Title : Development and characterization of CuO and ZnO/CuO based CO gas sensors
Abstract:
Human population and industrialization are increasing in our society. So air pollution has become a serious issue in our environment. Carbon monoxide (CO) is one of the most toxic gases, which is colorless, tasteless and orderless. Metal oxides are very appealing materials due to their distinct physical and chemical properties, and are useful in a wide range of applications in today's digital society, including solar cells, microelectronics, optoelectronics, spintronic and various chemical sensors. Cupric oxide (CuO) is one of the important p-type metal oxides with a bandgap energy of 1.21 eV and is preferred for gas sensor fabrication [1]. CuO thin films of varying thickness ranging from 25 to 300 nm have been synthesized on alumina substrate by the thermal oxidation of Cu metal films deposited by vacuum evaporation method. The optimal oxidation conditions for the thermal oxidation of Cu films are 400 °C and 5 h, which convert Cu thin films to CuO via solid-state reaction [2]. From x-ray diffraction, CuO films are found to have polycrystalline nature with monoclinic crystal structure. The surface morphology of CuO evolves from coarse granular features to finer secondary grain formation with increasing CuO film thickness. The gas sensing characteristics of CuO films were examined using 106 ppm of CO gas at various measurement temperatures. It is found that the CuO film thickness of 200 nm exhibits a higher CO response of 52 % at 375 °C, where a minimum response/recovery time of 3.9 min./5.7 min was observed at 400 °C. Again ZnO/CuO heterostructure improved the sensing properties, which can detect at a lower temperature of 150
°C and maximum a CO response of 180 % was achieved at 375 °C. The fast and selective CO detection at low ppm levels was observed in ZnO/CuO heterostructure. The experimental conditions, the critical change in surface morphology and CO characteristics of CuO and ZnO/CuO structures will be discussed in detail.
Audience Take Away :
- Audience will get knowledge about the current situation and the importance to develop portable gas sensors.
- Prepared ZnO/CuO heterostructure gives importance to improving the sensing properties of the sensor device.
- The fabrication process of a heterostructure sensor device and study of sensing characteristics is very simple, which can help other faculty to improve the properformance
