铁酸铋基薄膜光伏和阻变效应的研究

发布时间：2018-03-20 08:30

  本文选题：铁电体　切入点：光伏效应　出处：《南京理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：铁电体作为一种热门的研究材料具有许多特殊的性质,如铁电性、压电性、热释电性、光伏效应和阻变效应。其中地,BiFeO_3是一种经典的铁电材料,其铁电性、压电性以及电畴反转机制等已经被广泛研究。本文着重研究了 BiFeO_3薄膜的光伏效应,通过控制BiFeO_3材料的铁电极化可以实现对其光伏效应的调控,因此该材料未来有望应用于光电传感器领域。除此之外,随着信息技术的快速发展,寻找可应用于存储器件的新材料也具有十分重要的意义。因此,本文在BiFeO_3材料的基础上掺杂元素Cr形成了Bi_2FeCrO_6,一种较新颖的铁电材料,并着重研究了 Bi_2FeCrO_6薄膜的阻变效应。本文首先利用脉冲激光沉积系统制备高质量的BiFeO_3和Bi_2FeCrO_6薄膜。然后,利用X射线衍射仪、原子力显微镜、Keithley数字源表、导电原子力显微镜和扫描隧道显微镜等仪器对所制备薄膜的表面形貌、微观结构、光伏效应和阻变效应进行了研究。本文包含以下三个方面的内容:(1)高质量BiFeO_3和Bi_2FeCrO_6外延单晶薄膜的制备;(2)BiFeO_3薄膜光伏效应的研究;(3)Bi_2FeCrO_6薄膜阻变效应的研究。具体内容如下:首先,利用脉冲激光沉积系统在制备高质量的BiFeO_3和Bi_2FeCrO_6薄膜。通过调控生长参数,寻找到薄膜较优的制备工艺窗口。利用原子力显微镜和X射线衍射仪分别对薄膜的表面形貌和微观结构进行表征,发现所制备的BiFeO_3和Bi_2FeCrO_6薄膜为表面纳米级平整的单晶外延薄膜。然后,利用 Keithley 数字源表对 SrTiO_3/La_(0.7)Sr_(0.3)MnO_3/BiFeO_3/ITO(In_2O_3:SnO_2=9:l)结构的光伏效应进行测量,成功地在BiFeO_3薄膜中观察到光伏效应。并且,该光伏效应具有以下特点:第一,短路电流和开路电压的方向均随着薄膜极化方向的反转而改变;第二,短路电流的绝对值随着光照强度以及薄膜极化强度的增加而增加;第三,随着测量温度从25 ℃上升到130 ℃,短路电流从180 nA上升到480 nA。最后,利用导电原子力显微镜和扫描隧道显微镜对SrTiO_3/SrRuO_3/Bi_2FeCrO_6结构的阻变效应进行测量,且测量所使用的探针直径分别为100nm和1nm。利用导电原子力显微镜在薄膜中观察到了稳定的、具有良好重复性的双边阻变效应;利用扫描隧道显微镜在薄膜观察到了稳定的单边阻变效应。并且,Bi_2FeCrO_6薄膜中阻变效应的开关比(薄膜中高、低阻值之比)数值均在15到122之间。总之,本文对BiFeO_3以及Bi_2FeCrO_6薄膜的铁电性、光伏效应和阻变效应进行了较为详尽的研究,该研究结果不仅对BiFeO_3和Bi_2FeCrO_6材料的进一步科学研究具有重要的意义,还对其在存储器和光电器件等方面的应用具有一定的指导作用。
[Abstract]:Ferroelectrics have many special properties, such as ferroelectrics, piezoelectric properties, pyroelectric properties, photovoltaic effects and resistance effects. Piezoelectric properties and domain reversal mechanisms have been widely studied. In this paper, the photovoltaic effect of BiFeO_3 thin films is studied, and the photovoltaic effect can be controlled by controlling the ferroelectrode of BiFeO_3 materials. In addition, with the rapid development of information technology, it is of great significance to find new materials that can be used in memory devices. In this paper, Bi _ 2FeCr _ O _ 6, a novel ferroelectric material, was formed by doping Cr on the basis of BiFeO_3 material, and the resistance effect of Bi_2FeCrO_6 thin film was studied. In this paper, high quality BiFeO_3 and Bi_2FeCrO_6 thin films were prepared by pulsed laser deposition system. Using X-ray diffractometer, atomic force microscope (AFM) and Keithley digital source table, conducting atomic force microscope (AFM) and scanning tunneling microscope (SEM), the surface morphology and microstructure of the films were studied. The photovoltaic effect and the resistance effect are studied. This paper includes three aspects: (1) preparation of high quality BiFeO_3 and Bi_2FeCrO_6 epitaxial single crystal thin films; Research on photovoltaic effect of Si ~ (2 +) Bi ~ (2 +) BiFeO _ (3) thin films. The specific contents are as follows: first, High quality BiFeO_3 and Bi_2FeCrO_6 thin films were prepared by pulsed laser deposition system. The surface morphology and microstructure of the films were characterized by atomic force microscope (AFM) and X-ray diffractometer (XRD). The BiFeO_3 and Bi_2FeCrO_6 thin films are found to be nanoscale monocrystalline epitaxial thin films on the surface. Then, the Keithley digital source meter is used to measure the photovoltaic effect of the structure of SrTiO3 / La _ (0. 7) / SrTiO _ (0.3) MNO _ (3 / BiFeO _ (3) / BiFeO _ (3) / T _ 2O _ (3) / in _ s _ 2O _ 3 / S _ 2O _ (9: 1)) structure, and the photovoltaic effect is observed successfully in the BiFeO_3 film. The characteristics of the photovoltaic effect are as follows: first, the direction of the short-circuit current and the open-circuit voltage change with the reversal of the polarization direction of the film, and second, the absolute value of the short-circuit current increases with the increase of the light intensity and the polarization intensity of the film. Thirdly, with the temperature rising from 25 鈩，

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