Heavily Doped Zinc Oxide Thin Films for Nitrogen Dioxide Optical Gas Sensing

摘要

In this work heavily n-doped ZnO doped with gallium, germanium, aluminum and silicon are studied for NO_2 detection, using the sensibility of localized surface plasmonic resonance in the near infrared to the change of environmental conditions. Trivalent cations (Al~(3+) and Ga~(3+)) or tetravalent cations (Si~(4+) and Ge~(4+)) are used as dopant agents with nominal concentration of 20%, following a non-aqueous heat up colloidal synthesis. No presence of other phases like metal, dopant oxides, and binary dopant-ZnO oxides is detected by XRD analysis. It is proved by spectrophotometric analysis that introduction of doping agent causes the formation of a surface plasmon resonance in the near infrared, tunable changing dopant nature. We have demonstrated that strong sensitivity of the plasmon resonance to chemical variations at the surface of the nanocrystal make this category of materials very suitable for detection of 1000 ppm NO_2 balance in air, finding the best compromise between sensitivity, signal to noise ratio and stability of the sensor in 20% germanium doped ZnO.