高度取向铌酸铋钙薄膜的制备及其构效关系的研究

发布时间：2018-06-03 21:03

本文选题：CaBi_2Nb_2O_9 + 磁控溅射　；参考：《山东大学》2017年硕士论文

【摘要】：在器件向微型化和集成化方向发展的要求下,铁电薄膜因具有良好的铁电性、压电性、热释电性等物理特性,在微电子学、光电子学和微机电系统等领域具有广泛的应用前景。铋层钙钛矿结构铁电薄膜因具有高抗疲劳特性、低老化速率、高居里温度等特点在高温高频领域有很大应用潜力。然而,铋层钙钛矿结构铁电材料特殊的层状结构(a≈bc),使晶粒方向调整较为困难,薄膜倾向于沿c轴方向生长,而极化却主要存在于a-b面内,这种极化方向和生长方向的矛盾导致此类结构的陶瓷铁电极化和压电活性较低。CaBi2Nb2O9(CBNO)作为一种典型的铋层钙钛矿结构铁电体,是由(CaNb207)2-层与(Bi202)2+层在c轴方向上交替生长得到。CBNO薄膜,居里温度高达943℃,在高温铁电压电领域有非常大的发展前景。但在薄膜器件的实用化过程中,还需要解决其极化强度低,压电系数低等问题。本课题的主要研究内容是从应变工程的角度出发,结合晶格匹配理论,对薄膜的取向以及应力状态进行调控,并采用射频磁控溅射的方法制备高度取向的CBNO薄膜。研究应变状态,基体取向,薄膜厚度,底电极厚度,降温气氛,沉积温度和缓冲层对薄膜的晶体结构,微观形貌以及电学性能的影响,进而提高CBNO薄膜的介电、铁电及压电性能,最终在Si基体上实现CBNO薄膜的中低温制备。通过本研究,取得以下成果:1.CBNO薄膜的应变调控生长(1)在MgO基体上应变调控生长(200)/(020)择优取向的CBNO薄膜。CBNO薄膜晶粒在生长过程中受到界面能和弹性能的共同影响,c轴取向的晶粒(c轴晶粒)外延生长,a轴取向的晶粒(a轴晶粒)从c轴晶粒的附近生长。(2)在MgO(100)、(110)单晶基体上生长CBNO薄膜,利用面内拉伸应力,改善其介电性能。因a轴晶粒及与a轴夹角较小的其他取向晶粒含量的增多,两者的剩余极化强度提高显著(Pr～13 μC/cm2)。(3)CBNO薄膜的电滞回线均发生了收缩和倾转,较为细长。用优化的肖特基模型对薄膜漏电流密度曲线进行拟合,研究发现薄膜中存有高浓度的空间电荷。(4)增大CBNO薄膜厚度,其介电性能得到优化。外加电场为2750kV/cm时,400 nm CBNO薄膜的饱和极化强度为90 μC/cm2,对应的储能密度为86.8 J/cm3,为CBNO薄膜在储能应用方面打开了新思路。2.CBNO薄膜的取向生长(1)分别在YSZ(100)基体和以YSZ作为缓冲层的Si(100)基体上生长具有a轴择优取向的CBNO薄膜。(2)以YSZ作为缓冲层,在Si(100)基体上生长的CBNO薄膜的介电和铁电性能显著提高。由于其介电常数高,剩余极化强度大,以及Si单晶基体较大的泊松应变,使得CBNO薄膜异质结构的压电系数d33(～30 pm/V)提高明显。3.CBNO薄膜的中低温制备(1)镀膜温度分别为450℃、500℃、600℃,在Si(100)基体上制备了结晶性良好且为(115)择优取向的CBNO薄膜,镀膜温度为500℃、600℃的CBNO薄膜的铁电性能良好,而450℃C薄膜的电学性能需进一步提高。(2)调整镀膜功率为70W、100W、120W,发现提高镀膜功率,有利于提高CBNO薄膜的电学性能,尤其是介电性能。(3)引入LaNiO3(LNO)缓冲层,对中低温下CBNO薄膜的性能并没有起到有利的影响,反而降低了 CBNO薄膜的铁电和介电性能。
[Abstract]:The ferroelectric thin film has a wide application prospect in the fields of microelectronics, optoelectronics and microelectromechanical systems due to the good ferroelectric, piezoelectricity and pyroelectric properties. The ferroelectric thin film of the bismuth layer perovskite structure has high fatigue resistance, low aging rate and high rate. Curie temperature and other characteristics have great potential in the field of high temperature and high frequency. However, the special layered structure (a BC) of the bismuth perovskite structure ferroelectric material (BC) makes the grain direction more difficult to adjust, and the film tends to grow along the direction of the c axis, but the polarization is mainly in the A-B surface, and the contradiction between the polarization direction and the direction of growth leads to such junction The ferroelectric polarization and the piezoelectric activity of the ceramics are lower.CaBi2Nb2O9 (CBNO) as a typical bismuth layer perovskite ferroelectrics. It is a.CBNO film formed by the alternating growth of (CaNb207) 2- layer and (Bi202) 2+ layer in the direction of C axis. The Curie temperature is up to 943 degrees C, and it has a great development prospect in the field of high temperature ferroelectric piezoelectricity. In the process of utilization, it is necessary to solve the problems of low polarization strength and low piezoelectric coefficient. The main research content of this topic is to adjust the orientation and stress state of the film by using the lattice matching theory from the angle of strain engineering, and to prepare the highly