Optical and structural properties of porous zinc oxide fabricated via electrochemical etching method

• Hillock like porous structure zinc oxide was obtained via electrochemical etching.
• Anisotropic dominance etching process by KOH etchant.
• Reststrahlen features are sensitive to multilayer porous structure.
• Determination of porosity from IR reflectance spectrum.

We investigated the optical and structural properties of porous zinc oxide (ZnO) thin film fabricated by ultraviolet light-assisted electrochemical etching. This fabrication process used 10 wt% potassium hydroxide solution as an electrolyte. Hillock-like porous ZnO films were successfully fabricated according to the field emission scanning electron microscopy results. The cross-sectional study of the sample indicated that anisotropic-dominated etching process occurred. However, the atomic force microscopic results showed an increase in surface roughness of the sample after electrochemical etching. A resonance hump induced by the porous structure was observed in the infrared reflectance spectrum. Using theoretical modeling technique, ZnO porosification was verified, and the porosity of the sample was determined.