Fabrication of barium titanate thin films with a high dielectric constant by a sol-gel technique

摘要

BaTiO{sub}3 films of up to 3μm thickness were prepared on a Si(100) single crystal or Pt-film deposited Si(100) single crystal substrate by a dip-coating method using a BaTiO{sub}3 sol solution derived from Ti(O-iC{sub}3H{sub}7){sub}4 andBa(O-iC{sub}3H{sub}7){sub}2. The film thickness increases with the withdrawal speed raised to the power 0.6 and is proportional to the number of application (i.e. repetition of dip-coating process). The BaTiO{sub}3 gel films were subject to firing at atemperature ranging from 500 to 1100℃. The value of dielectric constant of the film prepared on the Si(100) single crystal with deposited Pt-film, greatly depends on the firing temperature or the crystallinity. The dielectric constant attained a maximumvalue at around 850℃ of firing temperature. To increase the dielectric constant more, the firing process was modified. In a typical trial, the preliminary firing at each of ten applications was executed at 500℃ to bring a state of film to amorphous one, and the intrinsic firing at 850℃ was executed only at the final stage to change a state of film from amorphous to crystalline one. The dielectric constant resulted in an increase to 630 (from 430). Furthermore, the value was increased to 720 at firingtime exceeding 15 mm, though it had remained 630 at a firing time of 10 mm.