| Ferroelectric (Ba,Sr)TiO3 thin films have excellent ferroelectric/dielectric properties, and own good application prospect in tunable microwave devices, dynamic random access devices, and pyroelectric detector devices. In this thesis, their research backgrounds, basic structures, preparation methods, and various characterizations of thin film properties are summarized. Then the several important problems of the current researches of (Ba,Sr)TiO3 thin films are also discussed in great detail based on the acquired research results. Secondly, We in situ monitored the epitaxial growth of SrTiO3:Nb, Ba0.5Sro.5TiO3, and YBa2Cu3O7 single layers, as well as Ba0.5Sr0.5TrO3/SrTiO3:Nb heterostructure on (001) SrTiO3 substrates with our RHEED system. The Structurally perfect and high-quality Ba0.5Sr0.5TiO3 single-crystalline thin films were prepared on LaAlO3 and MgO substrates by pulsed laser depositioa The Ba0.1Sr0.9TiO3/YBa2Cu3O7-δ heterostructure films were fabricated by pulsed laser deposition on a vicinal LaAlO3 substrates. Furthermore, The BST/Pt/Ti/SiO2/Si multilayered ferroelectric heterostructure were successfully prepared. The crystal structure, image of surface, chemical composition, and interface of heterostructure have been studied by means of modem analysis techniques XRD, EDAX, AFM, TEM, etc.The electrical properties of (Ba,Sr)TiO3 thin films andheterostructure films were measured. The main conclusions with innovationsignificance are as follows:1. We have successfully developed a high-pressure RHEED accessory with a three-stage differential pumping system for the PLD equipment in our laboratory. It can be used for in situ monitoring during the deposition of complex oxides at standard PLD conditions. We monitored the deposition of SrTiO3:Nb, Ba0.5Sr0.5TiO3, and YBa2Cu3O7single layers, as well as Ba0.5Sr0.5TiO3/SrTiO3:Nb heterostructure on (001) substrates. Pattern analyses suggest that all the films are epitaxial with good crystallinity; however the growth mode and film morphology are greatly affected by the ambient during film deposition.2. The Ba0.5Sr0.5TiO3 single-crystalline thin films were prepared on LaAlO3 and MgO substrates by pulsed laser deposition. High quality of thin films was testified by the XRD and AFM analyses. The dielectric properties of Ba0.5Sr0.5TiO3 thin films were measured at room temperature with the planar capacitor structure.3. The Ba0.5Sr0.9TiO3 YBa2Cu3O7-δ bilayer films were grown on LaAlO3 substrates with 1.2 miscut off (001) toward [010] by pulsed laser deposition The XRD and TEM analyses results prove that the BST/YBCO heterostructure films have high crystallinity and good epitaxy. The dielectric properties of BST thin film were measured at room temperature and liquid nitrogen temperature with the parallel-plate capacitor structure. The dielectric constant and loss tangent were 1200 and 0.0045 respectively at 1MHz, and 77K. A tunability of 60% and figure of merit of 133 have been achieved under ±30V DC bias, demonstrating their usefulness for frequency-agile microwave devices at the liquid nitrogen temperature.4. The highly (100) oriented Ba0.5Sr0.5TiO3 thin films with good structural property have been prepared on Si substrates with ultrathin SiO2 buffer layer, acquiring the integrated Ba0.5Sr0.5TiO3/SiO2/Si ferroelectric/semiconductor system.5. The Ba0.5Sr0.5TiO3/Pt/Ti/SiO2/Si multilayered heterostructures were successfully prepared. The dielectric properties measurement results show that thedielectric tunability is superior and the relative dielectric constant er varies at a little degree with the frequency, but Er is lower for the low-temperature deposited BST thin films, compared with the BST thin films prepared at higher temperature.6. The Ba0.7Sr0.3TiO3/Pt/Ti/SiO2/Si multilayered heterostructures were also successfully prepared. The XRD analysis shows that BST thin films are perfect perovskite structure. The EDAX analysis reveals that Ti content is rather higher in our BST thin films according to...
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