Enhanced electrical properties of multilayer Ba(Zr_0.2Ti_0.8)O₃/Ba_0.6Sr_0.4TiO₃/Ba(Zr_0.2Ti_0.8)O₃thin films for tunable microwave applications

Excerpt

Ferroelectric thin films based on BaSrTiO₃ (BST) have been intensively studied for a large field of applications, such as ultra-large-scale integrated dynamic random access memories (DRAM), and field effect transistors [1, 2]. To develop a high performance microwave tunable devices, it is required a material with suitable dielectric constant, high tunablility, and low dielectric loss, to achieve high figures of merit. However, the disadvantages of ferroelectric films include high dielectric constant, relatively high dielectric loss, and the degradation of ferroelectric in hybrid structures. In order to further increase the figures of merit, much effort has been made to develop modified BST thin films. The introduction of dopants, such as Al₂O₃ and MgO, into BST has been demonstrated to be an effective way to improve the figures of merit for microwave tunable devices application. Usually it has been observed that the reduction in losses of BST thin films doped with Al₂O₃ or MgO is accompanied by the reduction in tunability [3, 4]. In addition, their reproducibility and the stability of the materials needs to be improved [5, 6]. …