| Ferroelectric thin film has been widely applied in memory, uncooled infraredpyroelectric detectors, piezoelectric MEMS and other devices. And the need of theferroelectric thin film device will increase year by year. However, there are somemainly technical barriers to restrict its rapid development in the field of IC andMEMS, such as low-temperature, low-cost, and mass production techniques for thehigh-performance ferroelectric thin films. Among many technologies of the filmfabrication, physical vapor deposition (PVD) is still dominant, but the chemicalsolution deposition (such as Sol-Gel) technology will get a place in preparationtechnologies because of its better material deposition effects and performance.Compared to other lead-free ferroelectric material, BiFeO3has the excellentpiezoelectric and ferroelectric properties, the lower the production costs, and thehigher Curie temperature, and has an attractive prospect in the field of IC and MEMSdevices. But the leakage and aging of BiFeO3film are key issues to address in theprocess of actually using. The leakage and aging are all related to the defects in thefilm. A lot of research work has shown that the doping or enhancing the degree ofcrystallization of BiFeO3film is an effective method to improve the properties of theferroelectric film. The literature about fabricating256M ferroelectric memory usingBiFe0.95Mn0.05O3has been reported. In order to improve its ferroelectric properties, wecarried out the modification research for the ferroelectric film BiFe0.95Mn0.05O3.According to defect chemistry, the high ion doping will reduce the oxygenvacancy concentration. We studied the effect the Zr4+doping on the aging behavior ofBiFe0.95Mn0.05O3ferroelectric thin films. Zr4+was doped in BiFe0.95Mn0.05O3filmswith different concentrations. And the hysteresis loop the loop before and afterapplying a high electric field was systematically studied. The film ofBiFe0.93Mn0.05Zr0.02O3shows the largest saturation hysteresis loops, the largestremaining polarization, the strongest antiaging effects, and the strongest charge retention capability, and these can illustrate that the Fe sites of conduct expensive Zr4+doping is a proven method to improve the aging properties of ferroelectric materials.The specific conclusions are as follows:(1) The P-E hysteresis loops of thin films before and after applying with the loopelectric field around700KV/cm was compared. By doping Zr4+, the double hysteresisloop was changed into a single hysteresis loop, and the saturation polarization wasalso improved through the effect of the high loop electric field;(2) P-E ferroelectric hysteresis loop of the BiFe0.95Mn0.05Zr0.02O3film has goodrectangular, the largest remaining polarization ratio, minimum ΔEc, and maximumcharge retention ability. These indicate that the Zr4+doping with2%concentration caneffectively serve to remove the aging effect. But the Zr-doping has a relatively limitedability to inhibit the oxygen vacancies and defects;(3) Size of the backswitching driving force in the BiFe1-0.95-xMn0.05ZrxO3ferroelectric film was reflected by the gap of the hysteresis loop. Zr doping isrelatively limited for the suppression of oxygen vacancies and defects.(4) After applying a high alternating electric field, the improvement of asymmetrydegree of the coercive field is mainly coming from the redistribution of the the releaseof oxygen vacancies in asymmetric electric field after disconnecting of defects inBiFe1-0.95-xMn0.05ZrxO3film, and its complex with divalent iron ions.(5) After applying a high alternating electric field, the asymmetric extent of thecoercive field was increased first and then decreased with the testing electric field.The degree of aging of the film can also be reflected by the testing electric field whenthe inflection point appearing.Bi atoms can volatilize during the annealing process, and excess bismuth is acommon method to enhance the crystallization degree of BiFeO3film. But the impactof excess bismuth oxide BiFeO3film and Pt electrode interface has not been reported.Thus the effect of Bi2O3buffer layer on film structure and electrical properties ofBiFe0.95Mn0.05O3film deposited on the substrate Pt/Ti/SiO2/Si was studied. Thespecific conclusions are as follows:(1) The Bi2O3buffer layer can cause grain growth, and reducing the oxygen ion vacancy concentration and Bi space in the film. The generation of the defected ionwas also decreased. The polarization performance and the fatigue resistance of theferroelectric were improved.(2) The Bi2O3buffer layer can be used to improve the residual polarization, reducethe coercive field, improve P-E hysteresis loop symmetry and the ability to save thecharge, reduce the ferroelectric fatigue.The reported literatures and our experimental results all show that the fight againstwear ability of the BiFe0.95Mn0.05O3film was increased. The physical mechanism ofMn-doping for improving fight against wear ability of the BiFeO3films was clarified.This also has a certain significance for improving the overall results of a similarnature and relevant to explain the film. Mn doping in the BiFeO3thin film, impact ofthe growth mode, structure and performance to raise the fight against wear ability ofthe ability of the BiFeO3film were discussed, specific conclusions are as follows:(1) When the content of Mn-doping changing from5%to20%, the growth patternsof BiFe1-xMnxO3film was changed from the (110)-oriented preferential growthdetermined from the anisotropic growth rate into (100)-oriented growth driven byminimized surface energy.(2) Mn-doping can improve the crystallization energy of the BiFe1-xMnxO3film at acertain extent, but reduces the surface energy at (100) plane.(3) The achievement of polarization BiFe0.95Mn0.05O3and BiFe0.90Mn0.10O3polycrystalline films means that the degree polarization of the film can be alsoincrease without self-epitaxial stress.(4) The aging degree of BiFe0.90Mn0.10O3film is softer than that of theBiFe0.95Mn0.05O3film, and has a more application value. |
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