Tuning the optical, electrical resistivity and structural properties of DC magnetron sputtered aluminum zinc oxide films by changing the oxygen flow rate

Abstract

Thin films of aluminum zinc oxide (AZO) were fabricated by DC reactive magnetron sputtering from 50 wt% Al/Zn metallic target. The structure and optical constants of AZO films were controlled by changing the oxygen (O2) flow rate. X-Ray diffraction revealed that the addition of oxygen transforms the crystalline nature of the metallic Al/Zn to completely amorphous film at 4.5 sccm. The film density, surface roughness and deposition rate were evaluated from X-ray reflectometry measurements and they were found to decrease strongly upon transformation from metallic to oxidic sputtering mode. The optical constants were extracted from the ellipsometry measurements. As O2 flow increased from 4.5 to 30 sccm, the optical band gap increased from 4.74 to 5.33 eV whereas the refractive index decreased simultaneously. Low resistivity films were obtained as O2 flow increased from 0 to 4 sccm whereas insulating films were obtained for O2 flows above 4 sccm. The results indicated that by regulating the oxygen flow diverse ZAO films with diverse chemical stoichiometries and properties can be tuned.