Using of SILD technology for surface modification of SnO 2 films for gas sensor applications
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Using of SILD technology for surface modification of SnO2 films for gas sensor applications G.Korotcenkov1, V.Macsanov1, Y.Boris1, V.Brinzari1, V.Tolstoy2, J.Schwank3, J.Morante4 1 Lab. of Microelectronics, Technical University of Moldova, Bld. Stefan cel Mare, 168, Chisinau, 2004, Rep. of Moldova; Tel.: (373)-2-247143; E-mail: [email protected] 2 Dept. of Chemistry, St. Petersburg State University, St.Petersburg, Russia; 3 Dept. of Chemical Engineering, University of Michigan, Ann Arbor, U.S.; 4 EME, Dept. d'Electronica, Universitat de Barcelona, Barcelona, Spain. ABSTRACT The possibilities of SILD (successive ionic layer deposition) technology for modification of surface properties of nano-scaled SnO2 films for gas sensor applications were studied and are discussed in this article. Samples of SnO2 with thickness ranging from 30-40 nm were deposited by spray pyrolysis from SnCl4-water solutions. Nano-clusters of Pd and Ag, deposited by the SILD method were applied for surface modification. PdCl2 and AgNO3 were used as precursors for Pd and Ag deposition on the SnO2 surface. It was found that the method of surface modification by SILD can be used for improving both the sensitivity and the rate of gas response of SnO2-based gas sensors to CO and H2. At the same time, the presence of Pd and Ag clusters on the surface of SnO2 depresses the gas response to ozone. INTRODUCTION Surface modification of metal oxides is becoming one of the most promising methods of optimization of gas sensing properties of conductometric solid state gas sensors [1-3]. In such sensors, the response signal is based on conductivity changes. Therefore, by using appropriate surface modifications, the adsorption and catalytic reaction characteristics on the sensor surface can be altered in such a way that gas-surface interactions lead to a maximum conductivity change of the base-metal-oxide matrix. For surface modification of metal oxides various surface additives may be used. Depending on gas type and support, these additives can act as a promoters, catalysts, or surface sites for adsorption of oxygen and detected gas with subsequent spillover of adsorbed species [13]. However recent research has shown that the most effective method of surface modification of metal oxides for gas sensor applications still remains the surface modification by noble metals such as Pd, Pt, Rh, and Ag [4-6]. The most important effects of noble metal addition are increased sensitivity and higher rates of response. Noble metal additives can also improve the selectivity and lower the temperature of maximum sensitivity. For noble metal incorporation into a metal oxide matrix, many different methods have already been demonstrated, such as bulk doping during scintillation, spray pyrolysis deposition, thermal evaporation, CVD, laser ablation, magnetron sputtering and so on [1-8]. With these methods it was possible to form on the surface of metal oxides clusters of noble metals with sizes from 0.1 to 8 nm.
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In this article we are presenting the results of
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