Growth and gas sensing properties of doped tungsten oxide films

Abstract

This thesis is concerned with the thin film growth and characterization of Fe Si and C doped tungsten oxide (WO3-x) for gas sensing applications The films were grown by RF magnetron sputter deposition in pure Ar atmosphere at room temperature followed by post-deposition annealing in air at 550 ~ 750 ?C The composition and microstructure of the grown films as well as the valence state of tungsten ions were studied by XRD SEM EDS and XPS The electric resistances of the films in pure air (Ra) and in the air containing 5 ppm each of the gases of CO CO2 methanol and ethanol (Rg) were tested according to which the gas sensitivity (S) was defined as S=Ra/Rg The effects of film composition microstructure and dopant on the gas sensitivity and the response and recovery times were discussed The results showed that at the working of 350 ?C the 35 0 % C doped WO3-x films had the best sensitivity for alcohols i e S=5 89 and 5 42 for ethanol and methanol respectively compared to S=1 71 and 1 19 for CO and CO2 respectively The response/recovery times of the 35 0 % C doped WO3-x films were 7/244 s and 8/463 s for ethanol and methanol respectively

Date of Award	2020
Original language	English
Supervisor	Xiao-Ding Qi (Supervisor)