In-situ and ex-situ STEM study of non-conventional line defects in perovskite oxides

钙钛矿氧化物中非常规线缺陷的原位和异位 STEM 研究

• 批准号: 2309431
• 负责人: Andre Mkhoyan
• 金额: $ 49.59万
• 依托单位: University of Minnesota-Twin Cities
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-06-01 至 2027-05-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2309431&HistoricalAwards=false
• 关键词: situ; ex; STEM; study; non

Non-Technical Summary The nanoscale materials present in electronic devices used every day should be engineered to make the devices smaller and increase their functions. To do this, new ways to harvest the properties of these materials should be found. One route is engineering atomic-level defects naturally present in these nanomaterials. While all crystalline nanomaterials have variety of defects in them, some defects are more promising than others. One dimensional defects, often referred to as line defects, are only a-few-atoms-wide and run along the entire crystal. This is an excellent opportunity to engineer them to get the properties wanted. Since they are only a-few-atoms-wide, they are intriguing objects embedded inside the main material, and they can have new and exciting properties that are unique to them. Study of these line defects requires ultra-high-resolution microscopes with features that can probe the properties of these defects. This project employs specialized analytical scanning transmission electron microscopes to study the identities, properties, and origins of these line defects. Combining these observations with theoretical predictions will provide additional flexibility when characterizing the defects. Perovskite oxide thin films have proven to be excellent hosts for such defects. The results will affect not only the science of defects in perovskite crystals, but also affect next-generation nanomaterial engineering by defect engineering. Within the framework of this project, high-school students will visit the University of Minnesota to have interactive tours of the Electron Microscopy Center at the Characterization Facility and see high-resolution electron microscopes in action. This outreach educational activity will be an academic-year-long program. Each year, groups of students and teachers from local high schools will participate in these tours, including schools with a considerable minority student population. Such a real-time dive into the structure of the materials and the operations of advanced electron microscopes should inspire students to pursue technical disciplines in college. It should also help teachers better convey to their students the science behind nanomaterials and microscopes using images obtained during their University of Minnesota visit. Technical SummaryAdvances over the past two decades have shown large numbers of materials can be scientifically exciting and technologically desirable when they have dimensions at the nanometer scale. Discoveries of new phenomena unique to nanoscale materials are being made almost daily, ranging from new physics—such as quantum transport of qubits in semiconductor nanowires or tetradymite chalcogenides being topological insulators—to new applications. Identifying the next frontiers in nanomaterials becomes more-and-more relevant. A new path for exciting new science and next-generation technology is possible through exploring and engineering the naturally-occurring defects in nanoscale materials, especially extended defects. These extended line (or 1D, dislocations and disclination, etc.) and planar (or 2D, grain boundaries, stacking faults, etc.) defects are particularly promising because they run across the entire crystal in one or two directions and are atomically small in other directions. Among them, line defects are only a-few-atoms-wide in two directions and extended in the third direction. With such natural geometry, it is expected that the properties of 1D defects should resemble a chain of atoms or a chain of single-unit cells. These defects should be rich with new physics and new quantum materials’ phenomena not seen in 2D materials. Nanostructures containing them could take advantage of both the features of the defect and the host. The study of new defects – understanding their properties and engineering them into new structures – is the main topic of this project, and it could be what is next in nanomaterials. Determining the effects of key factors (such as composition, strain, and temperature) on formation of line defects and their rearrangements in perovskite oxides are central aims of this work. Perovskite oxides (ABO3), are highly flexible and can accommodate various types of distortions, due to their complex structure. Such structural flexibility allows the perovskite host to accommodate unique extended defects, including those of different compositions. Thus, exploring such non-conventional defects in perovskite oxides has the potential to be extremely fruitful, largely expand the fundamental science of ceramic crystals, and transform next-generation nanomaterials. This study of non-conventional 1D line defects in perovskite oxides will be conducted ex-situ and in-situ using atomic-resolution, analytical scanning transmission electron microscopy (STEM) aided by density function tehroy (DFT) calculations.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

