Electronic sensitization of the response to C₂H₅OH of p-type NiO nanofibers by Fe doping

Pure and 0.18-13.2 at.% Fe-doped NiO nanofibers were prepared by electrospinning and their gas sensing characteristics and microstructural evolution were investigated. The responses ((R_g - R _a)/R_a, where R_g is the resistance in gas and R_a is the resistance in air) to 5 ppm C₂H₅OH, toluene, benzene, p-xylene, HCHO, CO, H₂, and NH₃ at 350-500°C were significantly enhanced by Fe doping of the NiO nanofibers, while the responses of pure NiO nanofibers to all the analyte gases were very low ((R_g - R_a)/R_a = 0.07-0.78). In particular, the response to 100 ppm C₂H₅OH was enhanced up to 217.86 times by doping of NiO nanofibers with 3.04 at.% Fe. The variation in the gas response was closely dependent upon changes in the base resistance of the sensors in air. The enhanced gas response of Fe-doped NiO nanofibers was explained in relation to electronic sensitization, that is, the increase in the chemoresistive variation due to the decrease in the hole concentration induced by Fe doping.