Effect of Dispersal of Pd Nanocatalysts on H 2 Sensing Response of SnO 2 Thin Film Based Gas Sensor
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Effect of Dispersal of Pd Nanocatalysts on H2 Sensing Response of SnO2 Thin Film Based Gas Sensor Manish Kumar Verma1, Neha Batra1, Monika Tomar2, and Vinay Gupta1 1 Department of Physics and Astrophysics, University of Delhi, Delhi, 110007, INDIA. 2 Physics Department, Miranda House, University of Delhi, Delhi, 110007, INDIA. ABSTRACT SnO2 based sensor structures prepared by rf magnetron sputtering technique have been studied for detecting H2 gas. Pd catalyst was integrated onto the SnO2 thin film in the form of clusters and nano-particles to obtain enhanced sensing response characteristics. The prepared sensor structures have been studied over a temperature range of 50-250°C for sensing response towards 500 ppm H2 gas. The sensor with Pd catalyst dispersed in the form of nanoparticles was found to exhibit an enhanced sensing response of 1.9×103 at a relatively low operating temperature of 150°C with a fast response time of 2 s and recovery time of 65 s towards 500 ppm H2 gas. The origin of enhanced sensing response is identified in the light of the enhanced spill over of H2 gas molecules on the uncovered surface of SnO2 thin film. INTRODUCTION Recently there has been a lot of interest in hydrogen sensors, due to it being the prospective fuel of future. Hydrogen is a colourless, explosive, and extremely flammable gas having low minimum ignition energy (0.017 mJ), high heat of combustion (142 kJ/g H2) and wide flammable range (4í75%), as well as a high burning velocity, detonation sensitivity and an ignition temperature of 560°C. Hydrogen gas is important in the synthesis of ammonia and methanol, the hydration of hydrocarbons, the desulphurization of petroleum products and the production of rocket fuels, in metallurgical processes etc [1-3]. Being an explosive, colourless and odourless gas, hydrogen cannot be detected by human senses. Therefore, detection of hydrogen at low concentration is very essential to prevent disaster. Semiconducting tin oxide (SnO2) thin films are the most popular amongst the various semiconductor materials used for H2 gas sensing because of their capability of adsorption and desorption of oxygen from its surface. However, SnO2 based gas sensors lack the selectivity and give poor response which is being improved by use of metal and metal oxide catalysts. Different metal and metal oxides have been integrated with sensing SnO2 thin film for improvement in response and selectivity. Pd is the most widely used catalyst to improve selectivity towards H2 due to its strong affinity towards H2. Film morphology and integration of suitable catalyst along with the dispersal mechanism plays major role in the enhancement of sensing response characteristics. In the present work, Pd catalyst has been integrated with SnO2 thin film in the form of clusters and nanoparticles dispersed over the surface. The fabricated sensor has been studied for sensing response towards 500 ppm H2 gas. The effect of way of dispersal has been studied on the sensor response towards 500 ppm H2 gas.
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EXPERIMENTAL SnO2 thin fi
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