Improvement in real time detection and selectivity of phthalocyanine gas sensors dedicated to oxidizing pollutants evaluation

International audienceA sensor microsystem prototype, using copper phthalocyanine thin film as sensitive layer, and dedicated to ozone evaluation, was developed. The methodology implemented is based on cyclic sensor recalibrations by thermal cleaning of the sensitive membrane, and on pollutant concentration quantification according to the kinetics of sensor response. Results of laboratory experiments for various NO2 and O3 concentrations, in the range of 10–200 ppb, illustrate the selectivity of CuPc sensors towards ozone, obtained by our methodology. We have shown that ozone selectivity is especially improved for short time of exposure (few minutes) and for phthalocyanine layer maintained at low temperature (80 °C). For optimal conditions, our microsystem exhibits a threshold lower than 10 ppb, a resolution lower than 10 ppb, and good reproducibility of measurements. Performances obtained in real urban atmosphere are satisfying to ensure real time evaluation of ozone during several days. Long-term stability and the detection of NO2 by associating chemical filters to our microsystem will be also discussed

Réalisation et caractérisation de structures micro-électroniques à base de semiconducteur III-V(InP) (Application capteur de gaz)

CLERMONT FD-BCIU Sci.et Tech. (630142101) / SudocSudocFranceF

An original methodology of measurements for ozone detection in a mix (O3,NO2) with pseudo-schottky Pd-InP gas sensor

This article deals with Pseudo-Schottky diode consists of InP-p gas sensor with metallized layer of Palladium. In a first time, original results of carbon monoxide action (CO) on metallized layer are shown. It can be seen that Pseudo-Shottky diode submission to CO avoided the degradation of gas sensor parameters by ozone. Then an original methodology of measurements that takes avantages of gas sensor selectivity towards ozone, to follow in real time variations of concentration, is described

Management de l'identité de l'entreprise de services : la contribution des marques commerciales

International audienceCet article s'intéresse à la contribution des marques commerciales dans la gestion de l'identité de l'entreprise de services. Il a pour objectif de montrer que la marque commerciale peut aussi être considérée sous l'angle de la création d'une identité collective et utilisée comme outil de management interne

An original methodology dedicated to real-time detection of oxidizing gases based on pseudo-Schottky diode junction

International audienceThis original methodology has been developed to improve metrological parameters of a pseudo-Schottky diode toward oxidizing species (nitrogen dioxide and ozone). The pseudo-Schottky diode Pd/InP gas sensor ensured selectivity toward oxidizing gases and especially toward O3. This methodology, based on cyclic regenerations of the sensor palladium surface (CO reduction associated with thermal cleaning) and kinetics studies of sensor response, allows us to obtain reproducible measurements of NO2 and O3 concentrations in the range of 20–100 ppb. Our pseudo-Schottky sensor associated to this methodology exhibits low NO2 and O3 threshold values, high resolution, reproducible responses and real-time detection

Parameterized Source Separation For Delayed Spectroscopic Signals

International audienceThis paper addresses delayed (also known as anechoic) source separation when the source shape can be modeled by parameterized waveforms. An Alternating Least Squares (ALS) scheme is proposed to estimate the source shape parameters in a first step and both the mixing coefficients and the delays in a second step. For the challenging delay parameter estimation step, we adopt a strategy inspired by greedy algorithms. For highly correlated sources, the separation becomes ambiguous, and a second algorithm is proposed: a regularization term is added to favor slow delay evolution within each source. Results on synthetic and real data demonstrate the effectiveness of both algorithms compared to state-of-the-art methods for highly correlated Gaussian waveforms

H2, CO and high vacuum regeneration of ozone poisoned pseudo-Schottky Pd-InP based gas sensor

This article deals with pseudo-Schottky diode Pd–InP gas sensor. Catalytic activity of such palladium layer permits to measure very low concentrations of two powerful oxidizing gases, nitrogen dioxide (NO2) and ozone (O3), constituting main urban atmospheric pollution. After many O3 submissions, degradation of gas sensor characteristics (response time, recovery time and sensitivity) appears, probably due to ozone oxidation of palladium metallization. Different treatments (H2 reduction, CO reduction and high vacuum) were then tested to avoid degradation of sensor parameters. Initial response and recovery times of this sensor can be recovered by H2 reduction and high vacuum treatment of metallization layer after exposure to ozone. Moreover, results emphasize that these treatments improve sensor sensitivity. CO reduction will permit to have reproducible measurements of low NO2 and O3 concentrations

Studies of gas sensing, electrical and chemical properties of n-InP epitaxial surfaces

5-9 Septembre 200

Influence of technological process steps on the reproducibility, sensitivity and stability of InP based resistive gas sensors

This article deals with an InP based resistive gas sensor. Firstly, the InP gas sensor samples with good reproducibility were evaluated. The fabrication was obtained by a particular technological process. Secondly, the detection of NO2 was discussed. We compared the sensitivities, the stabilities and the influence of operating temperature between two different InP gas sensor samples