Influence Of Electrodes And Structural Transition Layers On The Dielectric And Pyroelectric Properties Of Ferroelectric Thin Films

As two important basic properties of ferroelectric thin film, dielectricity and pyroelectricity have great applicable value on storage capacitor, waveguide, information storage unit and pyroelectric detector. Recent these years, development on ferroelectric thin film and artificial component composite ferroelectric thin film have arised new research upsurge. At the same time, some complex problems appeared to be solved, such as, electrode materials, surface effect and interface of the heterogengeity structure, which have great influence on film properties. These factors can depress the film properties or can be used. How to better control and use these factors has related to many practical problems, but there is little research about these problems. Under such background, research on the influence of electrode and structural transition layers on the dielectric and pyroelectric properties of ferroelectric thin film has been carried out, which can offer some theoretical reference for application.The GLD theory, soft mode theory and first principle calculation are three methods often used to investigate the ferroelectric phase transition at international research. Transverse Ising model is the main method to deal with ferroelectrics of order-disorder type. The developed GLD theory is used to investigate the films coated with metal or semiconducting electrodes and properties of component composite ferroelectric thin film. Transverse Ising model is used to investigate the surface effect of films with surface transition layers. The corresponding results calculated from the two methods can draw the same conclusions qualitatively, which can prove the rationality and reliability of our model and method used.Influence of electrode and structural transition layers on the dielectric and pyroelectric properties of ferroelectric thin films is investigated. The results show that the semiconducting electrodes cannot screen the surface depolarization effect, which can decrese the polarization and phase transition temperature, but improve the dielectric susceptibility and pyroelectric coefficient. Structural transition layers in film surface and structural transition layers leading by interface effect are Proterozoic, which can make the film phase transition temperature higher or lower than the bulk value, and improve the dielectric and pyroelectric properties. Imperfect conducting electrodes and structural transition layers have some similar influence on film properties. In the research from TIM theory, the tranditional single step model is developed to a multi-step model, which reflects a more realistic situation of film structure, and it is an important innovation in this dissertation.Influence of electrodes and structural transition layers on dielectric and pyroelectric properties of ferroelectric thin films have been deeply investigated from both macrocopic and microscopic level. Many theoretical results in our dissertation have accordance with experimental data and can give a reasonable description of the experiment facts reported in the literature. Our work has laid the theoretical foundation for the preparing of capacitor and pyroelectric materials with good properties, which has great significance on both theory and practice.