Surface Passivation Effect on CO2 Sensitivity of Spray Pyrolysis Deposited Pd-F: SnO2 Thin Film Gas Sensor
Advances in Materials
Volume 3, Issue 5, October 2014, Pages: 38-44
Received: Sep. 12, 2014;
Accepted: Sep. 27, 2014;
Published: Oct. 10, 2014
Views 3142 Downloads 318
Patrick Mwinzi Mwathe, Department of Physics, Kenyatta University, Nairobi, Kenya; Department of Physics, University of Nairobi, Nairobi, Kenya
Robinson Musembi, Department of Physics, University of Nairobi, Nairobi, Kenya
Mathew Munji, Department of Physics, Kenyatta University, Nairobi, Kenya
Benjamin Odari, Department of Physics, University of Nairobi, Nairobi, Kenya
Lawrence Munguti, Department of Physics, Kenyatta University, Nairobi, Kenya;Department of Physics, University of Nairobi, Nairobi, Kenya
Alex Alfred Ntilakigwa, Department of Physics, University of Nairobi, Nairobi, Kenya; Faculty of Science Technology and Environmental Studies, Open University of Tanzania, Dar es Salaam, Tanzania
Julius Mwabora, Department of Physics, University of Nairobi, Nairobi, Kenya
Walter Njoroge, Department of Physics, Kenyatta University, Nairobi, Kenya
Bernard Aduda, Department of Physics, University of Nairobi, Nairobi, Kenya
Boniface Muthoka, Department of Physics, University of Nairobi, Nairobi, Kenya
Different thin films samples made of SnO2, F:SnO2, Pd: SnO2 and and co-doped Pd-F: SnO2 were deposited at a substrate temperature of 450oC using optimized doping concentrations of F and Pd, thereafter the samples were annealed and passivated in a tube furnace at 450oC. Optical and electrical methods were used in characterizing the thin film samples: The band gap energy for all samples was extracted from optical data using a proprietary software, Scout™ 98. The calculated band gap energy were found to be 4.1135eV for Pd:SnO2 and 3.8014eV for F:SnO2 being the highest and the lowest calculated band gap energies, respectively. The wide band gap energy has been attributed to the incorporation of Pd ions in crystal lattice of SnO2 thin film for Pd:SnO2 while for F:SnO2 has been due to incorporation of F- ions in the crystal lattice of SnO2 which gives rise to donor levels in the SnO2 band gap. This causes the conduction band to lengthen resulting to a reduction in the band gap energy value. The electrical resistivity was done by measuring the sheet resistance of the SnO2, Pd:SnO2, F:SnO2 and Pd-F:SnO2 thin films. The undoped SnO2 thin film had the highest sheet resistivity of 0.5992 Ωcm while F:SnO2 had the lowest sheet resistivity of 0.0075 Ωcm. The low resistivity of F:SnO2 results from substitution incorporation of F- ions in the crystal lattice of SnO2 thin films, instead of O- ions which lead to an increase in free carrier concentration. The Pd-F:SnO2 gas sensor device was tested for CO2 gas sensing ability using a lab assembled gas sensing unit. The performance of the gas sensor device was observed that: the as prepared device was more sensitive to CO2 gas than those subjected to annealing and passivation. The decrease in the sensitivity of the annealed Pd-F: SnO2 gas sensor is attributed to decrease in grain boundary potential resulting from grain growth. This causes a decrement in adsorption properties of CO- and O- species by the annealed Pd-F: SnO2 thin film. The sensitivity of passivated Pd-F: SnO2 gas sensor was found to be the lowest. The low sensitivity is due to the effects of nitration and decrement in grain boundary potential resulting from grain growth, nevertheless, the sensitivity of the passivated Pd-F: SnO2 thin film was found to be within the range for gas sensing applications.
Patrick Mwinzi Mwathe,
Alex Alfred Ntilakigwa,
Surface Passivation Effect on CO2 Sensitivity of Spray Pyrolysis Deposited Pd-F: SnO2 Thin Film Gas Sensor, Advances in Materials.
Vol. 3, No. 5,
2014, pp. 38-44.
Sun, B., Guangzhong, X., Jiang, Y and Xian, L. Comparative CO2-Sensing Characteristic Studies of Starch Thin Film Sensors. Journal of Energy Procedia, vol 12, pp 726 – 732, 2011.
Bochenkov, V. E and Sergeev, G. B. Preparation and chemiresistive properties of nanostructured materials. Advances in Colloid and Interface Science, Russia, vol 116, pp 245-254, 2005.
Salehi, H., Aryadoust, M., and Farbod, M. “Electronic and Structural Properties of Tin Dioxide in Cubic Phase”. Iranian Journal of Science & Technology, Trans. A, vol 34, (A2), pp 131-138, 2010.
Shamala, K.S., Murthy, L.C.S and Rao, K.N. “Studies on tin oxide films prepared by electron beam evaporation and spray pyrolysis methods” Bull. Mater. Sci. vol 27, pp295-301, 2004.
Subramanian, N.S, Santhi, B, Sundareswaran, S, Venkatakrishnan, K.S. “Studies on Spray Deposited SnO2, Pd:SnO2 and F:SnO2 Thin Films for Gas Sensor Applications”, Synthesis and Reactivity in Inorganic. Metal-Organic, and Nano-Metal Chemistry,vol 36,pp 131-135, 2006.
Rakhshani, E.A., Makdisi, Y and Ramazaniyan, A.H. “Electronic and optical properties of fluorine-doped tin oxide films”. J. Applied Phys. vol 83, pp 1049-1057, 1998.
