The Fabrication And Study Of Fast-Recoverable Low-Energy Consuming Nanostructure Based Sensor

The key in the mechanistic description of gas sensing in chemiresistors based on semiconducting metal oxides is the oxygen atoms chemisorptive processes, ―oxygen ionosorption‖. Due to the strong electron affinity of oxygen, the electrons can be transferred to the chemisorbed oxygen and, consequently, there will be oxygen ions in the surface. However, the electron-stripping process, known as ionization, in principle, requires an elevated temperature environment about 200~400℃, which means the sensitivity or response of the metal-oxide-based gas sensor require a relatively high environmental temperature. How to improve the sensing performance at low temperature has been a research focus at recent years. Although the high sensitivity has been achieved, it is still critical to optimize the adsorption/desorption process at relatively low temperature. Low operating temperature and fast recovery process is a pair of contradictions which is uncompatible for the metal oxide based sensors. Our works focus on the gas-sensing device working at low-temperature with fast recovery time. Possible solutions to the existing major issue of gas sensors are explored.We aimed at environmental monitoring, and focus on metal oxides based gas sensors and F-P based interferometric sensors, both of which can detect the change of the ambient medium. The main contents and progress of the paper are shown belown:1) High quality copper oxide/tungsten oxide(CuO/WO3) heterostructured structure are prepared and demonstrated for gas detection at low-temperature. In the case of n type WO3 nanocubes doped with p type CuO particles, we found the gas sensing sensitivity is no longer dependent just on the oxygen ions concentration, which is different from the conventional surface-depletion model at the high temperature. The hybrid-based sensors have a high response up to ~2.7?105 at 60 °C to 4 ppm H2 S, and the detection limit can be down to 50 ppb. In order to realize fast recovery at low temperature, the testing circuit was restructured and an electric modulation pulse was employed. By this method, the recovery time is reduced to 65 s. This solution can be generalized to more metal oxide based sensors as an effective way to facilitate recovery process.2) Compared with traditional gas sensors which have fatal drawbacks like high operating temperature, serious background noises, and poor stability, our sensors show enormous advantages, such as low energy consuming, fast response/recovery process, and striking repeatability. We investigate the mechanism of the Fabry-Perot resonant cavity based sensors, study the sensing performance of the optic F-P refraction index sensor, and realize the ability to tune the operating wavelength from 0.2~2 ?m. Theory analysis and experimental results show that both resonance wavelength and resonance intensity are very sensitive to tiny change of incident angle. In order to solve the angle-dependent problem, we use metal pattern to substitute the uniformly deposited metal film. In addition, we explore the metal shell based local surface plasmon resonance model, providing a potential way to achieve angle-independent refraction index sensor.