Investigation of the structural, electrical and optical properties of Zr-doped CdO thin films for optoelectronic applications

Cadmium oxide (CdO) thin films were successfully deposited on glass substrates by the sol-gel spin coating method. The effects of the annealing temperature and Zirconium (Zr) doping on the physical properties of the CdO thin films were investigated. It was found that 550 & DEG;C is the optimal annealing temperature with a good crystallinity for the CdO thin films. Then, by using this temperature, different Zr doping concentrations (0, 1, 3, 5 and 7%) were prepared at the same experimental conditions. The X-ray diffraction (XRD) patterns of all the as-prepared thin films showed a polycrystalline nature with a face centered cubic (FCC) structure and that Zr incorporated the sites of Cadmium (Cd) up to 3% concentration, while the excess Zr doping (x > 3%) aggregated at the grain boundaries of the CdO lattice. Scanning electron microscopy (SEM) analysis revealed homogeneous and dense grains distribution with a film thickness of 30 & mu;m. The optical study showed an increase in optical transmittance of CdO with Zr doping up to 3% and then a decrease onwards within the same wavelength region. The optical band gap values increased from 2.41 to 2.67 eV with increasing Zr doping which was explained by the Burstein-Moss effect. The minimum electrical resistivity (5.32 x 10(-1) & omega; .cm) was obtained for the film coated with 3% Zr using the four-probe method.

Automated summary

Cadmium oxide (CdO) thin films were successfully deposited on glass substrates by the sol-gel spin coating method. The effects of the annealing temperature and Zirconium (Zr) doping on the physical properties of the CdO thin films were investigated. It was found that 550 °C is the optimal annealing temperature with a good crystallinity for the CdO thin films. Then, by using this temperature, different Zr doping concentrations (0, 1, 3, 5 and 7%) were prepared at the same experimental conditions. The X-ray diffraction (XRD) patterns of all the as-prepared thin films showed a polycrystalline nature with a face centered cubic (FCC) structure and that Zr incorporated the sites of Cadmium (Cd) up to 3% concentration, while the excess Zr doping (x > 3%) aggregated at the grain boundaries of the CdO lattice. Scanning electron microscopy (SEM) analysis revealed homogeneous and dense grains distribution with a film thickness of 30 μm. The optical study showed an increase in optical transmittance of CdO with Zr doping up to 3% and then a decrease onwards within the same wavelength region. The optical band gap values increased from 2.41 to 2.67 eV with increasing Zr doping which was explained by the Burstein-Moss effect. The minimum electrical resistivity (5.32 x 10(-1) Ω·cm) was obtained for the film coated with 3% Zr using the four-probe method.