| This thesis introduces in detail the application of the oxide films with high permittivity, the main problem of the materials and the method to solve these problems. In the thesis, two totally different (Ba0.5Sr0.5)TiO3 (BST) thin films were fabricated under different deposition condition and their dielectric properties were investigated, respectively. The BST films deposited in the O2 atmosphere at 650℃ show normal ferroelectric phase transition, which can be fitted with the Curie-Weiss law. However, when the film was prepared in N2 atmosphere at 550℃, the temperature-dependent dielectric relaxation is in accord with the Debye model, which is characterized by a thermally excited relaxation process.BST film prepared in Pt/Ti/SiO2/Si (100) substrate by pulsed-laser deposition (PLD) at 650℃ in O2 atmosphere has well crystallization. This film showed normal ferroelectric phase transition, and had the higher dielectric constant near Curie point, and the dielectric constant is less than 650.On the other hand, with the same target, BST film prepared by PLD at 550℃ in N2 atmosphere is quite smooth with small grains, which indicated the poor crystallization of the film. However, a high dielectric constant of 2500 at 10 kHz near room temperature was observed in this film. The dielectric constant is weakly temperature dependent above 200 K. This dielectric behavior is very similar to that reported for the so-called "colossal" dielectric constant material, such as CaCu3Ti4O12. Such an anomalous dielectric response for the BST films is ascribed to the formation of the Schottky barrier between the metallic electrode and the film surface, and the existence of the mobile charges in the film as indicated by the frequency characteristics of dielectric constant changing as the applied dc bias.
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