This study involves the preparation of copper oxide (CuO) thin films on glass substrates for gas-sensing applications via direct current (DC) reactive sputtering. X-ray diffraction (XRD) analysis results indicate that the CuO films possess a polycrystalline structure with a preferred orientation along the (110) direction. The surface roughness was analysed using atomic force microscope (AFM) techniques. The films exhibit roughness values (33.2, 54.85, and 21,44 nm) at the applied voltage (480, 580, and 680 V), respectively. The field-emission scanning electron microscope (FE-SEM) images show CuO nanoparticles with a uniform, homogeneous distribution. The particle sizes of the prepared target nanoparticles start to grow with increasing the applied voltage from (480 – 680 V). The average particle width (diameter) was found to be about (26.25 – 69.1 nm). The optical properties of the prepared copper oxide films in the range (300 – 1100 nm) showed that the optical energy gap decreased gradually from (2.78 – 2.36 eV) with increasing applied voltage from (480 – 680V). CuO thin-film sensors exhibited high sensitivity and responded quickly to nitrogen dioxide (NO2) and ammonia (NH3). So, it is observed that exposure of the CuO-based sensor material to a NO2 atmosphere decreases the sensor's resistance, whereas exposure to NH3 increases it.
Hamadan et al. (Wed,) studied this question.