Porous Silicon Based Sensor for Organic Vapors (original) (raw)
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Photonics, Devices, and Systems II, 2003
Photoluminescence quenching response of as prepared and surface modified porous silicon sensors in presence of organic analytes in gas phase was studied. Surface modification aimed at increasing of operational stability and modification of sensoric response was performed by a hydrosilylation reaction with various organic compoundsmethy l lO-undecenoate, haemin, cinchonine and quinine. These sensors were tested for a homological set of aliphatic alcoho ls from methanol to hexanol. We have systematically measured changes in porous silicon photoluminescence inte nsity as a function of concentration of detected analytes and evaluated sensitivity, detection limit and linear dynamic range of our sensors. Speed of the sensoric response was of the order of seconds. The obtained sensoric parameters were correlated with chemical and physical properties of both the compounds used for derivatization and the detected analytes.
Determination of sensoric parameters of porous silicon in sensing of organic vapors
Materials Science and Engineering: C, 2002
Ž. Ž. Photoluminescence PL properties of as-prepared and surface derivatized porous silicon PS in the presence of organic compounds in gas phase were studied. Surface derivatization, aimed at increasing stability of porous silicon properties, was performed by Lewis acid mediated hydrosilylation with methyl 10-undecenoate. We have systematically measured changes in photoluminescence intensity for a set of alcohols from C to C. From the variation of the photoluminescence quenching response as a function of alcohol concentration, we 1 6 determine the sensitivities and detection limits of our porous silicon sensors and these correlate with physical and chemical properties of studied species. For methyl 10-undecenoate derivatized PS samples, we have observed a remarkable enhancement of the selectivity for
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.
Organic Vapors Sensor Based on Photosynthesize Porous Silicon
2012
In this paper, a photo synthesis porous silicon (PS) layer is investigated as a sensing material to detect the organic vapors with low concentration. The structure of the sensor consisted of thin Al/PS/n-Si/Al, where the PS was etched photo chemically. The current response of the sensor is governed by the partial depletion of silicon located between two adjacent (porous regions). This depletion is due to the charges trapped on the surface states associated with the silicon – native silicon oxide.
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.
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.
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 .
Sensors and Actuators B: Chemical, 2004
Photoluminescence response of porous silicon in presence of single organic analytes scales within the linear dynamic range with concentration of detected species. We present systematic study of changes in porous silicon photoluminescence intensity in the presence of precisely controlled amounts of linear aliphatic alcohols (from methanol to n-hexanol) in gas and liquid phases. From the concentration dependence of photoluminescence quenching we determined sensitivity of porous silicon sensor response. The sensor response sensitivity revealed nearly monotonous change within the homological set of n-alcohols in both gas and liquid phases. However, while in gas phase the sensitivity of sensor response rose with the length of alcohol chain, in liquid phase we observed the opposite behavior. The mechanism of sensor response in gas and liquid phases is explained by photoluminescence dielectric quenching. The strength of photoluminescence quenching is directly determined by dielectric constant and concentration of analyte in liquid phase whereas in gas phase it primarily depends on effective concentration of analyte inside porous silicon matrix. The thermodynamic equilibrium concentration of analyte inside porous silicon matrix is controlled by capillary condensation effect. A very good correlation between gas phase concentration and room temperature saturated vapor pressure of studied analytes and porous silicon photoluminescence quenching response was obtained.
Smart Optical Sensors for Chemical Substances Based on Porous Silicon Technology
Applied Optics, 2004
A simple geometry optical sensor based on porous silicon technology is theoretically and experimentally studied. We expose some porous silicon optical microcavities with different porous structures to several substances of environmental interest: Very large red shifts in the single transmission peak in the reflectivity spectrum due to changes in the average refractive index are observed. The phenomenon can be ascribed to capillary condensation of vapor phases in the silicon pores. We numerically compute the peak shifts as a function of the liquid volume fraction condensed into the stack by using the Bruggeman theory. The results presented are promising for vapor and liquid detection and identification.
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.