Analytical Model Of A SAW Gas Sensor
Author(s)
M. Urbańczyk
Abstract
SAW gas sensors are attractive because of their remarkable sensitivity due to
changes of the boundary conditions (mechanical and electrical in the
acoustoelectric effect) propagating of the Rayleigh wave, introduced by the
interaction of a thin chemically active sensor film with gas molecules. This
unusual sensitivity results from the fact that most of the acoustic wave energy is
concentrated near the waveguide surface within approximately one or two
wavelengths. In the paper a new theoretical model of analysing a SAW gas
sensor is presented. The effect of SAW velocity changes depends on the profile
concentration of diffused gas molecules in the porous sensor film. Basing on
these analytical results, the sensor structure can be optimized. Some numerical
results are shown.
Keywords: gas sensor, SAW, acoustoelectric effect, Knudsen’s diffusion in
porous film, numerical modelling.
1 Introduction
A very interesting feature of SAW sensors is the fact that a layered sensor
structure on a piezoelectric substrate provides new possibilities of detecting gas
making use of the acoustoelectric coupling between the Rayleigh waves and the
free charge carriers in the semiconductor sensor layer. Using a configuration
with a dual delay line and an adequately chosen active layer, a sensor with a high
sensitivity and good temperature stability can be designed [1, 2]. SAW gas
sensors are attractive because of their remarkable sensitivity due to changes of
the boundary conditions of propagating the surface wave. This unusual
sensitivity results from the simple fact that most of the acoustic wave energy is
concentrated near the crystal surface within approximately one or two
wavelengths.
Keywords
gas sensor, SAW, acoustoelectric effect, Knudsen’s diffusion in
porous film, numerical modelling
Related Book
Other papers in this volume
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