Atomistic Control over Functional Defects in van der Waals Nanostructures

第一部分：材料中的缺陷（缺陷）传统上被视为不期望的，特别是在电子材料如半导体中。因此，科学和工程领域的努力集中在消除技术应用材料中的缺陷上。在材料研究部的固态和材料化学项目的支持下，教授们。内布拉斯加大学的Eli和Peter Sutter及其团队追求一种根本不同的方法，即（i）确定在材料合成过程中产生特定缺陷的可能机制;（ii）确定控制其宿主晶体中缺陷的位置和类型的方法;（iii）揭示这种受控缺陷的性质。为了实现这一愿景，该项目专注于一类特殊的材料，即由弱货车德瓦尔斯力结合在一起的原子级薄片组成的层状晶体，以及一种“气-液-固”合成工艺，该工艺有望为操纵单一缺陷提供多种机会。如果成功，这项研究可能会从根本上改变我们对电子材料缺陷的看法，对基础科学和关键技术领域产生潜在的变革性影响。除了追求这些技术目标外，该项目还为参与的学生提供了广泛的培训和职业发展机会。它的目的是帮助提高教育、多样性和代表性不足的群体--特别是来自农村和美洲土著部落社区的女孩--在科学、技术、工程和数学（STEM）方面的参与，方法是为内布拉斯加州农村社区的学生/教师团队组织年度夏季讲习班，并开发基于微处理器的教具，供初中和高中科学教室使用。在电子和功能材料中，缺陷传统上被认为是有害的（因此是不希望的）。最近的研究表明，点缺陷可以提供重要的新功能，例如，用于量子信息处理。扩展缺陷同样可以隐藏技术感兴趣的新兴特性，但识别并最终利用扩展缺陷的功能面临着重大挑战，包括开发对缺陷放置，方向和配置具有先天控制的合成协议;以及在小主机体积中定位定制的单个缺陷，以便缺陷主导整体特性。 该项目由美国国家科学基金会材料研究部的固态和材料化学项目支持，通过利用货车德瓦尔斯晶体对称性降低所带来的机会，并通过开发气-液-固纳米结构生长过程来解决这些挑战，以获得对扩展缺陷形成和调整的基本理解，并结合新兴特性的测量，如电子结构，光电子学、电荷传输和铁电性。具体而言，该研究将研究分层单硫族化物半导体，其合金以及轴向和径向异质结构的纳米结构中的位错和堆垛层错等缺陷形成的材料化学。它的目标是确定将定制缺陷转录到各种其他材料中的方法，包括其他层状晶体和传统的3D晶体半导体。这将为系统地探索各种纳米结构材料中定制的单个线和平面缺陷的新兴特性奠定基础。该项目目标的成功实现可能为追求晶体材料的范式转变铺平道路，其中新的功能从具有受控特性的单一缺陷中产生。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Part 1: Non-Technical Summary Imperfections (defects) in materials have traditionally been seen as undesirable, especially in electronic materials such as semiconductors. Hence, efforts in science and engineering have focused on eliminating defects in materials for technological applications. With support from the Solid State and Materials Chemistry program in the Division of Materials Research, Profs. Eli and Peter Sutter and their groups at the University of Nebraska pursue a fundamentally different approach, namely to (i) identify possible mechanisms by which specific defects can be generated during materials synthesis; (ii) determine ways of controlling the placement and type of the imperfection in its host crystal; and (iii) uncover the properties emerging from such controlled defects. To realize this vision, the project focuses on a particular class of materials, layered crystals consisting of atomically thin sheets held together by weak van der Waals forces, as well as a "vapor-liquid-solid" synthesis process that promises manifold opportunities for manipulating single defects. If successful, the research could fundamentally change our view of defects in electronic materials, with potentially transformative impact in basic science as well as key sectors of technology. In addition to pursuing these technical objectives, the project provides far-reaching opportunities for training and career development to the participating students. And it aims to help enhance education, diversity, and the participation of underrepresented groups – in particular girls from rural and Native American tribal communities – in Science, Technology, Engineering, and Math (STEM) by organizing annual summer workshops for student/teacher teams from rural Nebraska communities and by developing microprocessor-based teaching aids for use in middle- and high school science classrooms.Part 2: Technical SummaryDefects have traditionally been perceived as detrimental (and thus undesirable) in electronic and functional materials. Recent research showed that point defects may provide important new functionality, e.g., for quantum information processing. Extended defects could similarly harbor emerging properties of interest for technology, but identifying and ultimately harnessing functionality from extended defects faces major challenges, including the development of synthesis protocols with innate control over defect placement, orientation, and configuration; and the positioning of tailored single defects in a small host volume so that the defect dominates the overall properties. This project supported by the Solid State and Materials Chemistry program in the NSF’s Division of Materials Research addresses these challenges by taking advantage of opportunities presented by the reduced symmetry of van der Waals crystals and by developing vapor-liquid-solid nanostructure growth processes to obtain a fundamental understanding of extended defect formation and tuning combined with measurements of emerging properties such as electronic structure, optoelectronics, charge transport, and ferroelectricity. Specifically, the research will examine the materials chemistry underlying the formation of defects such as dislocations and stacking faults in nanostructures of layered monochalcogenide semiconductors, their alloys, as well as axial and radial heterostructures. And it aims to identify approaches for transcribing tailored defects into a wide range of other materials, including other layered crystals and conventional 3D-crystalline semiconductors. This will set the stage for systematically exploring the emerging properties of tailored individual line and planar defects in a wide range of nanostructured materials. The successful realization of the project goals could pave the way for a paradigm shift toward the pursuit of crystalline materials where new functionality emerges from single defects with controlled properties.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.