| Relaxor ferroelectrics are expected to be applied practically in the fields of integrated ferroelectrics,microelectronics,and Micro Electro Mechanical Systems?MEMS?due to its excellent properties,such as ferroelectricity,piezoelectricity,dielectricity,pyroelectric properties,etc.,and become a popular material.Meanwhile,thin films have great advantages of faster response,higher sensibility,and integrated better with silicon than the corresponding bulks.In order to promote the potential applications of relax ferroelectric thin films,it is necessary to further optimize film structure and enhance its performance.In this thesis,the relaxor ferroelectric films were fabricated and investigated using pulsed laser deposition?PLD?technique based on the preliminary work of the group.The main research contents include the following points:1.?100?-oriented epitaxial relaxor ferroelectric 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3?PMN-0.3PT?thin film was prepared using pulsed laser deposition.Effects of the deposition temperature and sputtering oxygen on the structure and electrical properties of the films were studied.?100?-oriented PMN-0.3PT epitaxial relaxor ferroelectric thin film with pure perovskite structure were fabricated on SrTiO3 single crystal substrate and SrRuO3bottom electrode by PLD technique.The phase and domain structure,ferroelectric and piezoelectric properties,and leakage current behavior were studied.Results indicated well saturated polarization-versus-electric field hysteresis loops with large remnant polarization of 30?C/cm2 and coercive field of 11 kV/mm was obtained.What's more,the analysis on the leakage current behavior proposed that linear ohmic conduction and Fowler–Nordheim tunneling were the dominant mechanism for the electric field amplitude below and above 15 kV/mm,respectively.Furthermore,the epitaxial PMN-0.3PT thin film exhibited excellent local piezoelectric response and in situ electric-field-induced domain switching behavior.These results suggest the potential applications of the present epitaxial PMN-0.3PT film in integrated ferroelectric devices.2.Combining the study of PMN-0.3PT film,in view of toxicity of lead-based materials,this paper further studied the lead-free ferroelectric films with potential applications.Mndoped0.935Bi0.5Na0.5TiO3-0.065BaTiO3?Mn-BNBT?ferroelectric thin films were prepared on silicon substrates by pulsed laser deposition.Influence of the preparation parameters on the structure and electrical properties of the films were investigated.Ferroelectric Mn-doped 0.935Bi0.5Na0.5TiO3–0.065BaTiO3?Mn-BNBT?thin film was fabricated on Pt?111?/Ti/SiO2/Si substrates by pulsed laser deposition under different deposition temperature and oxygen pressure.?100?-preferred orientation and dense films with perovskite structure have been grown.The Mn-BNBT thin film deposited at the optimized oxygen pressure of 25 Pa exhibited well-defined ferroelectric P-E loop with the average remnant polarization Pr of 27?C/cm2 and coercive field Ec of 5.7 kV/mm along with high relative dielectric constant of 1295.The leakage current characteristics were discussed and it was found that ohmic conduction behaviors and Fowler-Nordheim tunneling are main mechanisms in Mn-BNBT thin film.Moreover,the Mn-BNBT film possess favorable local piezoelectric response and multidomain states by piezoelectric force microscopy.3.La0.6Sr0.4CoO3?LSCO?buffer layer was introduced using PLD technology to further study the structure and electrical performance of the Mn-BNBT film under different preparation parameters.The LSCO buffer layer was prepared on Pt?111?/Ti/SiO2/Si substrate by PLD technology.The phase structure,morphology and roughness of LSCO film were studied under different deposition temperature,oxygen pressure.The Resistivity and roughness were 12.08???cm and 3.9 nm at optimized condition,respectively.Mn-BNBT films under different oxygen pressure were fabricated on LSCO buffer layer and their electrical properties were characterized.Compared to the films grown directly on Pt,the hysteresis loop of the Mn-BNBT thin film deposited at the oxygen pressure of 20Pa improved significantly with Pr of 34?C/cm2 and Ec of 5.2 kV/mm along with improved relative dielectric constant of 864 at room temperature of 1 kHz.By contrast,the average remnant polarization of the Mn-BNBT film at 25 Pa was about 17?C/cm2,and the coercive field was 4.7 kV/mm,the relative dielectric constant was 1017 at room temperature of 1 kHz. |
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