Research Of Formaldehyde Gas Sensing Properties And Modification Based On NiO Thin Films

Metal oxide semiconductor(MOS) gas sensors are the most popular among all the detective methods. Because of their high sensitivity, short response and recover time, low cost, simplicity and compatibility with modern electronic devices, MOS gas sensor are the most attractive in the next generation of gas sensors. Recently, p type semiconductor which has high stability, good selectivity and some catalytic characteristic attracts lots of attentions. According to above consideration, this dissertation is focused on the investigation of formaldehyde gas sensing properties and modification based on Ni O thin films which is a p type semiconductor with high stability. The specific contents are as follows.(1) Effects of Oxygen partial pressure, applied bias and the thickness of films on the crystallinity, surface morphology and hanging keys of Ni O thin films which are deposited on the Si substrate by radio frequency magnetron sputtering are studied. Then Ni O thin films are deposited on Ti interdigital electrodes to achieve the HCHO gas sensor. And the gas sensing properties of Ni O for HCHO are tested. Results show that the Ni O thin films with small grain size, higher surface roughness and(111) diffraction peak exhibit higher gas sensing properties for HCHO.(2) The influence of doping to the gas sensing properties of Ni O is studied. Crystal structure, surface morphology and gas sensing properties to HCHO is characterized. Result shows that crystal structure and grain size have been changed by doping with Zn,Cu in Ni O thi films, g Gas sensing results show that the sensitivity for formaldehyde of Zn-doped Ni O, Cu-doped Ni O and un-doped Ni O is 0.39/ppm, 0.11/ppm and 0.08/ppm, respectively.(3)The influence of decoration that is made by different thickness of Zn O to the gas sensing properties of Ni O is studied. Results show that the optimal thickness of Zn O which is decorated on the surface of Ni O is achieved. And the gas sening properties of Ni O thin films are determined by the presence of Zn O and the uncovered Ni O surface.