Qiu Nan-wan

Powder Sputtered SnO2, ZnO Thin Film Gas Sensors

Powder sputtering method has the advantage of doping impurity stability. Some performances of SnO2, ZnO gas sensing thin film and the idea of designing gas sensor are introduced. The processing, techniques, chip structure and performance about two kinds of thin film gas sensors are given out. Simultaneously, we got two conclusions: the first one, metal oxide thin film sensor obtained by the powder sputtering method is likely to become popular goods in the field of gas sensors; the other one, ZnO thin film is another gas sensor basic material besides SnO2 that can be studied and developed. The key for ZnO thin film sensor is to choose the suitable substrate

Thermal-Power Consumption and Heat Transfer Coefficients in Micro-thin-film Gas Sensors

The thermal-power consumption is a important parameter of gas sensor. The temperature distribution of thin film gas sensor, temperature of metal guard, the dissipating heat of lead-wires and the regularity of sensors heat transfer coefficient varying with size of heat-transfer surface and working temperature was studied. The formula of thermal-power consumption of micro-thin-film gas sensors yielded in this paper, from which, the calculation results consisted with the experiment. Finally, some related problems were discussed

Experiment and Theory for the Thickness Effect of Nano Metal Oxide Gas Sensing Thin Film Dynamic Thickness Effect and Theory of Diffusion Reaction

The rule of characteristic time varies with film thickness, gas concentration is given by experiment results. The diffusion reaction model of conductance response for porous gas sensing thin film is proposed; with solution and non-dimensional analyze the reaction diffusion equation, the rule of character time can be yielded. Using the method of combination of theoretical and experimental, the surface adsorption exponent gamma and adsorbing energy Ea are discussed

Experiment and Theory for the Thickness Effect of Nano Metal Oxide Gas Sensing Thin Film The Thickness Effect and Mesoscopic Theory of Conductance Activity Energy

The characteristics of conductance activity energy of SnO2 thin film varies with film thickness l and grain size r0 are given by experiment results. The cross-section current formula of porous materials and the conductance formula of gas sensing thin film with adsorbed oxygen negative ion are given. The mesoscopic theory of nano-thin film conductance activity energy was proposed, and using the corrected Fermi statistic formula for the concentration of adsorbed negative ion, the theoretical curve of Eact varies with grain size r0 yield; from which, the related problems are discussed.

Experiment and Theory for the Thickness Effect of Nano Metal Oxide Gas Sensing Thin Film Optimum Size of Crystal Grains and Theory of Mesoscopic Effect

For pt. I see ibid., p.Z001463-8, (2006). The existence of the optimum film thickness and optimum grain size of nano metal oxide gas sensing thin films is given by experiment results. The existence of the optimum grain size is examined theoretically to be a new mesoscopic effect, resulting from the failure of Fermi statistic law of the adsorbed negative oxygen ion concentration when the grain size reduces to a certain range. According to Kubos theory that as the grain size reduces to a characteristic length rm the grain would be neutrality, Fermi statistics is modified, and therefore, the theoretical result of the optimum grain size r0*=2rm is yielded. With the Kubos formula of electron work function, the values of rm and r0* can be estimated, which consist with the experimental results