Surface morphology dependent tungsten oxide thin films as toxic gas sensor

Tungsten oxide (WO3) films are of great importance in gas sensing technology due to its selectivity towards toxic gases. In this paper, structural, morphological and compositional properties of spray deposited and chemical vapor deposited WO3 thin films were investigated using XRD, TEM, SEM, EDAX and Raman spectroscopy. These films have monoclinic crystal structure; and a filamentous network surface for spray deposited films whereas small flake-shaped microstructure was observed on the surface of chemical vapor deposited films. These films were studied for their gas sensing ability towards toxic gases like ammonia (NH3) and sulphur dioxide (SO2) as a function of temperature and concentration. Response-recovery characteristics were studied by varying gas concentration. The spray deposited films displayed higher gas response than the chemical vapor deposited films whereas the later exhibited lower optimum operating temperature as well as faster response and recovery. A correlation between the morphological, compositional, electrical and gas sensing properties of these films is also established.