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.