Analytical model of a SAW gas sensor

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.

Analysis of Non-Steady Stage in SAW Gas Sensors with Semiconducting Sensor Layers

“…Figures 6-9 present exemplary results of the analysis in unsteady state concerning the sensor layer of WO 3 . The chosen representative gas was hydrogen, the properties of which have been investigated comprehensively in [3][4][5][6][7]. As can be seen in Fig.…”

“…Of no less importance is also the matching of a mathematical model to the achieved experimental results. These papers suggest a theoretical model as well as numerical analyses of a gas sensor of surface acoustic wave (SAW) type [1][2][3][4][5][6][7][8][9][10], in its steady state. As the phenomenon of the acoustoelectric effect depends in the set of a semiconducting layer and piezoelectric acoustic waveguide on the profile of the distribution of concentrations of the charge carriers in the sensor layer, it has been suggested to divide the sensor layer into thin sublayers, assuming a constant concentration of the carriers in these sublayers, alternating in each subsequent sublayer situated at different distances from the acoustic waveguide.…”

Numerical Analysis of Sensitivity of SAW Structure to the Effect of Toxic Gases

“…A stationary model (in the steady state) was supported by time dependences permitting research of dynamic characteristics of the SAW gas sensor (Urbanczyk, 2011a).…”

SAW sensor for detection of hydrocarbons. Numerical analysis and experimental results

“…The intensity interaction of the electric field with a sensing layer in a surface wave sensor depends not only on the electrical conductivity of the layer, but also on its distance from the piezoelectric waveguide. More details about the analytical model can be found in the paper by Hejczyk and Urbańczyk [4][5][6][7][8][9]. Analyzing the acoustoelectric effect in a SAW sensor, the sensing layer was assumed to consist of n-thin sublayers (Fig.…”

“…Using the transformation law for the n-th sublayer, it is possible to calculate the electrical admittance on the surface of the waveguide, which is "seen" by the surface wave. Then, the resultant of the admittance is used in Ingebrigtsen's formula [9][10][11] to determine the changes in the velocity of the surface wave resulting from the acoustoelectric interaction between the SAW and the sensor layer with a variable concentration of gas molecules in the y direction (in the depth of the layer). .…”