Photoluminescence, ellipsometric, optical and morphological studies of sprayed Co-doped ZnO films

Abstract

In this study, undoped and cobalt (Co)-doped zinc oxide (ZnO) films were successfully produced by ultrasonic spray pyrolysis (USP) technique at low temperature (350[Formula: see text]C). The optical and surface properties were investigated as a function of Co content. The optical parameters (thickness, refractive index and extinction coefficient) were determined using spectroscopic ellipsometry (SE) and it was seen that the refractive index and extinction coefficient values of Co-doped ZnO films decreased slightly depending on the increasing of Co doping. For investigation, the transmittance and photoluminescence (PL) spectra of the films, UV–Vis spectrophotometer and PL spectroscopy were used at room temperature. The transmittance spectra show that transmittance values decreased and Co[Formula: see text] ions substitute Zn[Formula: see text] ions of ZnO lattice. The optical band gap values decreased from 3.26 eV to 2.85 eV with the changing of Co content. The results of PL spectra exhibit the position of the different emission peaks unchanged but the intensity of peaks increased with increasing Co doping. Also, the surface properties of the films were obtained by atomic force microscopy (AFM) and these results indicated that the surface morphology and roughness values were prominently changed with Co doping.

Optical properties and complex refractive index of Co doped ZnO waveguide thin films elaborated by spray pyrolysis

“…In the region ranging from 500 to 750 nm we can clearly observe a decrease in the average transmittance from 84 to 57 % with the increase of cobalt concentration. The observed spectra were very similar to those obtained in the literature for Co doped ZnO thin films [21][22][23][24][25]. Due to the similar ionic radii of Zn +2 (0.60 Å) and…”