Effect of Al concentration in grain and grain boundary region of Al-doped ZnO films: a dielectric approach

Aluminium-doped zinc oxide (ZnO : Al) films have been deposited by RF magnetron sputtering on Pyrex glass substrates. The structural, electrical and optical properties of films as a function of Al concentration have been studied. Al-doped films exhibit high optical transparency and a reduction of resistivity with increasing Al concentration. The minimum resistivity value is found to be rho = 2.2 x 10(-3) Omega cm as compared with similar to 10(4) Omega cm, for undoped ZnO. The optical band gap is observed to follow a Burstein-Moss shift with the increase in the concentration of Al doping and shows the maximum band gap of 3.53 eV. Relative variation of the grain and grain boundary scattering with doping concentration has been investigated with impedance spectroscopy.