Atomistic Control over Functional Defects in van der Waals Nanostructures

第1部分：非技术概述材料中的缺陷(缺陷)传统上被认为是不受欢迎的，特别是在半导体等电子材料中。因此，科学和工程领域的努力主要集中在消除技术应用材料中的缺陷。在材料研究部固体和材料化学项目的支持下，内布拉斯加州大学的Eli和Peter Sutter以及他们的团队寻求一种完全不同的方法，即(I)确定在材料合成过程中可能产生特定缺陷的机制；(Ii)确定控制其主体晶体中缺陷的位置和类型的方法；以及(Iii)揭示从此类受控缺陷中出现的特性。为了实现这一愿景，该项目专注于一类特殊的材料，即由弱范德华力连接在一起的原子薄片组成的层状晶体，以及一种“气-液-固”合成过程，该过程有望提供多种操纵单一缺陷的机会。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具有潜在的变革性影响。除了追求这些技术目标外，该项目还为参与的学生提供了影响深远的培训和职业发展机会。它旨在通过为来自内布拉斯加州农村社区的学生/教师团队组织年度暑期研讨会，并开发用于初中和高中科学课堂的基于微处理器的教具，来帮助提高教育、多样性和未被充分代表的群体--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。第二部分：技术概述传统上，电子和功能材料的缺陷被认为是有害的(因此是不受欢迎的)。最近的研究表明，点缺陷可能提供重要的新功能，例如用于量子信息处理。扩展缺陷可以类似地包含技术感兴趣的新特性，但从扩展缺陷中识别并最终利用功能面临重大挑战，包括开发具有对缺陷位置、取向和配置的固有控制的合成协议；以及在小宿主体积中定位定制的单个缺陷，从而使缺陷主导整体属性。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计划支持，通过利用范德华晶体对称性降低带来的机遇，开发气-液-固纳米结构生长工艺，结合电子结构、光电子学、电荷传输和铁电性等新特性的测量，对扩展的缺陷形成和调谐有一个基本的了解，从而解决这些挑战。具体地说，这项研究将审查层状单硫化物半导体及其合金的纳米结构中缺陷形成的材料化学，以及轴向和径向异质结构。它的目标是确定将定制的缺陷转录成广泛的其他材料的方法，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量身定做的单个线和平面缺陷的新特性奠定基础。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，在晶体材料中，新功能出现在具有受控属性的单一缺陷中。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.