Studies on Spray Deposited SnO 2 , Pd:SnO 2 and F:SnO 2 Thin Films for Gas Sensor Applications
Abstract:Undoped tin oxide (TO), palladium-doped tin oxide (PTO) and fluorine-doped tin oxide (FTO) thin films have been prepared by spray pyrolysis method, under optimized conditions. Transmission measurement of the TO, PTO and FTO films have been studied in the UV-Visible region. Band gap energy evaluated from the spectral data lies between 3.15 eV and 3.8 eV. The X-ray diffraction analysis of the films confirms a polycrystalline, tetragonal rutile structure of tin oxide, with preferred orientation along the (101) plane. The lattice constants, a and c, were evaluated as 4.7256 Å and 3.1768 Å. The average grain size lies between 470 nm and 850 nm and its variation as a function of annealing temperature have been studied and reported. The AFM micrographs of the films reveal smooth and uniform surface pattern without any dark pits, pinholes and micro-cracks. The sheet resistance (R) and electrical resistivity ( ? ) of the films under ambient condition and CO gas atmosphere have been studied at different operating temperatures, in a specially designed sensor test rig setup. From the resistance measurement, response and recovery characteristics, detection sensitivity and optimum operating temperature of the as-coated TO, FTO and PTO films towards CO gas have been investigated and the results are discussed. Studies show a maximum detection sensitivity of 13.6% with a minimum response time of 110 sec. for the PTO thin films, at the operating temperature of 350°C.
Document Type: Research Article
Affiliations: 1: Department of Physics, Thiagarajar College of Engineering, Madurai, Tamilnadu State, India 2: Department of Physics, Government Girls Hr. Sec. School, Melur, Madurai, Tamilnadu State, India 3: Department of Mechatronics Engineering, Thiagarajar College of Engineering, Madurai, Tamilnadu State, India
Publication date: January 1, 2006