Mohammad, T.M. “Performance and characteristics of Al-PbS/SnO2: F selective coating system for photothermal energy conversion”. Solar Energy Mater. Vol 20,pp 297-305, 1990.
Boshta, M., Mahmud, A. and Sayed, M. H. Characterization of sprayed SnO2: Pd thin films for gas sensing applications. Journal of Ovonic Research, vol 6, pp 93 – 98, 2010.
Odari, B.V., Mageto, M., Musembi, R., Othieno, H., Gaitho, F., and Muramba, V. “Optical and Electrical Properties of Pd Doped SnO2 Thin Films Deposited by Spray Pyrolysis”. Australian Journal of Basic and applied Sciences, vol 7(2), pp 89-98, 2013.
Adamyan, A.Z., Adamyan, Z.N., Aroutiounian, V.M., Schietbaum, K.D and Han, S-D. “Improvement and Stabilization of Thin – Film Hydrogen Sensors Parameters”. Armenian Journal of Physics, vol 2, pp 200-212, 2009.
Bochenkov, V. E and Sergeev, G. B. Sensitivity, Selectivity, and Stability of Gas-Sensitive Metal-Oxide Nanostructures and their Applications: American Scientific Publishers, Russia, vol 3, pp 31-52, 2010.
Miller, T.A., Bakrania, S.D., Perez, C and Woondridge. Nanostructured Tin Dioxide Materials for Gas Sensor Applications. American Scientific Publishers, Michigan USA, pp 1-24, 2006.
Vaezi M.R. Effects of surface modification on the recovery time and stability of nano structured tin oxide thick films gas sensors. International Journal of electronics Transactions B: Applications, vol 20, pp 1-8, 2007.
Jebbari, N., Kamoun, N and Bennaceur, R. “Effect of SnCl4 concentration on F: SnO2, deposited by chemical spray pyrolysis”. In the proceedings of International Renewable Energy Congress, Souse, Tunisia, vol 2, pp 276-279, 2010.
Mwathe, P.M., Musembi, R., Munji, M., Odari, B., Munguti, L., Ntilakigwa, A, A., Nguu, J., Aduda, B., Muthoka, B. Influence of Surface Passivation on Optical Properties of Spray Pyrolysis Deposited Pd-F:SnO2. International Journal of Materials Science and Applications. Vol. 3, No. 5, pp 137-142, 2014.
Daniya M. Mukhamedshina and Nurzhan B. Beisenkhanov Influence of Crystallization on the Properties of SnO2 Thin Films, Advances in Crystallization Processes, Dr. Yitzhak Mastai (Ed.), InTech Europe, pp 221-258, 2012.
Baco, S., Chik, A and Tassin, F.Md. “Study on Optical Properties of Tin Oxide Thin Films at Different Annealing Temperatures”. Journal of Science and Technology, vol 4, pp 61-72, 2012.
Sandipan R, Gupta P.S. and Gurdeep S. “Electrical and Optical properties of sol-gel prepared Pd-doped SnO2 thin films: Effect of multiple layers and its use as room temperature methane gas sensor”, Journal of Ovonic Research,vol 6(1), pp 63-74, 2010.
Sa’nchez-Garcia, M., Maldonado, Castaneda, L., Silva- Gonzalez, R and Olvera, M.L. Characterization of SnO2:F Thin Films Deposited by Ultrasonic Spray Pyrolysis: Effect of Water Content in Solution and Substrate Temperature. Materials, Sciences and Applications, vol 3, pp 690-696, 2012.
Moure- Flores, F., Guillen – Gervauntes, A., Nieto-Zapeda, K.E., Quinones- Galvan, JG., Hernandez- Hernandez. A., Olvera, M.G and Melendez- Lira, M. “SnO2 Thin Films Deposited by RF Magnetron Sputtering: Effect of the SnF2 Amount in the Target on the Physical Properties”. Revista Mexicana de Fisica, vol 59, pp 335-338, 2013.
Yousaf, S.A and Ali, S. “The Effect of Fluorine Doping on Optoelectronic Properties of Tin-Dioxide (F:SnO2) Thin Films”. Journal of Natural Sciences and Mathematics, vol 48, pp 43-50, 2008.
Edgar Sotter. Development of a Thick Film Gas Sensor for Oxygen Detection at Trace Levels, PhD thesis, Xavier Vilanova, Tarragona Spain, 2006.
Batzill, M and Diebold U. The surface and materials science of tin oxide. Progress in Surface Science, vol 79, pp 47–154, 2005.
Mishra, R. L., Mishra, S.K and Prakash, S.G. “Optical and Gas Sensing Characteristics of Tin-Dioxide Nano-Crystalline Thin Films.” Journal of Ovonic Research, vol 5, pp77-85, 2009.
Desale, J.D., Shaikh, S., Siddique, F., Ghosh, A., Birajdar, R., Ghale, A and Sharma, R. Effect of Annealing on Structural and Optoelectronic Properties of Cds Thin Films Prepaered by SILAR Method. Advances in Applied Research, vol 2, pp 417-425, 2011.
Simo˜es, A.Z., Riccardi, C.S., Dos Santos, M.L., Gonza´ lez Garcia, F., Longo E and Varela J.A. Effect of annealing atmosphere on phase formation and electrical characteristics of bismuth ferrite thin films. Materials Research Bulletin, vol 44, pp 1747–1752, 2009.