Structural and optical properties of transparent conducting oxide Cd1-xCrxO thin films prepared by the sol-gel dip-coating method

Abstract

Evenly Cr-doped CdO thin films have been prepared with different percentages (0, 5, 10, 15, 20, and 30%) by the sol-gel method on glass substrates. The crystal structures of the prepared films were found to be polycrystalline nature as characterized by the X-ray diffraction (XRD) pattern. Micro-structural parameters such as lattice constant (a), average particle size (Davg), lattice strain (ε), and dislocation density (δ) were evaluated. The domains formed by the aggregation of the nano-crystallites were characterized by the field emission scanning electron microscope (FE-SEM). According to the results, the increase in surface roughness is attributed to the well spread of the crystal structure of the examined films with nanoparticles over the surface without any cracks. The optical band gap Eg increases with increasing Cr ratio from 2.49 to 2.82 eV, and Urbach energy EU decreases with increasing Cr ratio. The oscillator energy (E0), the dispersion energy (Ed) the refractive index (n), the real part (ε') and imaginary part (ε'') of the dielectric constants, and the electronic polarizability (αp) were calculated. The electrical resistivity ρRT, sheet resistance Rs decreased from 10 to 1.23 Ω m−1 with increasing the ratio of Cr.