Dielectric Properties of (Ba, Sr)TiO3 Thin Films and their Correlation with Oxygen Vacancy Density

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Abstract
This paper describes the dielectric properties of (Ba, Sr)TiO3 (BST) thin films deposited by rf magnetron sputtering, focusing on their correlation with the oxygen vacancy density in the films. The dielectric properties specific to the BST films can be explained by considering the influence of the dielectric relaxation phenomenon following a power law dependence on time in the time-domain measurement and on frequency in the frequency-domain measurement. From an electrical comparison of the films with and without post-annealing in oxygen ambient, it is derived that charging/discharging electrons at oxygen vacancies in the interfacial Schottky depletion layer, whose width is modulated by the applied voltage, are responsible for the observed dielectric properties. Preliminary results of the oxygen vacancy density measurement using a gas-solid oxygen isotopic exchange reaction showed that the higher the post-annealing temperature, the lower the oxygen vacancy density.