Effect of oxygen partial pressure on the optical and structural properties of Al doped ZnO thin films prepared by RF magnetron sputtering method

0.5 wt% Al doped ZnO thin films (AZO) were prepared on glass substrates using RF magnetron sputtering method. Thin films were grown at substrate temperature of 250°C, RF power of 75W, working pressure of 10 mTorr, by changing the O₂/Ar pressure ratio from 0% to 16.7%. The effects of oxygen partial pressure during the deposition process on structural and optical properties of the films were investigated using XRD, SEM, AFM, EPMA and UV-visible spectroscopy. All the AZO thin films were grown as hexagonal wurtzite phase with the c-axis preferred out-of-plane orientation. The surface roughness and grain size of AZO films decreased with increasing oxygen ratio from 10.6 nm to 3.2 nm and 94.9 nm to 30.9 nm, respectively. On the other hand, the transmittance and band gap energy of the AZO films increased from 84.7% to 92.6% and 3.24 eV to 3.28 eV, respectively with increasing the O₂/Ar pressure ratio.