Effect of copper doping on the change in the optical absorption behaviour in NiO thin films

Copper doped NiO thin films have been prepared using chemical spray pyrolysis technique. Investigation of these films has been done using X-ray diffraction, Atomic force microscopy, two-probe resistivity measurements and UV–visible spectroscopy. Interesting results have been obtained from the study of optical spectra. A peak corresponding to 439 nm has been observed in the absorption spectra for 1%, 5% and 10% copper doped samples. The area of the peak increases with the increase in copper concentration. This result is consistent with the AFM data. The resistivity results show that the activation energy decreases with the increase in the copper concentration. The low temperature conduction has been explained by variable range-hopping mechanism, which fits very well for the whole temperature range and again is consistent with the absorbance data. Value addition to this study is the observation of higher absorption in the visible region, thereby a tendency towards tunability for applications.