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Synthesis of fast response, highly sensitive and selective Ni:ZnO based NO<sub>2</sub> sensor
Ganbavle, V.V.,Inamdar, S.I.,Agawane, G.L.,Kim, J.H.,Rajpure, K.Y. Elsevier 2016 CHEMICAL ENGINEERING JOURNAL -LAUSANNE- Vol.286 No.-
The use of metal oxide semiconductor (MOS) gas sensors is limited due to lack of selectivity and high operating temperature. The aim of present investigation is to enhance gas response and sensitivity of the zinc oxide (ZnO) based thin film sensor towards nitrogen dioxide (NO<SUB>2</SUB>) by Ni doping. The achieved sensitivity is around 4.2%/ppm at moderate operating temperature of 200<SUP>o</SUP>C. The gas response of 108% and 482% is observed at 200<SUP>o</SUP>C operating temperature, towards 5ppm and 100ppm NO<SUB>2</SUB>, respectively. Ni doping increased the NO<SUB>2</SUB> response and reduced the lower detection limit of NO<SUB>2</SUB> to 5ppm which is much lower than the emergency exposure limit (20ppm). The hybrid structure of nanograined rods and hexagonal flakes are observed which enhanced gas response. The gas response dependence on various physical properties and chemical composition of the sensor is also studied. The response and recovery time of 1.5 atomic percentage (at%) Ni doped ZnO thin film sensor is 11 and 123s, respectively. The response of the sensor is reproducible and it has negligible cross sensitivity for other interfering gases such as CO<SUB>2</SUB>, SO<SUB>2</SUB>, H<SUB>2</SUB>S, NH<SUB>3</SUB>, LPG, methanol, ethanol, and acetone.
V.V. Ganbavle,S.V. Mohite,김진혁,K.Y. Rajpure 한국물리학회 2015 Current Applied Physics Vol.15 No.2
Sub-stoichiometric tungsten trioxide (WO3) thin films are deposited onto the glass substrates by spray pyrolysis technique using ammonium metatungstate. Effect of solution concentration on structural, morphological, optical, electrical and NO2 sensing properties of WO3 thin films is studied. Films are polycrystalline with monoclinic crystal structure and sub-stoichiometric as observed form the XRD and XPS studies, respectively. The SEM and AFM images show micro grained structure and surface roughness increases with increase in solution concentration. The PL studies revealed that the majority of the defects are the oxygen vacancies. From XPS and PL studies it is observed that, oxygen vacancies decrease with increase in solution concentration. The dielectric constant of the films as a function of frequency is in concurrence with resistivity measurements. Films show reproducible and reversible gas response at various operating temperatures and gas concentrations. Highest sensor response (38%) towards 200 ppm NO2 concentration is observed for the film with 15 mM solution concentration at moderate operating temperature (200 ℃). Pd sensitization enhanced gas response to 68% and improved kinetics of the sensor. Films are highly selective towards NO2 as compared with the various gases such as SO2, LPG, NH3 and H2S.