Synthesis and Properties of Heterostructures Containing Magnetic 2d Layers Not Found As Bulk Compounds

含有未发现为本体化合物的磁性二维层的异质结构的合成和性能

• 批准号: 2219512
• 负责人: David Johnson
• 金额: $ 45万
• 依托单位: University of Oregon Eugene
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-09-01 至 2025-08-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2219512&HistoricalAwards=false
• 关键词: Synthesis; Properties; Heterostructures; Containing; Magnetic

NON-TECHNICAL SUMMARYThe 2010 Nobel prize in physics was awarded for the discovery of novel properties in monolayers of compounds with two dimensional (2D) structures that are not present in the bulk compounds. The resulting field of science - 2D materials and stacked layers of 2D materials known as heterostructures - has exponentially expanded as theorists proposed new exotic properties and experimentalists discovered new properties in monolayers and heterostructures. Currently the preparation of heterostructures is done by cleaving bulk materials to the monolayer limit and stacking them in designed sequences. This approach is limited to constituents that are stable as bulk compounds which are cleavable. New synthesis approaches are needed that enable preparation of heterostructures at a wafer scale, that provide a wider selection of constituent layers, and that provide control over the nanoarchitecture (stacking sequence and thickness of constituent layers). In this project, with the support of the Solid State and Materials Chemistry and Ceramics Programs in the Division of Materials Research, Dr. David Johnson and his research group at the University of Oregon, will develop new synthetic approaches to preparing heterostructures containing 2D magnetic constituent layers with structures and compositions that are not thermodynamically stable as isolated compounds. Three different strategies, all of which use precursors with targeted composition profiles that match that of the targeted heterostructures, are being tested. This research program provides a broad technical background for graduate students in deposition technologies, thin film characterization techniques, and physical phenomena that occur in 2D heterostructures. This training enables them to thrive in a variety of future careers (high tech industries, academia, or national laboratories). Internships will provide an opportunity for graduate students to “test drive” future careers while expanding their knowledge base, leading to more productive researchers. Engaging undergraduate students in this research enables them to apply principles learned in classes to solve research challenges. Providing undergraduate research opportunities is a critical tool to increase the number and diversity of students pursuing science as a career. TECHNICAL SUMMARYWith the support of the Solid State and Materials Chemistry and Ceramics Programs in the Division of Materials Research, Dr. David Johnson and his research group at the University of Oregon will develop synthetic approaches to preparing heterostructures containing 2D magnetic constituent layers with structures and compositions that are not thermodynamically stable as isolated compounds. Synthetic targets include diselenides (TSe2) and rock salt structured Pb2+nT1+mSe3+n+m layers, where T = Cr, Mn, Fe and Ni. Three synthesis strategies, which use precursors with targeted local composition and nanoarchitecture to control nucleation and growth, are being tested. One strategy is to prepare a precursor designed such that one layer crystalizes as 2D sheets separated by amorphous layers of controlled composition. The resulting 2D form factor and composition of the interleaved amorphous layers as well as the structure of adjacent crystalline layers will be used to control the nucleation and growth of the metastable constituent layers. A second strategy will be to seed nucleation of the desired structures by controlling local composition. A third strategy will be to use charge transfer from an adjacent layer to stabilize the targeted structures. The companion constituents in the targeted heterostructures will be critical to controlling the reaction pathways for each of these strategies, and our list of potential constituents include piezoelectric (GeSe, SnSe), topological insulating (Bi2Se3, Bi2Te3), semiconducting (PbSe, MoSe2, SnSe2) and/or superconducting (NbSe2) layers. A rich collection of new materials with diverse and tunable emergent properties is anticipated.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.

2010年诺贝尔物理学奖授予了在具有二维（2D）结构的化合物单层中发现的新颖性质，这些性质在本体化合物中不存在。由此产生的科学领域- 2D材料和被称为异质结构的2D材料的堆叠层-随着理论家提出新的奇异特性和实验学家发现单层和异质结构的新特性而呈指数级扩展。目前，异质结构的制备是通过将大块材料切割到单层极限并将它们以设计的顺序堆叠来完成的。该方法限于作为可裂解的本体化合物稳定的成分。需要新的合成方法，其能够在晶片级制备异质结构，提供更广泛的组成层选择，并且提供对纳米结构（组成层的堆叠顺序和厚度）的控制。 在该项目中，在材料研究部的固态和材料化学与陶瓷计划的支持下，大卫约翰逊博士和他在俄勒冈州大学的研究小组将开发新的合成方法来制备含有2D磁性组成层的异质结构，其结构和成分作为孤立的化合物是不稳定的。正在测试三种不同的策略，所有这些策略都使用具有与目标异质结构相匹配的目标组合物概况的前体。 该研究计划为研究生提供了广泛的技术背景，包括沉积技术，薄膜表征技术和2D异质结构中发生的物理现象。这种培训使他们能够在各种未来的职业生涯（高科技行业，学术界或国家实验室）蓬勃发展。实习将为研究生提供一个“试驾”未来职业的机会，同时扩大他们的知识基础，从而培养出更有成效的研究人员。让本科生参与这项研究使他们能够应用课堂上学到的原则来解决研究挑战。提供本科研究机会是增加追求科学作为职业的学生数量和多样性的关键工具。 技术总结在材料研究部的固态和材料化学与陶瓷计划的支持下，俄勒冈州大学的大卫约翰逊博士和他的研究小组将开发制备异质结构的合成方法，该异质结构包含结构和组成不稳定的2D磁性成分层。合成目标包括二硒化物（TSe 2）和岩盐结构的Pb 2 + nT 1 + mSe 3 +n+m层，其中T = Cr、Mn、Fe和Ni。正在测试三种合成策略，即使用具有目标局部组成和纳米结构的前体来控制成核和生长。一种策略是制备设计成使得一层结晶为由受控组成的无定形层分离的2D片材的前体。所得到的交错非晶层的2D形状因子和组成以及相邻结晶层的结构将用于控制亚稳构成层的成核和生长。第二种策略是通过控制局部成分来为所需结构的成核提供种子。第三种策略是使用来自相邻层的电荷转移来稳定目标结构。目标异质结构中的伴随成分对于控制这些策略中的每一个的反应途径将是至关重要的，并且我们的潜在成分列表包括压电（GeSe、SnSe）、拓扑绝缘（Bi 2Se 3、Bi 2 Te 3）、半导体（PbSe、MoSe 2、SnSe 2）和/或超导（NbSe 2）层。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。