oriented CBNO film by RF magnetron sputtering, and study the strain state. The influence of substrate orientation, film thickness, bottom electrode thickness, cooling atmosphere, deposition temperature and buffer layer on the crystal structure, micromorphology and electrical properties of the thin film, and then improve the dielectric, ferroelectric and piezoelectric properties of CBNO films, and finally achieve medium and low temperature preparation of CBNO films on the Si matrix. The following results are obtained: 1.CBNO thin The strain regulation growth of the membrane (1) the strain regulated growth (200) / (020) preferred orientation of the CBNO film.CBNO film on the MgO matrix is influenced by the interfacial energy and the elastic properties. The c axis oriented grain (c axis grain) grows, and the a axis grain (a axis grain) grows from the c axis grain. (2) in MgO (100), (110) The CBNO film is grown on the single crystal matrix, and the dielectric properties are improved by using the tensile stress in the surface. The residual polarization strength of the a axis grain and the smaller angle of the a axis is increased significantly (Pr to 13 mu C/cm2). (3) the hysteresis loops of the CBNO film are both shrinking and tilting, and the optimized Schottky is used. The model is used to fit the leakage current density curve of the film. It is found that there is a high concentration of space charge in the film. (4) the dielectric properties of the CBNO film are optimized. When the applied electric field is 2750kV/cm, the saturation polarization of the 400 nm CBNO thin film is 90 Mu C/cm2 and the corresponding energy storage density is 86.8 J/cm3, which is the application of CBNO film in energy storage. The orientation growth of the new thought.2.CBNO film was opened (1) to grow CBNO films with a axis preferred orientation on the YSZ (100) matrix and the Si (100) matrix with YSZ as the buffer layer. (2) the dielectric and ferroelectric properties of the CBNO thin films grown on the Si (100) substrate increased remarkably with YSZ as the buffer layer. High intensities and larger Poisson strain of Si single crystal matrix make the piezoelectric coefficient d33 (~ 30 pm/V) of CBNO thin film heterostructures increase. The temperature of medium and low temperature of.3.CBNO film (1) is 450, 500, 600, respectively, and the CBNO film with good crystallinity and (115) preferred orientation is prepared on Si (100), and the coating temperature is 500. The ferroelectric properties of CBNO film at 600 C are good, and the electrical properties of C film need to be further improved. (2) the coating power is 70W, 100W, 120W. It is found that improving the coating power is beneficial to improve the electrical properties of the film, especially the dielectric properties. (3) the LaNiO3 (LNO) buffer layer is introduced, and the performance of the CBNO thin film at middle and low temperature is not the same. On the contrary, the ferroelectric and dielectric properties of CBNO films are reduced.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB383.2

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