An investigation on linear optical properties of dilute Cr doped ZnO thin films synthesized via sol–gel process

Cr doped ZnO thin films were prepared via sol–gel method. The effects of dopant concentration (0%, 1.5% and 3%) annealing temperature and film thickness on UV–Vis spectra of prepared films were investigated. Also, the thickness and surface topology of thin films were investigated by thickness profile meter (DEKTAK) and Atomic Force Microscopy (AFM), respectively. In addition, the band gap and Urbach energy of prepared films were calculated completely for the samples. The results showed that by increasing the dopant concentrations, the microstrain of the prepared thin film structures also increases while the band-gap values decrease. Meanwhile, an increase in annealing temperature makes a decrease in band gap and microstrain of thin films. The increase in thickness resulted in red shift in band gap and reduction in interior microstrains.

► In current work, ZnO:Cr thin films were synthesized via a simple sol–gel method.
► By increasing in dopant concentration the average roughness of the film increases slightly while the thickness of these films remains constant.
► By increase in dopant concentration band gap values of thin films show a decrease while the interior microstrain shows an increase based on increase in its Urbach energies.
► By increase in annealing temperature band gap values and interior microstrains of thin films show a decrease.
► By increase in number of applied dip coating, film thickness increase from 74 nm (after 1 procedure dip coating) to 147 nm (3 procedures dip coating), band gap values and interior microstrains of thin films show a decrease.