Effect of Cu interlayer on opto-electrical parameters of ZnO thin films

In this paper, we focused our attention on the tailoring of structure and optical analysis as a function of Cu interlayer between the ZnO layers. The Cu interlayer was deposited by magnetron sputtering, while the ZnO layers were deposited by atomic layer deposition. Morphological analysis, based on grazing incident X-ray diffraction patterns and scanning electron microscope images, revealed formation of crystalline phase and a successful incorporation of Cu into ZnO. The estimated average crystallite size increased from 8.64 to 12.05 nm as Cu interlayer thickness increased from 20 to 70 nm. The averaged value of the surface roughness was determined, from both the profilometer and the XRD measurements. The determinations of the optical band gap and the nature of optical transition were performed by the analysis of absorption spectrum. Also, some physical quantities, such as optical density OD and skin depth δ, were estimated. Optical absorption studies revealed that all the films have a direct allowed transition. A shift in the optical energy band gap E g from 2.75 to 2.43 eV as a function of Cu interlayer thickness was observed. The linear refractive index ( n ) was analyzed to determine the metallization criterion M, the reflection loss function R L , the transmission coefficient T and the relative density D r . Moreover, we showed that the doping of ZnO with different thickness of Cu interlayer enhances its optical activity and electrical conductivity as well, which makes it useful for photocatalytic application and sensor device fabrication in particular conditions.