Synthesis of Crystalline Barium Titanate Thin Films by Gel-Aging Process on Substrate at Room Temperature

摘要

Crystalline, crack-free barium titanate (BaTiO_3) thin films with a thickness around 500 nm were synthesized in a single-step process by spin-coating a high-concentration Ba/Ti alkoxide precursor solution (1.0mol/L) on fused quartz substrates in a saturated vapor of water/2-methoxyethanol (CH_3OC_2H_4OH) mixed solution with a given molar ratio, successively followed by aging in the same atmosphere at 50 deg C. The obtained films had a pseudo-cubic perovskite phase and smooth surfaces. Crystallization of the films took place when aged in the vapor atmosphere of the mixed solutions, but did not when aged in either of water vapor or CH_3OC_2H_4OH vapor. Moreover, the crystallization of the films has been found to strongly depend on the kind of substrates used; that is, no or only a weak crystallization occurred on metal substrates. such as Pt or Au. This may suggest that a key factor in enhancing the crystallization of a film exists at the interface between the substrate and the film.