Modeling of the conduction in a WO3 thin film as ozone sensor

Abstract In this paper we propose a model for ozone detection in atmospheric conditions. The sensitive layer material used in this study is tungsten oxide. The interaction between the semiconductor surface and the gases is approached by means of the adsorption theory described by Wolkenstein in order to determine the equilibrium state of the grains. The layer conductivity is then determined by computing the current flowing between the grains (in the spherical assumption) across the depletion layer induced by the adsorbed molecules and the semiconductor interaction. This calculation is performed using the “drift diffusion” equation set. We have first analyzed the oxygen adsorption effect, then the ozone adsorption one and finally, the combined action of the two mixed gases on the sensor layer. This model takes into account the fundamental mechanisms implied in the gas detection and the results obtained are in good agreement with the experimental results.

[1]  Daren J. Caruana,et al.  Modelling the response of a tungsten oxide semiconductor as a gas sensor for the measurement of ozone , 2002 .

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

[3]  Thomas J. McAvoy,et al.  Surface state trapping models for SnO2-based microhotplate sensors , 2001 .

[4]  David E. Williams,et al.  Tin dioxide gas sensors. Part 1.—Aspects of the surface chemistry revealed by electrical conductance variations , 1987 .

[5]  Vincenzo Guidi,et al.  AC measurements and modeling of WO3 thick film gas sensors , 2005 .

[6]  Helmut Geistlinger,et al.  Electron theory of thin-film gas sensors , 1993 .

[7]  N. Bârsan,et al.  In2O3 and MoO3–In2O3 thin film semiconductor sensors: interaction with NO2 and O3 , 1998 .

[8]  Atul Patel,et al.  An ab initio Hartree-Fock study of the cubic and tetragonal phases of bulk tungsten trioxide , 1996 .

[9]  V. Lantto,et al.  Electrical studies on the reactions of CO with different oxygen species on SnO2 surfaces , 1987 .

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

[11]  A. Berg,et al.  Ammonia sensors and their applications - a review , 2005 .

[12]  Ingemar Lundström,et al.  Approaches and mechanisms to solid state based sensing , 1996 .

[13]  R. Birringer,et al.  Numerical analysis of space charge layers and electrical conductivity in mesoscopic cerium oxide crystals , 2004 .

[14]  V. Lantto,et al.  Computational approaches to the chemical sensitivity of semiconducting tin dioxide , 1998 .

[15]  A. Rothschild,et al.  Numerical computation of chemisorption isotherms for device modeling of semiconductor gas sensors , 2003 .

[16]  T. Doll,et al.  A rate equation approach to the gas sensitivity of thin film metal oxide materials , 2005 .

[17]  S. K. Deb,et al.  Oxygen vacancy in cubic WO3 studied by first-principles pseudopotential calculation , 2003 .

[18]  Gabor Kiss,et al.  Study of oxide semiconductor sensor materials by selected methods , 2001 .

[19]  Conductivity of SnO2 thin films in the presence of surface adsorbed species , 2001 .

[20]  A. Rothschild,et al.  Sensing behavior of TiO2 thin films exposed to air at low temperatures , 2000 .

[21]  T. Wolkenstein,et al.  Electronic Processes on Semiconductor Surfaces during Chemisorption , 1991 .

[22]  Roderic L. Jones,et al.  An ozone monitoring instrument based on the tungsten trioxide (WO3) semiconductor , 2006 .

[23]  V. Brynzari,et al.  Simulation of thin film gas sensors kinetics , 1999 .

[24]  Khalifa Aguir,et al.  Thermal modelling of a WO3 ozone sensor response , 2005 .

[25]  Wu Xinghui,et al.  Electrical and gas-sensing properties of WO3 semiconductor material , 2001 .

[26]  Khalifa Aguir,et al.  Impedance spectroscopy on WO3 gas sensor , 2005 .

[27]  Libor Gajdošík.  The concentration measurement with SnO2 gas sensor operated in the dynamic regime , 2005 .