Preparation Of Eu_0.5Ba_0.5TiO_3-δ Film And Oxygenvacancy-related Physical Properties

Perovskite ferroeletric materials have very broad applications in the field of memory devices, because of their excellent performance. In recent years, there are more and more studies on multifunctional perovskite oxide thin films. We choose EuTiO3 to form Eu_0.5Ba_0.5TiO₃ by doping Ba elements, because EuTiO3 and BaTiO3 materials have excellent properties. We have already known that a coupling effect is existed in Eu_0.5Ba_0.5TiO₃ materias and oxygen vacancies（VO） can turn this material from antiferromagnetic phase to ferromagnetic phase. However, the research about electrical properties and other aspects are still insufficient.Based on above shortcomings. The influence of growth and annealing condition on Eu_0.5Ba_0.5TiO₃ thin films are studied in this work. At the same time, we did a series of investigations about dielectric properties of Eu_0.5Ba_0.5TiO₃ thin films. In addition, some exploratory work has done on the leakage mechanism. In this paper, the research contents and results are as follows:First of all, the perovskite Eu_0.5Ba_0.5TiO₃ ceramic target is prepared by solid state reaction. Then, Eu_0.5Ba_0.5TiO₃ films are grown on SrTiO3（001） substrates by pulsed laser deposition, the quality and stoichiometry of the films are predicted by various of measurements. The stress in the films is released and lattice constants are reduced after annealing in reducing atmosphere. According to atomic force microscope measurement results, we can draw the conclusion that the films are rougher after higher temperature annealing.Secondly, Eu_0.5Ba_0.5TiO₃ films exhibit obvious dielectric relaxation in terms of calculation and comparison, their activated energy would increase as the increasing of VO concentration. The Ti ions would migrate due to the oxygen vacancies, And the migration length would be increased as the increasing of VO content, besides,VO would induce the higher concentration of carriers. In this case, the electrons prefer pinning in ferroelectric domain walls, resulting in the dipole couple between electronic and Ti ions. The dielectric relaxations in films were further studied.In addition, we conclude the leakage mechanism of Eu0.5Ba0.5Ti O3 films through measurements and calculations. It is conformed that the ohm conductive mechanism is in the high temperature. According to the X-ray photoelectron spectroscopy results of different samples annealing in 2h and 10 h, the concentration of oxygen vacancies decreased as the reducing of annealing time. As a kind of impurity doping, VO can affect the conductivity of films, thus the leakage current density is also affected.In conclusion, high quality of Eu_0.5Ba_0.5TiO₃ films were grown by PLD and oxygen vacancies were introduced during annealing process. We tuned the dielectric relaxation successfully by controlling the concentration of VO. And it is proves that the oxygen vacancies can effectively control the leakage current density. And further investigations are still needed.