Room-Temperature Preparation of ZrO₂ Precursor Thin Film in an Aqueous Peroxozirconium-Complex Solution

We report a deposition method for room-temperature preparation of ZrO 2 thin film using an aqueous solution. ZrO(NO 3 ) 2 ·2H 2 O was dissolved in a solvent mixture composed of H 2 O 2 and ammonia. The dissolving reaction produced a colorless, transparent peroxozirconium-complex solution which was unstable; decomposition occurred even at room temperature. Amorphous, transparent, dense ZrO 2 precursor thin films of up to 500 nm thick were prepared on a cleaned P-type Si substrate. The film showed good adhesion to the substrate as peel-off was not found after either sonication or a Scotch-tape peel-off test. The as-deposited thin film was of high purity with a composition of ZrO 1.4 (OH) 1.2 . No peroxo groups were present in the as-deposited film. Annealing caused crystallization of the amorphous film into tetragonal ZrO 2 at 500 °C and phase transformation from tetragonal to monoclinic ZrO 2 at higher temperatures. Both films showed very flat surfaces consisting of nanoparticles with homogeneous size of tens of nanometers in diameter. The optical band gap of the amorphous film was 5.0−5.75 eV, whereas it was 5.65 eV for the crystalline ZrO 2 thin film.