Preparation Of Formaldehyde OTFT Gas Sensor

HCHO （formaldehyde） is a colorless and strongly stimulating smell gas at roomtemperature, is easily soluble in water, alcohol and ether, as well an important chemicalindustrial material and organic solvent, however, HCHO is very poisonous, prolongedexposure to low concentrations of formaldehyde, people feel uncomfortable, headache,pain in the eyes, respiratory allergies. So it is of great necessity to detect the HCHO.Many methods have been developed to detect HCHO, and the gas sensor gets muchattention in this field. Compared with other gas sensors, OTFT has advantages of fastresponse, and good selectivity, and can work under ambient conditions, etc.The structure of OTFT was bottom electrode structure and bottom touch, highlydoped N-type monocrystalline silicon was used as substrate with the thickness of450μm, and the thickness of insulating layer SiO2was about195nm, interdigitalelectrode size is25μm, the titanium/aurum thin films were made as the source/drainelectrodes, the thicknesses was about20nm and50nm, respectively, the OTFT with theratio of channel width to length as160were chosen to fabricate sensors in this paper.Preparing the films by air-brushing, then a series of OTFT gas sensors were made.Detected the electrical characteristics and the response for formaldehyde of the OTFTsensor by Keithley-4200，calculated mobility, relative response, response time, recoveryof performance parameters etc, observed the Surface morphology of the composite filmby SEM and AFM.The experimental program was divided into four main parts:（1） prepared theP3HT and P3HT/ZnO sensitive thin films, then explored their characteristics. Theresults showed that the composite film of P3HT/ZnO combined the conductivity ofP3HT with the sensitivity of ZnO to formaldehyde, also the composite film overcomethe high temperature working conditions and could be detected at room temperature.（2）two sets of comparative experiments were designed for P3HT/ZnO composite film,one researched the influence of different airbrushed dosage on the composite films, theother researched the influence of different ratios of P3HT/ZnO on the composite films.The results showed that1.0ml volume of the composite solvent and the1:1ratio of P3HT/ZnO made the excellent film.（3） under the best experiment condition, theexcellent film was prepared, then we studied its response to the low concentration offormaldehyde, the repeatability at the atmosphere of100ppm formaldehyde, the stabilityin the air, the selectivity by compared toluene, carbon monoxide, methane, hydrogensulfide and ammonia. The results showed that the composite films got a goodrepeatability, a poor stability with only7days, a brilliant selectivity, the lowestdetection concentration of formaldehyde was10ppm.（4） Compared the characteristicsof P3HT with other inorganic metal oxide composite film, the major point was focusedon contrast between P3HT/Fe₂O₃with P3HT/ZnO. The results showed that P3HT/ZnOOTFT behaved a more prominent electrical output characteristics and brilliantformaldehyde sensitive response, the P3HT/ZnO composite film is more suitable for thepreparation of formaldehyde OTFT gas sensor...