Chromium oxide thin films by Ultrasonic Nebulized Spray Pyrolysis of Aqueous Combustion Mixture for gas sensing application

Fabrication of Cr2O3 thin films based chemiresistive type gas sensors by a novel and inexpensive method called Ultrasonic Nebulized Spray Pyrolysis of Aqueous Combustion Mixture is reported. The deposition of pure and adherent Cr2O3 thin films with tunable thickness is achieved by utilizing exothermic combustion reaction. The combustion mixture is made by adding stoichiometric amount of urea to the aqeous solution of chromium nitrate. The highly exothermic nature of combustion reaction leads to significant enhancement in crystallinity and porosity of the films as confirmed by x-ray diffraction and scanning electron microscopy, which makes them potential candidates for application in chemiresistive gas sensing. Further the gas sensing properties of chromium oxide films produced using combustion mixture is studied in presence of ethanol as a test gas. The response of the sensor was monitored in temperature range 200 – 375 °C. It is found that the operating temperature of chromium oxide films is considerably lowered (∼ 80 °C), when exposed to reducing gas like ethanol, compared to non-combustion films.