Electrochemically Induced Sol-Gel Deposition of Zirconia Thin Films

A novel electrochemical method for deposition of ZrO₂ thin films is described. The films, 50-600 nm thick, were obtained by applying moderate positive or negative potentials (+ 2.5 V to -1.5 V versus SHE) on conducting surfaces immersed in a 2-propanol solution of zirconium tetra-n-propoxide [Zr(OPr)₄] in the presence of minute quantities of water (water/monomer molar ratios in the range of 10^-5 to 10 ^-1), which was the limiting reagent. Oxidative electrochemical formation of solvated H⁺ and reductive formation of OH^- catalyze the hydrolysis and condensation of the metal alkoxide precursor. The magnitude of the applied potential and its duration provide a convenient way of controlling the film thickness. The films consist of an amorphous phase, as revealed by XRD measurements. The effects of different parameters, such as the applied potential and its duration, the amount of added water and the current-time characteristics, were studied. A mechanism for the electrodeposition of the zirconia films which is in accordance with our findings is proposed.