Production and characterization of zinc oxide gas sensor

Semiconductor gas sensors are widely used in many areas from indoor and outdoor air quality determination to the detection of flammable or toxic gases. Zinc oxide-based gas sensors stand out among metal oxide gas sensors due to their fast response, low detection limit, high selectivity, and reliable performance. When energy efficiency and production costs are considered, gas sensors produced with microfabrication methods display great advantages. In these sensors, which are obtained based on the principle of changing the electrical resistance as a result of the active material adsorbing oxygen. The structure and the dimensions of the sensor materials, as well as the active microstructures that can be fit into the minimum area with the sensor design, are the main factors effecting the sensor efficiency. In this study, carbon monoxide detection performances of zinc oxide-based semiconductor gas sensors, which were produced by microfabrication methods with different electrode distances and designs under the same square micrometer area, were performed. As the active material, zinc oxide thin film was coated on a passivated silicon substrate by DC sputtering method. SEM, EDS, Ellipsometer, and XRD characterization techniques were performed to analyze the ZnO thin films. For electrical connection, gold on chromium electrodes are designed in circular, parallel, and square designs within 600x600 micrometer square and shaped by photolithography method. The effects of the distance between the electrodes and the designs were on detection rate and saturation time were investigated by electrical measurements under a carbon monoxide atmosphere. The lowest resistance and the fastest saturation time were obtained by the sensors which has 2-micron electrode widths and the electrode gaps.