Preparation And Sensing Property Of Nano-crystalline SnO₂ Thin Films Doped With In And Sb

Sensing technology is an important component part of modern science and technology. It is playing an increasingly important role in the development of national economy and science and technology. Along with economic and technological development of the industry in the areas, gas sensors are set higher and newer requirements, so vigorously developing the gas sensing technology is imperative. H₂S is a kind of extremely toxic gas, which is widespread in the oil and chemical production process. So it is urgent to develop sensors to detect trace H₂S gas.SnO₂ as sensitive material has been widely used.In this paper SnO₂ nano-membranes have been prepared by sol-gel dip-coating method using cheap inorganic salts and ethanol as raw materials. Sb ions are doped to decrease the thin-film's resistant, In-doping is to enhance the selectivity and sensitivity to H₂S and reduce operating temperature. And a systemic research is made to find out the relationship between preparation parameters such as In-doping, coating level and annealing temperature and film's properties like elemental morphology, grain size and gas sensing properties, etc. The results are below:The experimental results of sol component show: the best indium doping content is 4at%, with which the thin-film has lower operating temperature 165℃and the highest sensitivity that is 17.8 to 82.2 ppm H₂S.The experimental results of the fabrication process show: the best coating times is 7 and the best annealing temperature is 600℃, with which the thin-film has the most notable changes with the H₂S concentration. From the SEM images, we can find out the thin-film is more compact and has more uniform grain distribution. Analyzing the XRD patterns, we find the thin-film is composed of nano-crystalline polycrystalline. According to the Scherrer formula, grain size is calculated about 20.6 nm.SnO₂ thin-film is prepared by the best preparation parameters and its gas sensing properties are tested: the film's best operating temperature is 165℃. In this temperature the film's sensitivity to 137 ppm H₂S reaches 26.3, and also has good sensitivity to lower concentration which is 2.5 to 2.74 ppm H₂S. Furthermore, the response and recovery time are both short that is 8 s and 22 s respectively.