Room temperature photoluminescence and spectroscopic ellipsometry of reactive co-sputtered Cu-doped ZnO thin films

In this present work, reactive co-sputtering (DC) has been used to deposit the pure ZnO and Cu-doped ZnO (Cu-ZnO) thin films on a glass substrate. The copper atoms are subsumed into ZnO thin film by co-sputtering(RF) of a pure copper target. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Raman spectroscopy, Photoluminescence spectroscopy (PL), UV-Visible spectroscopy, and ellipsometry were used to examine pure ZnO and Cu-doped ZnO thin films. XRD reveals the wurtzite crystal structure for both pure and Cu-doped ZnO thin films. FESEM images show the dense and uniform surface morphology of all thin films. Energy-dispersive X-ray analysis (EDS) confirms the uniform distribution of copper dopant and variation in doping percentage in the Cu-doped ZnO films. The PL spectra of Cu-doped ZnO film have strong violet emission which shows a variation in zinc vacancy (V-Zn) defect density levels. UV-Vis-NIR spectroscopy has confirmed a slight increase in optical band gap by copper doping. The refractive index, roughness, and film thickness have been calculated using spectroscopic ellipsometry and found to increase with Cu doping concentration.