Highly selective dual gas (NO & NO2) sensing depended on the operating temperature of WO3 thin films sputtered at room temperature

Abstract

We have studied the effect of film thickness (120, 180, and 286 nm) on the dual gas (NO & NO₂) sensing performance of DC magnetron sputtered WO₃ thin films deposited at room temperature. WO₃ shows strong absorption from visible light to the infrared region. An unusual peak originates at 467.6 nm (film thickness 286 nm) instead of a broadband tail, usually found in WO₃, which has been linked with oxygen vacancies. A high response of ∼196 at 150 °C for 50 ppm NO and ∼50 at 250 °C for 50 ppm NO₂ is achieved for 286 nm film, which can be associated with Localized Surface Plasmon Resonance while a low response/recovery time of ∼39s/99s is obtained for 120 nm film at 200 °C for NO gas, which is its best operating temperature too (sensor response ∼100). Even under a high humidity (90 %) environment, the sensor detected 50 ppm of NO.