Properties of polycrystalline gas sensors based on d.c. and a.c. electrical measurements

Research Projects
Organizational Units
Journal Issue
Electrical properties of polycrystalline gas sensors are analyzed by d.c. and a.c. measurements. d.c. electrical conductivity values compared with those obtained by admittance spectroscopy methods help to obtain a detailed 'on line' analysis of conductivity-modulated gas sensors. The electrical behaviour of grain boundaries is obtained and a new design of sensors can be achieved by enhancing the activity of surface states in the detecting operation. A Schottky barrier model is used to explain the grain boundary action under the presence of surrounding gases. The height of this barrier is a function of gas concentration due to the trapping of excess charge generated by gas adsorption at the interface. A comparison between this dependence, and a plot of the real and imaginary components of the admittance versus frequency at different gas concentrations, provides information on the different parameters that play a role in the conduction mechanisms. These methods have been applied to the design of a CO sensor based on tin oxide films for domestic purposes, the characteristics of which are presented.
Copyright © 1992 Published by Elsevier B.V. Symposium B: New Materials, Physics & Technologies for Micronic Integrated Sensors The authors will like to thank COPRECI (FAGOR S. Cop.) Mondragón (Spain) for the finantial support in this research
Unesco subjects
[1] J.Werner. Electronic properties of grain boundaries. Polychrystalline semiconductors. Springer Verlag 1985 [2] G. Blatter & F. Greuter. Electrical properties of grain boundarics in presence of deep bulk. Polychrystalline semiconductors. Springer Verlag 1985 [3] C.H. Scager & G.E. Pike. App. Phys. letters 37 747 (1980) [4] J.W. Orton & M.J. Powell. Rep. on Progress Pbys. 43 (1980) 1263-1307. [5] S.M. Sze. Physics of semiconductor devices. 2nd ed. 1981. J. Wiley. [6] P.T. Moseley & B.C. Tofield. Solid State Gas Sensors. Adam Hilger 1987. [7] J. Agapito & J. Gutiérrez. IV Eurosensors Congress. Karlsrube 1990. Sensors & actuators. Special issue, may 1991. [8] J. Gutiérrez, J. Agapito & alt. IV Eurosensors Congress. Karlsrube 1990. Sensors & actuators. Special issue, may 1991.