Doping optimization and surface modification of aluminum doped zinc oxide films as transparent conductive coating

Aluminum doped zinc oxide (ZnO:Al) films were grown using spray pyrolysis technique. Effect of doping on structural, electrical, optical and morphological properties was studied. Aluminum doping improved the prominence of [002] growth while maintaining the grain size ~ 48 nm. Using an intermediate Al/Zn atomic ratio in precursor (1.5:100), we could achieve a low resistivity ρ ~ 7 × 10− 4 Ωcm. These films possessed an average visible transmittance ~ 88%, an optical gap ~ 3.7 eV and plasma wavelength at 1.87 μm. A simultaneous use of methanol and iso-propanol in the precursor lead to a moderate surface roughness ~ 12 nm. The films were surface modified using wet chemical etching in diluted hydrochloric acid, for varied time intervals (5 s–15 s) and etchant concentrations (0.125%–1%). The etching experiments could be used to know the building of the film as also to modify the surface for desired optical and morphological properties.

► High conductivity ZnO:Al films prepared by spray pyrolysis.
► Physical properties very competitive as transparent conductor.
► Co-use of methanol and iso-propanol made smoother but compact films.
► Wet chemical etching helped to modify the surface and understand the growth.