CAREER: Van der Waals-mediated epitaxy of Heusler compounds through properties-selective, atomically thin barriers

现代电子学依赖于晶体半导体材料之间精确控制的界面。实现这一目标仍然是一个挑战。该项目由材料研究部固态与材料化学项目支持，从根本上研究了制造磁性材料界面的新方法，并在尽可能小的长度尺度（原子分辨率）下控制它们。该项目专注于一类被称为Heusler化合物的材料，探索单晶在原子薄势垒材料上生长的机制。并对这些材料在高能效磁性和热电器件中的应用进行了测试。研究工作与中学生的课后讲习班相结合。“从原子到iPhone：材料科学及其在日常生活中的应用”是一个研讨会，通过智能手机这一常见应用的镜头，吸引年轻学生参与材料科学和工程主题。首席研究员和他的团队在戴恩县男孩女孩俱乐部开展SCIENCountErs项目。该项目由材料研究部固态和材料化学项目支持，旨在发现和开发全新的方法来控制离子、电荷和自旋在Heusler界面上的传输。Heusler化合物长期以来一直被认为是半导体自旋电子学的理想材料，也是发现和操纵物质拓扑量子态的平台。然而，通过Heusler/半导体界面的相互扩散抑制了这些实现，因为需要原子锋利和稳定的外延界面。该项目通过使用原子薄的势垒材料（如石墨烯）来解决这些挑战，其中势垒材料充当(1)扩散势垒，(2)薄膜和衬底之间外延排列的透明去耦层，以及(3)有效电荷和自旋在界面上传输的隧道势垒。通过将分子束外延（MBE）高度可控的Heusler合成与原位光谱工具相结合，模型实验被用来揭示范德华介导外延的机制，并开发出原子控制的Heusler界面制造方法。来自研究部分的基本见解被整合到“原子到iPhone”研讨会的现实生活演示中，并被整合到主要研究者教授的本科和研究生课程中。本科生和研究生的第一手研究经验为STEM和相关领域的职业生涯提供了一个训练基地。该奖项反映了美国国家科学基金会的法定使命，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。

Non-technical summary Modern electronics rely on precisely controlled interfaces between crystalline semiconducting materials. Achieving this remains a challenge. This project, supported by the Solid State and Materials Chemistry Program in the Division of Materials Research, researches fundamentally new ways to fabricate such interfaces of magnetic materials and control them at the smallest length scale possible (atomic resolution). Focusing on a class of materials called Heusler compounds, the project explores the mechanisms for single-crystalline growth on atomically thin barrier materials. Application of these materials in energy-efficient magnetic and thermoelectric devices is also tested. The research efforts are integrated with an after-school workshop for middle-school students. "From atoms to iPhone: the science of materials and their applications in everyday life." is a workshop that engages young students in materials science and engineering topics through the lens of a common application, the smartphone. The principle investigator and his group carry out work with the SCIENCountErs program at the Boys and Girls Club of Dane County on this. Technical summaryThis project is supported by the Solid State and Materials Chemistry Program in the Division of Materials Research and aims to uncover and develop fundamentally new ways to control the transmission of ions, charge, and spins across Heusler interfaces. Heusler compounds have long been proposed as ideal materials for semiconductor spintronics and a platform for discovery and manipulation of topological quantum states of matter. However, interdiffusion across the Heusler/semiconductor interface has inhibited these realizations, since atomically sharp and stable epitaxial interfaces are required. This project addresses these challenges through the use atomically thin barrier materials such as graphene, where the barrier material serves as (1) a diffusion barrier, (2) a transparent decoupling layer for epitaxial alignment between film and substrate, and (3) a tunnel barrier for efficient charge and spin transport across the interface. By pairing highly controlled Heusler synthesis by molecular beam epitaxy (MBE) with in-situ spectroscopic tools, model experiments are being used to reveal the mechanisms for Van der Waals-mediated epitaxy and develop methods for the atomically controlled fabrication of Heusler interfaces. Fundamental insights from the research component are integrated into real life demonstrations for the "Atoms to iPhone" workshop and integrated into undergraduate and graduate courses taught by the principle investigator. First hand research experiences for undergraduate and graduate students provide a training ground for careers in STEM and related fields.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.