每天使用的电子设备中存在的纳米级材料应该被设计成使设备更小并增加其功能。要做到这一点，必须找到新的方法来获得这些材料的特性，一种方法是设计这些纳米材料中自然存在的原子级缺陷。虽然所有的晶体纳米材料都有各种各样的缺陷，但有些缺陷比其他缺陷更有前途。一维缺陷，通常称为线缺陷，只有几个原子宽，并沿沿着运行。这是一个很好的机会，工程师他们得到想要的属性。由于它们只有几个原子宽，它们是嵌入在主要材料中的有趣物体，并且它们可以具有独特的新的和令人兴奋的特性。这些线缺陷的研究需要超高分辨率显微镜的功能，可以探测这些缺陷的属性。这个项目采用专门的分析扫描透射电子显微镜来研究这些线缺陷的身份，属性和起源。将这些观察结果与理论预测相结合将在表征缺陷时提供额外的灵活性。过氧化氢薄膜已被证明是这种缺陷的优良宿主。这些结果不仅将影响钙钛矿晶体中缺陷的科学，而且还将通过缺陷工程影响下一代纳米材料工程。在该项目的框架内，高中生将访问明尼苏达大学，在表征设施的电子显微镜中心进行互动式图尔斯参观，并观看高分辨率电子显微镜的工作。这次推广教育活动将是一个为期一年的学术计划。每年，当地高中的学生和教师团体将参加这些图尔斯参观，包括少数民族学生人数较多的学校。这种对材料结构和先进电子显微镜操作的实时深入了解应该会激励学生在大学里追求技术学科。它还应该帮助教师更好地向学生传达纳米材料和显微镜背后的科学，使用他们在明尼苏达大学访问期间获得的图像。技术摘要过去二十年的进展表明，当大量材料具有纳米尺度时，它们在科学上令人兴奋，在技术上是可取的。几乎每天都有纳米级材料所特有的新现象被发现，从新物理（例如半导体纳米线中量子比特的量子传输或作为拓扑绝缘体的硅铍石硫属化合物）到新应用。确定纳米材料的下一个前沿变得越来越重要。通过探索和工程化纳米材料中自然发生的缺陷，特别是扩展缺陷，可以为令人兴奋的新科学和下一代技术开辟一条新的道路。这些延长线（或一维位错和向错等）和平面（或2D、晶界、堆垛层错等）缺陷是特别有希望的，因为它们在一个或两个方向上穿过整个晶体，并且在其它方向上是原子级小的。其中，线缺陷在两个方向上只有几个原子宽，并在第三个方向上延伸。有了这种自然的几何形状，预计1D缺陷的性质应该类似于原子链或单晶胞链。这些缺陷应该富含新的物理和新的量子材料的现象，在2D材料中看不到。含有它们的纳米结构可以利用缺陷和宿主的特征。对新缺陷的研究-了解它们的特性并将它们设计成新的结构-是该项目的主要主题，它可能是纳米材料的下一步。确定关键因素（如组成，应变和温度）对线缺陷的形成及其在钙钛矿氧化物中的重排的影响是这项工作的中心目标。过氧化氢氧化物（ABO 3）具有高度灵活性，由于其复杂的结构，可以适应各种类型的扭曲。这种结构灵活性允许钙钛矿主体适应独特的扩展缺陷，包括不同组成的缺陷。因此，探索钙钛矿氧化物中的这种非常规缺陷有可能非常富有成效，在很大程度上扩展了陶瓷晶体的基础科学，并改变了下一代纳米材料。这项钙钛矿氧化物中非常规一维线缺陷的研究将使用原子分辨率、分析型扫描透射电子显微镜（STEM）并辅以密度函数tehroy（DFT）计算进行非原位和原位研究。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。