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首页> 外文学位 >Comprehensive study of composition gradient strontium doped lanthanum manganite thin films deposited by magnetron co-sputtering.
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Comprehensive study of composition gradient strontium doped lanthanum manganite thin films deposited by magnetron co-sputtering.

机译：磁控共溅射沉积组成梯度锶锶镧锰矿薄膜的综合研究。

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摘要

In this body of work, the examination of three different types of Strontium doped lanthanum manganite thin films synthesized by magnetron sputtering in the Surface and Nano Engineering Laboratory (SaNEL) allowed for the development of a detailed understanding between the processing conditions, the nano-scale structure and strain relaxation of the as-deposited thin films. Pure Lanthanum manganite and strontium doped lanthanum manganite thin films which were epitaxially grown on (001) single crystalline lanthanum alumina (LAO) and magnesium oxide (MgO) were fabricated by using single target deposition. The optimum deposition conditions were explored as preparation for synthesis epitaxial composition gradient strontium doped lanthanum manganite thin films by using co-sputtering deposition later. Surface morphology and microstructure of as-deposit thin films were characterized by atomic force microscopy (AFM), x-ray diffraction (XRD) and high resolution transmission electronic microscopy (HRTEM). Pseudo-cubic structure was identified in epitaxial lanthanum manganite thin film on LAO and strontium doped lanthanum manganite on MgO substrate, while orthorhombic structure was obtained in epitaxial strontium lanthanum manganite on LAO and lanthanum manganite on MgO substrate. Deposition rates of each target on different substrate were calculated.;ECG strontium doped lanthanum manganite thin films were prepared on the same substrates by using co-sputtering deposition with both targets deposited simultaneously. The as-deposit thin films using novel deposition procedure with different conditions were compared. The substrate temperature and power rate of each target are considered as the key factor for controlling the quality of the films. The surface morphology, microstructure and composition ratio of each element were characterized by AFM, XRD, HRTEM and XPS. A novel low angle XRD method was involved to examine the graded structure with the nano-scaled variation. It is found that polycrystalline structure with pseudo-cubic columnar domains was formed in the film on MgO substrate while epitaxial pseudo-cubic structure was obtained in the film on LAO substrate. The composition gradient of Sr doping was confirmed by EDS analysis along growth direction. The boundaries between each column were considered as a strain relaxation source in polycrystalline thin film. The ECG thin film, which is under the critical thickness, exhibits a novel strain relaxation which is considered as composition grade structure effect. Thus, the ECG buffer layer was confirmed as an effective method in strain controlling.;To further complex the structure and develop for application, a triple-layer strontium doped lanthanum manganite thin films on LAO and MgO substrates were deposited by using co-sputtering deposition with lanthanum manganite (LMO) target and strontium manganite (SMO) target. The films were designed to have a LMO layer at bottom and SMO layer on surface with both La and Sr gradient layer in between. The microstructure of as-deposit films were identified as epitaxial structure. Two epitaxial layers were found in the film on LAO substrate where orthorhombic structure was obtained below about 20 nm and pseudo-cubic structure was formed on the top. Similar strain relaxation was also observed in the film. This may produce "new" materials with the properties that are not available in the individual component phases, which might also open up various new possibilities of designing new nanoscale structures with unusual cross coupled properties.
机译：在这项工作中，在表面和纳米工程实验室（SaNEL）中对通过磁控溅射合成的三种不同类型的锶掺杂的镧锰锰薄膜进行了检查，从而使人们能够深入了解加工条件，纳米级沉积薄膜的结构和应变松弛。利用单靶沉积法制备了外延生长在（001）单晶镧氧化铝（LAO）和氧化镁（MgO）上的纯镧锰和锶掺杂镧锰矿薄膜。探索了最佳沉积条件，为以后通过共溅射沉积制备外延成分梯度锶掺杂镧锰锰薄膜的制备方法。通过原子力显微镜（AFM），X射线衍射（XRD）和高分辨率透射电子显微镜（HRTEM）表征了沉积薄膜的表面形态和微观结构。在LAO上的外延镧锰矿薄膜和MgO衬底上的锶掺杂镧锰矿中鉴定出伪立方结构，而在LAO的外延锶锶锰铁矿和MgO衬底上的镧锰矿中获得了正交晶结构。计算了每个靶在不同基板上的沉积速率。通过共溅射沉积同时沉积两个靶，在同一基板上制备了ECG锶锶镧锰薄膜。比较了在不同条件下采用新型沉积工艺的沉积薄膜。每个靶的基板温度和功率速率被认为是控制薄膜质量的关键因素。用AFM，XRD，HRTEM和XPS对每种元素的表面形貌，微观结构和组成比进行了表征。涉及一种新颖的低角度XRD方法，以检查具有纳米级变化的渐变结构。发现在MgO衬底上的膜中形成具有伪立方柱状畴的多晶结构，而在LAO衬底上的膜中获得外延伪立方结构。通过沿生长方向的EDS分析确认了Sr掺杂的组成梯度。每列之间的边界被认为是多晶薄膜中的应变松弛源。在临界厚度以下的ECG薄膜表现出新颖的应变松弛，被认为是组成级结构效应。因此，证实了ECG缓冲层是一种有效的应变控制方法。为了进一步复杂化结构并开发应用，通过共溅射沉积在LAO和MgO衬底上沉积了三层锶掺杂的镧锰矿薄膜。具有镧锰（LMO）靶和锶锰（SMO）靶。膜被设计为在底部具有LMO层，在表面具有SMO层，且La和Sr梯度层位于两者之间。沉积薄膜的微观结构被确定为外延结构。在LAO衬底上的薄膜中发现了两个外延层，其中在约20nm以下获得了正交结构，并且在顶部形成了伪立方结构。在膜中也观察到类似的应变松弛。这可能会产生具有在各个组分相中不可用的特性的“新”材料，这也可能为设计具有不同寻常的交叉耦合特性的新纳米级结构开辟各种新的可能性。

著录项

  • 作者

    Wang, Yishu.;

  • 作者单位

    The University of Texas at Arlington.;

  • 授予单位 The University of Texas at Arlington.;
  • 学科 Materials science.;Plasma physics.
  • 学位 Ph.D.
  • 年度 2015
  • 页码 174 p.
  • 总页数 174
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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