Effects of Al doping concentration on optical parameters of ZnO:Al thin films by sol-gel technique

ZnO:Al thin films doped with different aluminum concentration were deposited on (0 0 0 1) sapphire substrates by sol-gel technique. Kramers-Kronig relationship was used to determine the optical parameters of ZnO:Al thin films in wavelengths with a range of 300-600 nm. Calculated results show that all optical parameters keep constant in the visible region. The refractive index, the extinction coefficient and the real and imaginary components of dielectric are ∼1.6, ∼0.08, ∼2.5, and ∼0.27, respectively. Optical constants change distinctly near the optical absorption edge. In the ultraviolet region, doping concentration strongly affects the optical parameters of ZnO:Al thin films. Optical parameters tend to decrease with increasing doping concentration