ZrO₂ thin films with controllable morphology and thickness by spin-coated sol-gel method

A spin-coated sol-gel method for the fabrication of highly porous or smooth ultra-thin ZrO₂ films was developed. By spin-coating sol solutions, which contained ZrCl₄ in anhydrous isopropanol, on substrates, the morphology and thickness of thin films were easily controlled by changing the concentrations of ZrCl₄ in sol solutions. A highly porous film with large specific surface area (180 m²/g) was obtained at 150 g ZrCl₄/l without the addition of templates. When the concentration of ZrCl₄ decreased to 17 g/l, the porous surface turned into a smooth thin film. A linear relationship between film thicknesses and concentrations of ZrCl₄ ranging from 17 to 3 g ZrCl₄/l was observed, and an ultra-thin film with the thickness of 1.8 nm was achieved when 3 g ZrCl ₄/l was used. Results obtained in this study clearly show that spin coating of anhydrous sol solution is an efficient method for the fabrication of ZrO₂ films with controllable morphology and thickness.