Gas recognition by activated WO3 thin-film sensors array

We have designed and fabricated a sensors array using WO3 thin films for gas analysis purposes. The sensing surface of the rf sputtered WO3 thin films has been differently activated by evaporated Pd, Au, Bi, Sb catalysts. The sensors have been characterized by d.c. electrical measurements for different gases such as H2S, SO2, CH4, NO, NO2 in a proper concentration range from 1 to 7000 ppm in dry air, at 180 °C. Operation of the sensors under these conditions proved to be a useful way of providing a sensitive, reproducible, reversible, stable system for gas detection of ppm level. Principal component analysis (PCA) has been used in order to classify and identify different classes of target gases. Good separation among classes of sample gases has been obtained by applied PCA methods. The preliminary results show the feasibility of the electronic nose system to discriminate and recognize various tested reducing and oxidizing gases.