掺铈与掺铬对于铁酸铋薄膜铁电性影响的研究

发布时间：2018-05-01 04:46

  本文选题：铁酸铋薄膜 + 溶胶-凝胶法　； 参考：《内蒙古大学》2015年硕士论文

【摘要】：铁酸铋在室温下具有多铁性,即同时含有铁电性和反铁磁性。铁酸铋的微观结构是钙钛矿型对称三方晶系结构,属于R3c点群。由于铁酸铋(BFO)的居里温度(Tc=1103k)和尼尔温度(TN=643k)较高,它在未来的铁电存储器、传感器和光全息存储器等有着广泛的应用前景,因此受国内外许多学者的追捧。本文用化学方法之一溶胶凝胶方法(sol-gel法),配置了物质量浓度为0.2mol/L的纯铁酸铋(BiFeO3)、Bi0.9Ce0.1FeO3、BiFe0.9Cr0.1O3等前驱体溶液。然后用匀胶机在白金衬底上镀了BiFeO3、 BiFe0.9Cr0.1FeO3、BiFe0.9Cr0.1O3的薄膜,最后经扫描电子显微镜(SEM)、 X射线衍射(XRD)、拉曼光谱测试(RAMAN)、光电子能谱测试(XPS)、铁电测试和漏电流等的一系列性能测试后发现；(1)掺铈对纯铁酸铋薄膜的性能影响是,通过扫描电子显微镜发现,掺铈之后薄膜的表面形貌更加致密,孔洞明显减少。XRD结果表明,铁酸铋在32°附近的104峰和110峰,在掺铈之后合并为一个峰。这是由于铁酸铋原来的对称三方晶系相结构变为四方晶系和斜方晶系相共存结构。拉曼光谱测试的结果是,A1-1、A1-2、E-2和A1-3等声子模都有了红移,并且在428.25cm-1处的峰也消失。通过XPS测试发现,掺铈之后铁酸铋的Fe2+离子减少,因而也减少了氧空位。漏电流和铁电测试发现,由于铁二价离子的减少,使得铁酸铋的漏电流降低了约两个数量级,提高了铁酸铋的铁电性,即分别将剩余极化强度和饱和极化强度由原来的6.22μC/cm2提高到25.10μC/cm2和27.07μC/cm2到49.22μC/cm2.(2)掺铬对纯铁酸铋薄膜的性能影响是,通过扫描电子显微镜发现,薄膜的表面形貌不同于纯相铁酸铋,变得颗粒状不明显,孔洞也减少,但表面起伏度增加。由XRD晶体结构测试发现,掺Cr后除了纯相铁酸铋的主峰,还有在27.9°附近出现了新的峰,这是BiCrO3的(211)晶向主峰,还有在52.9°和57.6°附近出现了两个铬酸铋的(420)和(422)晶向峰,这表明,掺Cr使BFO原来的三方晶系相结构变为BFO和BCO共融体结构。铁酸铋的A1-1(cm-1)、A1-2(cm-1)、E-1(cm-1)、 E-2(cm-1)、E-7(cm-1)振动模由原来的79.09 cm-1、40.34 cm-1、220.83 cm-1.264、87 cm-1、613.59 cm-1蓝移后变为99.62cm-1、140.51cm-1、 222.29cm-1、268.54cm-1、682.61cm-1,而振动模A1-3(cm-1)、E-4(cm-1)、 E-6(cm-1)红移后变为170.29 cm-1、342.98 cm-1、506.34 cm-1。振动模E-3、E-5掺铈后消失,有新的模E-8出现,这一现象也进一步说明了相的变化。掺铬之后铁酸铋的Fe2+离子的减少通过XPS测试发现,对纯相BFO和BiFe0.9Cr0.1O3的薄膜多铁性测试后漏电流降低了,但对于铁电性没有增强,反而降低,这是因为Cr3+离子代替Fe3+离子后,破坏了结构的对称性,使BFO薄膜原来的极化机制变弱所致。
[Abstract]:Bismuth ferrate has polyferric properties at room temperature, that is, it contains both ferroelectric and antiferromagnetic properties. The microstructure of bismuth ferrate is a perovskite-type symmetric rhombohedral system and belongs to R3c point group. Because the Curie temperature of bismuth ferrate (BFOO) is higher than that of Nier temperature (TN643k), it will be widely used in ferroelectric memory, sensor and optical holographic memory in the future, so it has been sought after by many scholars at home and abroad. In this paper, the sol-gel method, one of the chemical methods, has been used to prepare the precursor solutions of bismuth ferrate (0.2mol/L) with mass concentration of 0.2mol/L, such as Bi0.9Ce0.1FeO3, BiFe0.9Cr0.1O3 and so on. Then the thin films of BiFeO3, BiFe0.9Cr0.1FeO3and BiFe0.9Cr0.1O3 were deposited on the platinum substrate by a rubber leveling machine. Finally, the effects of cerium on the properties of pure bismuth ferrate thin films were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRDX), Raman spectroscopy (Raman spectroscopy), photoelectron spectroscopy (XPS), ferroelectric measurement and leakage current. Scanning electron microscopy (SEM) showed that the surface morphology of the films was denser after cerium doping. The results of XRD showed that the 104th and 110 peaks of bismuth ferrate near 32 掳were merged into a single peak after cerium doping. The reason is that the phase structure of bismuth ferrate is changed into tetragonal system and oblique crystal system. The Raman spectra show that the phonon modes such as A1-1OA1-2OE-2 and A1-3 have red shifts and the peaks at 428.25cm-1 also disappear. The XPS results show that the Fe2 ion of bismuth ferrate decreases after cerium doping, thus reducing the oxygen vacancy. The leakage current and ferroelectric test show that the leakage current of bismuth ferrate decreases by about two orders of magnitude due to the decrease of iron divalent ions, and the ferroelectric property of bismuth ferrate is improved. That is to say, the residual polarization strength and saturated polarization intensity were increased from 6.22 渭 C/cm2 to 25.10 渭 C/cm2 and 27.07 渭 C/cm2 to 49.22 渭 C / cm ~ (2.2) respectively. The effect of chromium doping on the properties of pure bismuth ferrate thin films was found by scanning electron microscopy. The surface morphology of the films was different from that of pure bismuth ferrate films. It became less granular and the pores decreased, but the surface undulation increased. From the XRD crystal structure test, it is found that in addition to the main peak of pure bismuth ferrate, there is a new peak near 27.9 掳, which is the main peak of the crystal direction of BiCrO3, and there are two peaks of bismuth chromate 420) and calcareous 422) near 52.9 掳and 57.6 掳. Cr-doped BFO changed the original rhombohedral phase structure into BFO and BCO eutectic structure. 閾侀吀閾嬬殑A1-1(cm-1),A1-2(cm-1),E-1(cm-1), E-2(cm-1),E-7(cm-1)鎸�鍔ㄦā鐢卞師鏉ョ殻�

本文编号：1827794