Growth and Broad-Band Dielectric Behavior of Barium Titanate Thin Films.

BaTiO_3 thin film has a high dielectric constant, which is potentially very useful in integrated electronics as a replacement for SiO _2. The low temperature growth and dielectric characterization of BaTiO_3 thin film are essential. In this thesis, an ion-assisted deposition process, called the Reactive Partially Ionized Beam technique, was investigated for the preparation of high quality amorphous and polycrystalline BaTiO_3 thin films. The dielectric was experimentally characterized over a broad frequency domain using specially designed test vehicles and measurement techniques. Amorphous and fine-grained polycrystalline BaTiO _3 thin films were grown near room temperature and at 600^circC. The thermal, optical and microstructures of the films were studied with respect to the stoichiometries of the films and growth conditions. The frequency dispersion behavior of the dielectric constant and the loss tangent of the films were measured in the frequency range of 10 ^3-10^{11} Hz via specially designed and fabricated high frequency test vehicles. The behavior was compared with the theoretical models derived from the classical dispersion theory. The results provide experimental evidence to support the speculation that the dielectric constant of polycrystalline BaTiO _3 thin films has a dispersion over the RF frequency range. The dispersion for fine-grained BaTiO _3 thin films has the characteristic of the Debye relaxation with a relaxation frequency of 10^7 Hz. The dispersion identified at 2times 10^9 Hz for bulk BaTiO_3 is not observed in fine -grained film, possibly due to the diminished size of the ferroelectric domains. In comparison, the dielectric constant of amorphous BaTiO_3 thin films is proved to be non-dispersive up to optical frequencies because of the absence of any long range order.