Effect of RF power on structural, morphological and optical properties of NiO thin films

Nickel oxide (NiO) thin films were deposited on Si substrate by using RF magnetron sputtering at 100 °C. The RF power was varied as 150, 200, 250 and 300 W. The effect of varying RF power on structural, morphological and optical properties of the films was investigated using X-ray diffraction (XRD), field emission electron microscopy (FESEM) and UV-vis reflectance spectroscopy, respectively. XRD analysis showed that NiO films exhibited cubic structure with preferred orientation along (200) plane for films prepared at 150, 200 and 250 W. The preferred orientation was changed from (200) to (111) when the RF power was increased from 250 to 300 W. The crystallinity of the films was improved with increasing the RF power from 150 to 200 W, however, it was deteriorated at higher sputtering power. The optical band gap of the films was increased from 3.57 to 3.6 eV as the RF power was increased from 150 to 200 W, however, it was reduced to 3.50 eV followed by an increase to 3.54 eV with further increase of the RF power to 250 and 300 W, respectively.