Cycled-growth and transport modelling of ZnO nanowires network towards low-temperature gas sensing

Conductometric metal-oxide gas sensors are widely used today due to their high sensitivity, but their integration into portable devices requires to find solutions for small, low-power, fast and cheap devices. Metal-oxide nanostructures, such as nanowires, are promising due to their large surface over volume ratio and reduced sizes, enhancing the sensitivity, response time and power consumption. Moreover, they can be synthetized in large-scale liquid phase methods and simply deposited as nanowire networks onto contacts, thus offering low-cost integration solutions. However, reproducible and reliable devices still require a full mastering of the fabrication methods and understanding of their influence on the conduction mechanism, which impact directly the sensitivity of the final sensor. In this thesis, we investigate an original metal oxide based gas-sensing device that integrates nanostructured ZnO nanowires-based network, allowing a low-power consumption and the integration into sensors’ arrays. These devices have ultimately the potential to improve the sensor's characteristics as sensitivity and selectivity for Semi- Volatile Organic Compounds (SVOC) for the real-time, qualitative and quantitative control of contamination. Moreover, this system may allow a local Joule heating to tailor the surface reaction, thus creating a heater-free device. The fabrication of this sensor requires the growth of size-controlled ZnO nanowires using standard nanotechnology techniques (liquid- phase synthesis). The controlled ZnO nanowires will allow us to propose an accurate conduction model for a uniform network-based thin film. The proposed conduction model and the sensor electronic performance is correlated, allowing the determination of its physical parameters which have never been discussed in previous reports.(FSA - Sciences de l'ingénieur) -- UCL, 201