Volatile Organic Compound Gas Sensing Applications of n-Type SnO2 and p-Type CuO Based on Thin Films

The present work is a comparative study of cupric oxide (CuO) and tin oxide (SnO 2 ) thin films deposited by spray pyrolysis and their sensitivity towards volatile organic compounds. The film structure and morphology were analyzed by x-ray diffraction, scanning electron microscopy and atomic force microscopy. The obtained results indicate that the synthesized films exhibit small grains size with porous and rough surfaces. This morphology enhances the surface-to-volume ratio necessary for gas sensing efficiency. The prepared CuO and SnO 2 films were tested for ethanol and methanol vapor. The organic vapor concentration was varied from 20 ppm to 500 ppm at different temperatures ranging between 20°C and 200°C. The SnO 2 -based sensor showed good sensitivity, selectivity and repeatability, as well as fast response and recovery towards ethanol gas at room temperature. However, the CuO sensor exhibited high sensitivity and selectivity towards methanol vapor at 50°C operation temperature. The detection limit was in the range of 23–28 ppm for the tested gases. The obtained results suggest the possibility of fabricating a high-performance and low-cost volatile organic sensor using n -type and p -type metal oxide sensitive layers.