Understanding the fundamental principles of metal oxide based gas sensors; the example of CO sensing with SnO2 sensors in the presence of humidity

This paper investigates the effect of water vapour in CO sensing by using Pd doped SnO2 sensors realized in thick film technology as an example of the basic understanding of sensing mechanisms applied to sensors. The results of phenomenological and spectroscopic measurement techniques, all of them obtained under working conditions for sensors, were combined with modelling in order to derive conclusions able to be generalized to the field of metal oxide based gas sensors. The techniques employed were: dc conductance, ac impedance spectroscopy, work function (by using the Kelvin probe method), catalytic conversion and diffuse reflectance infrared Fourier transform measurements. The most important conclusion is that the different parts of the sensor (sensing layer, electrodes, substrate) are all influencing the gas detection and their role has to be taken into consideration when one attempts to understand how a sensor works. (Some figures in this article are in colour only in the electronic version)

[1]  Isabel Sayago,et al.  Use of complex impedance spectroscopy in chemical sensor characterization , 1991 .

[2]  Udo Weimar,et al.  Investigation of CO/CH4 mixture measured with differently doped SnO2 sensors , 2001 .

[3]  János Mizsei,et al.  Resistivity and work function measurements on Pd-doped SnO2 sensor surface , 1983 .

[4]  K. Ihokura,et al.  The Stannic Oxide Gas SensorPrinciples and Applications , 1994 .

[5]  M. Vallet‐Regí,et al.  Capacitance effects and gaseous adsorption on pure and doped polycrystalline tin oxide , 1995 .

[6]  Koji Moriya,et al.  Combustion monitoring sensor using tin dioxide semiconductor , 1991 .

[7]  Meng Guangyao,et al.  Study on SnO2-Fe2O3 gas-sensing system by a.c. impedance technique , 1993 .

[8]  V. Lantto,et al.  The effect of microstructure on the height of potential energy barriers in porous tin dioxide gas sensors , 1988 .

[9]  N. Bârsan,et al.  Conduction Model of Metal Oxide Gas Sensors , 2001 .

[10]  Nicolae Barsan,et al.  DRIFT studies of thick film un-doped and Pd-doped SnO2 sensors: temperature changes effect and CO detection mechanism in the presence of water vapour , 2003 .

[11]  R. Ionescu,et al.  The mechanism of the interaction between CO and an SnO2 surface: the role of water vapour , 1993 .

[12]  Przemyslaw M. Szecowka,et al.  Simultaneous quantification of carbon monoxide and methane in humid air using a sensor array and an artificial neural network , 1997 .

[13]  Udo Weimar,et al.  Conductance, work function and catalytic activity of SnO2-based gas sensors , 1991 .

[14]  Udo Weimar,et al.  In situ diffuse reflectance infrared spectroscopy study of CO adsorption on SnO2 , 2001 .

[15]  W. Gőpel.  Chemisorption and charge transfer at ionic semiconductor surfaces: Implications in designing gas sensors , 1985 .

[16]  Wolfgang Göpel,et al.  SnO2 sensors: current status and future prospects☆ , 1995 .

[17]  David E. Williams.  Semiconducting oxides as gas-sensitive resistors , 1999 .

[18]  G. Martinelli,et al.  A study of the moisture effects on SnO2 thick films by sensitivity and permittivity measurements , 1995 .

[19]  János Mizsei,et al.  Simultaneous response of work function and resistivity of some SnO2-based samples to H2 and H2S , 1991 .

[20]  J. Kappler,et al.  Correlation between XPS, Raman and TEM measurements and the gas sensitivity of Pt and Pd doped SnO2 based gas sensors , 1998 .

[21]  A. Ovenston,et al.  Effect of frequency on the electrical characteristics of tin-antimony-oxide mixtures , 1994 .

[22]  Udo Weimar,et al.  Multicomponent gas analysis: An analytical chemistry approach applied to modified SnO2 sensors , 1990 .

[23]  B. Flietner,et al.  Dipole- and charge transfer contributions to the work function change of semiconducting thin films: experiment and theory , 1996 .

[24]  R. Ionescu,et al.  Role of water vapour in the interaction of SnO2 gas sensors with CO and CH4 , 1999 .

[25]  Udo Weimar,et al.  CO consumption of Pd doped SnO2 based sensors , 2001 .

[26]  J. Sinkkonen.  DC Conductivity of a Random Barrier Network , 1980 .

[27]  J. T. Ranney,et al.  The Surface Science of Metal Oxides , 1995 .

[28]  M. Egashira,et al.  Change of thermal desorption behaviour of adsorbed oxygen with water coadsorption on Ag+-doped tin(IV) oxide , 1981 .

[29]  N. Bârsan,et al.  High-Performance Gas Sensing of CO:  Comparative Tests for Semiconducting (SnO(2)-Based) and for Amperometric Gas Sensors. , 1999, Analytical chemistry.

[30]  S. Lenaerts,et al.  In-situ infrared and electrical characterization of tin dioxide gas sensors in nitrogen oxygen mixtures at temperatures up to 720-k , 1994 .

[31]  R. Ionescu,et al.  Time-dependence of the conductance of SnO2: Pt: Sb in atmospheres containing oxygen, carbon monoxide and water vapour I. Non-oscillatory behaviour , 1994 .

[32]  Noboru Yamazoe,et al.  Interactions of tin oxide surface with O2, H2O AND H2 , 1979 .