|標題：Microwave properties of BST and BST/BMT thin films grown on sapphire substrate by evanescent microwave probe|
|作品名稱||Microwave properties of BST and BST/BMT thin films grown on sapphire substrate by evanescent microwave probe|
|著者||Joseph, P. T.; Chen, Yi-chun; Chu, Yin-hao; Cheng, Hsiu-fung; Tai, Nyan-hwa; Lin, I-nan|
|出版者||Taylor & Francis Inc.|
|著錄名稱、卷期、頁數||Integrated Ferroelectrics: An International Journal 77(1), pp.45-50|
|摘要||Polycrystalline (Pb,La)(Zr,Ti)O3 (PLZT) films were deposited on MgO (001) single crystal substrates using chemical solution deposition method. Structural properties of PLZT films were investigated using X-ray diffractometer. The dielectric properties of PLZT films were investigated under the dc bias field of 0−40 V using interdigital capacitors (IDC) device fabricated by photolithography and etching process. The small signal dielectric properties of PLZT films were calculated by modified conformal mapping the reflection scattering coefficient data measured using an HP 8510C vector network analyzer in 1–20 GHz at room temperature. The IDC device based on polycrystalline PLZT film exhibited about Thin films of BaxSr1−xTiO3 (BST) serial materials have the advantages of adjustable tunability and are good candidates for the application in DRAM and microwave devices. However, these films usually have loss tangent higher than the order of 0.01 at microwave frequencies. To improve the crystal structures and suppress the microwave losses, an interlayer material with good microwave properties can be used. In this present work, a low loss Ba(Mg1/3Ta2/3)O3 (BMT) thin buffer layer with varying thickness and its effect on the microwave properties of Ba0.4Sr0.6TiO3 thin films is investigated. Moreover, to overcome the spatial limit in the traditional microwave measurement, a novel technique, evanescent microwave probe (EMP) method, is used to directly probe the microwave dielectric properties of the films. This technique also provides the capability to study the dielectric mechanism in micro-scale region.
Pulsed laser deposition technique was used to synthesize thin films. The films shows (111) preferably oriented growth of BST films with the introduction of BMT layer for the films grown on sapphire substrates. As the thickness of BMT increases, this behavior is more obvious. The microwave dielectric constants (ϵ) and dielectric losses (tan δ) of the films grown on sapphire substrates have been measured by EMP. The dielectric constants of BST thin films decrease monotonously with the increase of BMT thickness. In contrast, the tan δ shows a discontinuity variation when the BMT buffer layer is deposited for 10–20 minutes.
|關鍵字||(Ba0.6Sr0.4)TiO3 thin films; Ba(Mg1/3Ta2/3)O3 buffer layer; microwave dielectric properties; pulsed laser deposition|