Fabrication And Investigation Of (Ba,Sr) TiO₃ And Ba_6-3xNd_8+2xTi₁₈O₅₄ Thin Films For Microwave Applications

Recently, much attention has been paid to the thin films of tunable dielectric materials for their applications in microwave agile devices, such as phase shifters, tunable filters, and voltage-controlled oscillators (VCOs). In such devices, it is desirable to have a high dielectric tunability in a certain electric field range, where tunability is defined as the variation of dielectric constant with respect to the applied voltage. Among these materials, Ba1-xSrxTiO3 (BST) thin films have been extensively investigated due to their strong electric-field dependent dielectric constant. In this work, BST thin films have been deposited by using RF magnetron sputtering. The effect of deposition parameters on the component and microstructure of BST thin films have been investigated. Microstructures, dielectric properties, and tunable properties of BST films were studied systematically. Enhanced tunable properties were obtained by the preparation of BST bilayer films, BST films with the adding of lead, and BST films annealed under electrical field. In addition, Ba6-3xNd8+2xTi18O54 (BNT) ceramics is another important microwave dielectric material due to its applications in Antenna Duplexor, but the characteristics of BNT thin films have rarely been reported. In this work, BNT thin films have been deposited by pulsed laser deposition, and the dielectric properties have also been studied. These results are nice contribution to the microwave materials. Main research results are summarized as follows:1. Based on the study of deposition parameters, the optimized deposition parameters were: 9Pa for the deposition pressure, 100W for the deposition power, and 600oC...