Tin Dioxide Nanodimensional Film Based H2 sensor
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0915-R06-26
Tin Dioxide Nanodimensional Film Based H2 sensor Serghei Dmitriev Department of Industrial and Applied Chemistry, Moldova State University, 60, A. Mateevici Str., Chisinau, MD-2009, Moldova ABSTRACT This paper presents results of an investigation aimed at the development of tin dioxide nanodimensional film gas sensors (NDFGS) with a high sensitivity to hydrogen. Specifics of the performed research depend upon an approach which combines using nanodimensional metal oxide film, as a gas-sensitive device, and group electron technology methods that allow both small and large-scale manufacturing of given NDFGS. The gas-sensitive nanodimensional film (NDF) has been prepared by a chemical spray pyrolysis method on both the ceramic substrate for study and optimization of electrophysical and gas sensitive characteristics and the “chip” of a gas sensor (GS) preliminarily produced through group electron technology. Films were deposited at temperatures in the interval 400-500oC from water solutions of the SnCl4.5H2O precursor. The thickness of the SnO2 films varied in the range of 40-80 nm. The study of the electrophysical characteristics of the obtained layers has shown that the y can exhibit an electrical resistance of 105-106 Ohm at the working temperatures of the gas sensor. Gas sensitivity was determined as the ratio of SnO2 film resistance in pure air and in the presence of gas impurity in atmosphere (S=Rgas/Rair). Values of R were determined through Van-der-Pauw method. X-ray and SEM investigation has allowed us to establishment a connection between processing parameters, nanostructure and gas sensitive characteristics of the films obtained using this method. Gas sensitivity (S) of the deposited undoped films amounts to 9-10 relative units per 100 ppm of hydrogen in air. Modifying the gas sensitive properties of tin dioxide NDF through bulk and surface doping with Pd increases hydrogen sensitivity up to almost 104 rel. units, for hydrogen concentrations down to 1 ppm and the maximum sensitivity is observed at reduced operarating temperatures (from 350oC in the case of undoped films to 150oC for Pd-doped NDF).
INTRODUCTION Metal oxide-based gas sensors (GS) positioned on the base of thin films have been widely applied in toxic (CO, NH3, SO2, etc.) and explosive (H2, CH4, C3H8, etc.) gas detection in the monitoring of environment pollution and the control of different industrial processes. Due to the reduction of power consumption and cost, it could be a possibility for further miniaturization and integration in microsystems for air quality monitoring [1,2]. In the majority of GS, SnO2 metal oxide semiconductor is used as the gas sensitive element. The change the surface conductivity of a material has been used to detect air pollutants in various studies in the literature [3,4].
SnO2 is characterized by high thermal and chemical resistivity and stability as well as sensitivity to a wide spectrum of gases; at the same time, it demonstrates very poor gas selectivity. Thus, obtaining high level of selectivity f
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