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Abstract:
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One of the main challenges in the development of metal-oxide gas sensors
is enhancement of selectivity to a particular gas. Currently, two general
approaches exist for enhancing the selective properties of sensors. The first one
is aimed at preparing a material that is specifically sensitive to one compound
and has low or zero cross-sensitivity to other compounds that may be present in
the working atmosphere. To do this, the optimal temperature, doping elements,
and their concentrations are investigated. Nonetheless, it is usually very difficult
to achieve an absolutely selective metal oxide gas sensor in practice. Another
approach is based on the preparation of materials for discrimination between
several analyte in a mixture. It is impossible to do this by using one sensor
signal. Therefore, it is usually done either by modulation of sensor temperature
or by using sensor arrays.
The present work focus on the characterization of n-type semiconducting
metal oxides like Tungsten oxide (WO3), Zinc Oxide (ZnO) and Indium oxide
(In2O3) for the gas sensing purpose. For the purpose of gas sensing thick as well
as thin films were fabricated. Two different gases, NO2 and H2S gases were
selected in order to study the gas sensing behaviour of these metal oxides. To
study the problem associated with selectivity the metal oxides were doped with
metals and the gas sensing characteristics were investigated.
The present thesis is entitled “Development of semiconductor metal oxide
gas sensors for the detection of NO2 and H2S gases” and consists of six chapters. |