Preparation Of BaSn_0.15Ti_0.85O₃ Thin Films By Pulsed Laser Deposition And Research Of The Dielectric Properties

Recently, voltage-controlled tunable materials with middle permittivity and low loss at room temperature has attracted a great interest in the applications of dielectric materials for miniaturization tunable devices, such as phase shifters, filters and resonators. Ferroelectric thin films, such as the?BaxSr1-x?TiO₃?BST? thin film, have been widely investigated and used in practice for their high dielectric constant, high tenability, large tenability and small temperature coefficient of the resonator frequency. The researchers have carried out a lot of work on the piezoelectric media materials, which are represented by BST, and many meaningful results have been obtained. However, the high dielectric loss, large leakage current density limits their further practical application. Therefore, New materials are in urgent need to research for tunability application. Among other perovskite oxide, Ba(Ti_xSn_1-x)O₃?BTS? is a solid solution compound that exhibits paraelectric or ferroelectric properties depending on the specific composition and has been paid much attention due to its low loss and tenability and shows wide application prospect in the aspect of voltage-controlled tunable materials.BTS is a solid solution of two compounds which is composed of barium titanate and barium stannate. They have ABO₃ type perovskite structure and are similar in structure, so, barium titanate and barium stannate can be blended in any proportion. Similar to other barium titanate based solid solutions, the properties of BTS can be regulated by the composition and microstructure. The effect of Sn of BTS is similar to Zr of zirconium barium titanate, which causes the Curie peak of solid solution moving to low temperature. If the proportion of tin element in solid solution is appropriate, the peak value of dielectric constant will greatly increase.The properties of the ferroelectric thin films are known to be strongly dependent on the preparation parameters such as substrate temperature, oxygen pressure and film thickness. To determine the growth conditions of BTS ferroelectric thin films by PLD is thus essential for future applications. Substrate temperature is one of crucial parameters for the crystal growth of thin films that has a significant effect on the mobility and kinetic energy of adatoms on the substrate, as well as crystallization and electrical properties of the thin films. In this paper, BTS thin films were deposited on Pt-coated Si substrates by using the PLD process. To obtain large tunability and low dielectric loss, the effects of substrate temperature on film phase structure and surface topography were investigated. The dielectric properties and leakage current density of BTS thin films which was effected by substrate temperature were also systematically investigated. The effects of substrate temperature on the structure, dielectric properties and leakage current density of BTS thin films were investigated. The results indicate that the substrate temperature has a significant effect on the structural and dielectric properties of BTS thin films. The thin films exhibit polycrystalline perovskite structure in the substrate temperature range from 550 °C to 750 °C. The dielectric constant and loss tangent of the BTS thin films deposited at 650 °C are 341 and 0.009 at 1 MHz, respectively. The tunability is 72.1% at a dc bias field of 400 kV/cm, while the largest figure of merit?FOM? is 81.1. In addition, the effect of the substrate temperature on the leakage current of the BTS thin films was also discussed. The combination of low loss, medium permittivity and low leakage current density with superior voltage tunability may make the BTS thin films promising for tunable capacitor applications.