Optical properties of GAZO thin films deposited by RF planar magnetron sputtering at various O2/Ar flow ratios

The present study investigates the effect of oxygen admittance on the surface morphology and optical constants of gallium (Ga) and aluminium (Al) co-doped zinc oxide (GAZO) thin films deposited on glass substrates by radio frequency (RF) planar magnetron sputtering. The GAZO thin films were uniformly covered with almost spherical grains of mean diameter around 50-100 nm. In the visible region, the refractive index (n) exhibited a decreasing trend with increasing oxygen admittance and the extinction coefficient (k) was almost zero, corroborating the observed increase in transmittance with oxygen/argon (O2/Ar) flow ratio. Optical constants such as the Wemple and Didomenico (WDD) single oscillator dispersion energies (Eo and Ed), static refractive index (n0), dielectric constant (ε), plasma frequency (ωp) and free carrier concentration (Nc) were determined. Desirable surface morphology and optical properties were observed on the GAZO thin films deposited at an O2/Ar flow ratio of 0.667, indicating their suitability for optoelectronic device fabrication.