Investigation of optical properties of aluminum-doped zinc oxide films via flow-limited field-injection electrostatic spraying

Zinc oxide films doped with 0 at. %-5 at. % aluminum are fabricated by flow-limited field-injection electrostatic spraying using a sol-gel processed precursor. X-ray diffraction and Rietveld analyses indicate that the films are highly (002)-oriented with large crystallites and that the lattice constants of the doped-ZnO tend to decrease with Al doping below the values of undoped-ZnO. Optical properties were measured by ellipsometry and analyzed using the Drude model of permittivity. The electron scattering rate is calculated to be minimal at 3 at. % Al, which may indicate a reduction in the ionized impurities due to the lattice strain and the absence of Al clusters, which is enabled by the sol-gel precursor. Insights are offered regarding the effects of Al doping on film density, electron concentration, and background permittivity, which may prove important in tuning the film properties for plasmonic applications.