Enhanced response characteristics of SnO 2 thin film loaded with nanoscale catalytic clusters for Methane gas
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Enhanced response characteristics of SnO2 thin film loaded with nanoscale catalytic clusters for Methane gas
Divya Haridas1,2, Arijit Chowdhuri3, K. Sreenivas1 and Vinay Gupta1 Dept. of Physics and Astrophysics,University of Delhi, Delhi, India 2 Keshav Mahavidyalaya, Pitampura, University of Delhi, India 3 Acharya Narendra Dev College, Govindpuri, University of Delhi, India
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ABSTRACT In recent years, an increase in usage of methane gas in household and automobile industry has been observed. Detection of methane is always a great cause of concern for safety at home or automobile industries, productions in mines and chemical factories. This paper reports the response characteristics of rf-sputtered SnO2 thin films (90 nm thin) loaded with nanoscale catalytic clusters for detection of methane. Ultrathin (8 nm) metal and metal-oxide catalysts (Pt, Ag, Ni, Pd, Au, NiO, Au2O3) clusters are loaded over the surface SnO2 thin film. The SnO2-Pd cluster structure is found to exhibit an enhanced response (97.2%) for 200 ppm of methane at a relatively low operating temperature (220oC). The enhanced response is shown to be primarily due to the dominant roles played by both Fermi level energy control mechanism and spillover mechanism. INTRODUCTION Methane is found in environment, industrial and domestic areas. It is the main constituent of natural gas which is the fuel supplied to homes and industries. Natural gas is often released from the walls of coal mines and when unmonitored, it can accumulate resulting in dangerous explosions. Methane gas is highly volatile when mixed with air and can cause explosion due to inflammability. It has a lower explosion limit (LEL) of 4.9% and an upper explosion limit (UEL) of 15.4% [1]. Thus, detection of trace level of methane gas in the environment is very important to avoid any accidental explosion due to its leakage from automobiles. Continuous efforts are ongoing worldwide towards development of an efficient methane sensor that could work even at low temperatures. Among a variety of semiconducting metal oxides, tin oxide (SnO2) is the most preferred material for gas sensor application because of its enhanced ability to adsorb oxygen on its surface. Efforts are continuing towards the enhancement of sensing response of methane sensors along with the reduction in operating temperature either by fabricating good quality SnO2 thin films or by incorporating an appropriate catalyst in various manners [2]. However, few attempts have been made towards the study of the effect of various catalysts on the sensing response characteristics of SnO2 thin film for methane gas [3-6]. In the present work, we have loaded the surface of rf-sputtered SnO2 thin film with uniformly distributed ultrathin clusters of catalysts of
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different metals and their oxides for detection of methane gas. A significant improvement in the sensor response was observed using a structure consisting of palladium clusters on the surface of SnO2 thin film. The SnO2 sensor loaded with 8 nm thin Pd clusters exhibits a respons
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