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

BaTiO3 films of up to 3 mu m 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 BaTiO3 sol solution derived from Ti(O-iC(3)H(7))(4) and Ba(O-iC(3)H(7))(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 BaTiO3 gel films were subject to firing at a temperature ranging from 500 to 1100 degrees C. 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 maximum value at around 850 degrees C 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 degrees C to bring a state of film to amorphous one, and the intrinsic firing at 850 degrees C was executed only at the final stage to change a state of him from amorphous to crystalline one. The dielectric constant resulted in an increase to 630 (from 430). Furthermore, the value was increased to 720 at firing time exceeding 15 min, though it had remained 630 at a firing time of 10 min. (C) 1999 Elsevier Science S.A. All rights reserved.