Fabrication And Characteristics Of Gas Sensors For Indoors Hazardous Gases

The preparation, characteristic and application in different fields of undoped and indium doped SnO₂ thin films were described in this paper. The study was focused on the improvements of the selectivity and low temperature operation of the gas sensors. Indium doped tin oxide thin films with different In/Sn ratio, and a P-N combined gas-sensor-array based on the p and n type tin oxide was fabricated by sol-gel method. The electronic properties and gas sensitivities of the above mentioned sensors were characterizedThe results showed that the carrier concentration and conducting type of the oxide films varies as the In/Sn ratio changes. So the response of each individual sensor to specific gases in the gas-sensor-array was different, which lead to the excellent selectivity of this array. Gas detection measurement of the array showed good selectivity for 4 common hazardous indoors gases (formaldehyde, benzene, methylbenzene, and dimethyl benzene). The resistance-temperature relation (R-T) of a gas sensor based on undoped SnO₂ film was also studied in this paper. It is found that in R-T curve, different gases have different slopes, which could be used to distinguish gases, thus increases the selectivity of the gas sensor. Molecule orbital energies of above mentioned four common hazardous gases calculated using WinMOPAC 2,0 indicated differences in the energy of the lowest unoccupied molecule orbital (LUMO) was responsible for the different slope in R-T curves.In addition, a thin films gas sensor based on nano-ZnO were prepared by a new method invented by our group. The response of nano-ZnO thin films to several common hazardous gases have been measured, the results showed that gas sensor based on such nano-ZnO particle films are of high sensitivity for above mentioned four common indoors hazardous gases even at room temperature.