Divya Haridas

Enhanced LPG response characteristics of SnO 2 thin film based sensors loaded with Pt clusters

In the present study, rf sputtered SnO2 thin films (90 nm thick) loaded with clusters of ultra-thin (8 nm) metal catalysts (Pt, Ag, Ni, Pb, Al, Pd) are investigated for LPG detection. It is noted that SnO2 film loaded with Pt catalyst clusters exhibits enhanced response (~ 750) to 200 ppm of LPG at a relatively low operating temperature (210degC) with a fast response time of 100s. Variation of thickness of Pt clusters in the nanoscale range (2 to 20 nm) is seen to significantly influence the sensor response characteristics. Enhanced performance is observed for SnO2 thin films loaded with 10 nm thick platinum clusters that exhibited a high response (~ 5 times 103) at an operating temperature of 220degC. Preliminary results indicate the potential application of prepared sensor structure of Pt clusters (10 nm)/SnO2 (90 nm)/IDE/glass substrate for efficient detection of LPG at relatively low temperature.

Enhanced response of SnO2 based thin film sensors towards methane gas due to the collective efforts of catalytic activity and photo-activation phenomenon

Detection of methane is always a great cause of concern for safety productions in mines and chemical factories. The present study investigates the twin effect of UV illumination and catalytic activity on methane sensing characteristics of SnO2 sensors. The sensitivity and selectivity of pure SnO2 thin film sensors are improved by loading it with Pd catalyst clusters (8 nm). Further, optimizing the thickness of Pd clusters leads to an enhanced sensing response of 97% to 99% over a wider temperature range (160°C to 240°C) for 10 nm thick Pd clusters. The room temperature response of SnO2-Pd (10 nm) sensor increases to 99.7% under UV illumination (which was around 0.6% at room temperature under no illumination) which is attributed to the efficient catalytic dissociation of methane molecules besides the spillover process at room temperature. The present study therefore investigates the effect of UV illumination on methane sensing characteristics of SnO2 sensors loaded with Pd clusters. Results indicate the possibility of utilizing the sensor structure with novel dispersal of Pd catalyst clusters on SnO2 film surface for efficient detection of methane at room temperature under the illumination of UV radiations.

Enhanced oxygen adsorption activity by CuO catalyst clusters on SnO 2 thin film based sensors

Resistance characteristics of thin film sensors based on uncoated SnO₂, SnO₂ with CuO overlayer and SnO₂ with CuO dotted clusters are compared in three different backgrounds of air, oxygen and vacuum. Measurements for the three sensor configurations are carried out as a function of temperature. The novel dispersal method of CuO catalyst in the form of dotted clusters is seen to enhance the oxygen adsorption activity on surface of SnO₂ thin film sensors. Conversion of molecular oxygen (O₂ ^-) to atomic oxygen (O^-) is shown to reduce the concentration of charge carriers in the conduction band of SnO₂ film. Co-existence of a greater amount of adsorbed oxygen on the SnO₂ film surface in conjunction with modulation of the space-charge region at the CuO-SnO₂ interface are attributed to influence the resistance of the sensor structures under reducing gas.

Fabrication of SnO 2 thin film based electronic nose for industrial environment

Nowadays e-nose is attracting the attention of many researchers due to its wide spread applications. The most important application falls in the category where human beings cannot afford to risk smelling toxic gases. Other important applications are continuous monitoring of pollutant and explosive gases, in oil and natural gas exploration, possible predictions of volcanic eruptions, medical applications, etc [1]. The fast paced technology has helped develop sophisticated devices that have led to miniaturization of electronic nose with advanced capabilities. This work reports on the performance of an array of four different sensor structures, using tin oxide as the base material, developed in order to detect (200 ppm) of LPG, methane, ammonia and H2S. The array, developed is composed of SnO2 thin films loaded with nanoclusters of four different catalysts namely Platinum, Palladium, Silver and Copper oxide by sputtering or evaporation technique. A good classification, success rate and prediction have been achieved for different target gases.

1.4.4 Analysis of industrial and domestic gases by means of electronic nose

In the present study a novel hybrid gas sensor array (E-Nose) composed of SnO2 thin film loaded with different catalyst clusters for sensitive gas discrimination followed by pattern recognition approach is demonstrated. An array of hybrid sensors (SnO2-Pt-custers, SnO2-Pd-clusters, SnO2-Ag-clusters, SnO2-CuO-clusters) operated at fixed temperatures have been developed for effective discrimination of target gases (LPG, Methane, Ammonia and H2S). Radar plots and Principal component analysis of the generated patterns of E-Nose showed great discrimination of the target gases. Principal component analysis of the sensing results showed great discrimination of target gases and an array of six sensors are proposed operating at lower temperature (60 o C or 140 o C) for realization of hybrid