apparatus, showing even a promising sensitivity at room temperature to a toxic gas like NO 2 .

Optical sensors for vapors, liquids, and biological molecules based on porous silicon technology

Nanotechnology, …, 2004

The sensing of chemicals and biochemical molecules using several porous silicon optical microsensors, based both on single-layer interferometers and resonant-cavity-enhanced microstructures, is reported. The operation of both families of sensors is based on the variation of the average refractive index of the porous silicon region, due to the interaction with chemical substances either in vapor or liquid state, which results in marked shifts of the device reflectivity spectra. The well established single-layer configuration has been used to test a new chemical approach based on Si-C bonds for covalent immobilization of biological molecules, as probe, in a stable way on the porous silicon surface. Preliminary results on complementary oligonucleotide recognition, based on this technique, are also presented and discussed. Porous silicon optical microcavities, based on multilayered resonating structures, have been used to detect chemical substances and, in particular, flammable and toxic organic solvents, and some hydrocarbons. The results put in evidence the high sensitivity, the reusability, and the low response time of the resonant-cavity-enhanced sensing technique. The possibility of operating at room temperature, of remote interrogation, and the absence of electrical contacts are further advantages characterizing the sensing technique.

Gas Sensing Properties of Porous Silicon

Analytical Chemistry, 1995

Conductivity of porous silicon layers (ptype) has been investigated for oxganic vapor sensing. A many orders of magnitude increase in conductivity in response to a vapor pressure change from 0 to 100% has been measured for some compounds. The conductivity (at a constant pressure) varies exponentially with the compound's dipole moment. The temporal response of the porous silicon layers is in the seconds range, and the recovery is much slower (minutes). However, due to the tremendous conductivity changes and the low background noise, a complete recovery is not needed for sensing purposes. The mechanism of conductivity enhancement has been studied us@ several methods. It is attributed to an increase in the density of charge carriers. An additional mechanism based on increased diffusMty may take place in microporous silicon. The observed characteristics suggest the application of porous silicon to future chemical sensors. The sensors have the potential to be integrated monolithidly with other silicon devices using current technologies. Porous silicon CpS) is becoming an increasingly important electronic material in current fabrication technology. It has been suggested as a potential optical material for new silicon light emitting The fabrication of this material is carried out by a very simple electrochemical etching of silicon, which creates a network of nanometer-sized Si structures. Extensive studies have already been carried out on the electro-and photoluminescence properties of this material. Several models have been proposed to explain the origin of light emission, including quantum codnement effects,1s2J0J radiative recombination via (1) Canham, L. T.

CHx - porous silicon structures for gas sensing applications

physica status solidi (c), 2005

We have developed a gas sensor for hydrocarbons using layered structures hydrocarbons /porous silicon. Sensitivity of this device, response time and capacitance response to different gases (ethane, ethylene and propane) have been studied. DC and AC electrical measurements were performed to test the sensor and it has been shown that CH x layer-PS/p-Si structure is modified by the gas reactivity on the PS/CHx surface. Finally, FTIR spectroscopy measurements in different gas environments have shown remarkable change of chemical composition of the sensor material as a result of its interaction with gases.

Porous Silicon Based Sensor for Organic Vapors

Acta Physica Polonica A, 2015

Porous silicon (PS) has been an attractive material for enhancing optical properties of silicon. Its large surface area for sensor applications and compatibility with silicon-based technologies has been a driving force for further technology development. In this study, ability of PS to sense at room temperature organic vapors such as acetone, trichloroethylene and hexane, which are harmful to human health, has been investigated. Electrical (DC) and photo-luminescence (PL) measurements in a controlled atmosphere (nitrogen gas and an organic vapor mix) were performed to test the sensor response towards the organic vapors. It was found that PS surface is very sensitive against these vapors. The experimental results also suggested that PS can be used as a new electro-optical material to sense harmful vapors.