The Effect of Different Concentrations of Tellurium on the Structural and Optical Properties of ZnO Nanostructured Films Deposited by Sol-Gel Method

Undoped and Te-doped ZnO nanostructured films were prepared on glass substrates by a sol-gel technique with different atomic concentrations of Te. The deposited films were characterized to investigate the structural, surface, and optical properties. The films are polycrystalline in nature and have a hexagonal structure. The crystal structure of ZnO1 – xTex films was determined, and various crystal parameters such as 2 value, FWHM, crystalline size, lattice strain, and dislocation density were calculated. The surface morphology of the films was tailored, and it was found that as the doping concentration of Te increases in ZnO, a decrease in the grain size is observed. The transmittance spectra of undoped ZnO and Te-doped ZnO films were highly transparent (~ 80 %) in the visible region. The average transparency was increased to increase the Te doping concentration. Transmittance edges were shifted to lower wavelengths when the atomic percentage of Te concentration increased. When the concentration of Te increased, an increase in the optical band gap of the deposited films was observed. Photoluminescence (PL) shows that all nanofilms have strong peaks in the ultraviolet region and small deep-level emission peaks in the visible region, depending on the Te concentration. The PL spectra of Te-doped ZnO shows a large blue shift from 396 to 381 nm in the UV emission peak position. It was also observed that as the Te doping concentration increased, the intensities of the PL bands in the visible range also increased.