Surface Termination and Shape Effects on Surface Induced Magnetism in Quantum Dots

技术概述：该项目由固态和材料化学计划支持，将利用量子点材料中的配体交换过程，在这些系统中诱导出有趣的新物理：即不使用化学掺杂剂的磁性。重点将放在针对可能导致量子点表面不成对电子的强场配体上。此外，还将研究颗粒形状对磁晶各向异性变化所产生的感生磁性的影响。利用同步辐射技术(X射线吸收、光电发射和圆二向色性)、磁学、电子自旋共振、光致发光、电子显微镜、紫外可见光谱和X射线衍射等多种材料表征技术，可以观察到配体场强和诱导磁性之间的关系。本课程将全面了解量子点上的配体交换化学，包括表面覆盖率和配体类型对交换过程的影响。量子点表面感应磁性的一般机制将导致新的量子点基磁性材料，这将导致基于紫外光激光器的新的磁光器件。非技术摘要：纳米磁性代表着纳米技术的新的潜在的市场应用，纳米技术是流行媒体热议的研究和技术领域。这一研究项目的突破可能导致更小、更高效的磁光材料。这个由固态和材料化学计划支持的项目将极大地增加我们对表面化学操纵如何在量子点中产生意想不到的和独特的磁性的理解。该项目将在包括磁光设备在内的技术部门找到现成的应用。这项研究将在表面科学与技术实验室(LASST)内进行，这是一个跨学科中心，汇集了来自物理、化学、电气与计算机工程和化学与生物工程的研究人员。该研究项目提供物理、化学和材料科学领域的高级研究生培训，特别是在特高压表面科学和磁学方面。该项目将利用美国国家科学基金会资助的缅因州物理科学伙伴关系，扩大到初中生和高中生。计划建立一个高级仪器本科生实验室，为工业界和学术界培养下一代物理学家、化学家、材料科学家和工程师。此外，将设在LASST的研究实验室将通过参观展出，并将向许多贫困学生介绍尖端工具，其中包括大量的美洲原住民。从仪器收集的信息将通过许多渠道传播，包括学术出版物和演示文稿，在UMaine网站上的描述，以及LASST和物理系的公开参观(许多中学学生和老师参加)。

TECHNICAL SUMMARY:This project, supported by the Solid State and Materials Chemistry program, will take advantage of ligand exchange processes in quantum dot materials to induce intriguing new physics in these systems: namely magnetism without the use of a chemical dopant. Focus will be placed on targeting strong-field ligands which can lead to unpaired electrons on the quantum dot surface. In addition, how the shape of the particle can affect the induced magnetism due to changes in magnetocrystalline anisotropy will be investigated. Using a host of materials characterization including synchrotron radiation techniques (x-ray absorption, photoemission, and circular dichroism), magnetometry, electron spin resonance, photoluminescence, electron microscopy, UV-Vis spectroscopy, and x-ray diffraction, correlations between ligand field strength and induced magnetism will be observed. A comprehensive understanding of ligand exchange chemistry on quantum dots, including surface coverage and effects of ligand type on exchange processes, will be obtained. The general mechanisms related to surface induced magnetism in quantum dots will lead to new quantum dot based magnetic materials which can lead to new magneto-optical devices based on UV lasers.NON-TECHNICAL SUMMARY:Nanomagnetism represents a new potential marketable use for nanotechnology, a field of research and technology heavily discussed by the popular media. Breakthroughs in this research venture could lead to smaller, more efficient magneto-optical materials. This project, supported by the Solid State and Materials Chemistry program, will greatly increase our understanding of how the manipulation of surface chemistry can lead to unexpected and unique magnetic properties in quantum dots. This project will find ready applications in technology sectors including magneto-optic devices. This research will take place within the Laboratory for Surface Science and Technology (LASST), an interdisciplinary center that brings together researchers from Physics, Chemistry, Electrical & Computer Engineering, and Chemical & Biological Engineering. This research program provides advanced graduate training in the fields of physics, chemistry, and materials science, and specifically in both UHV surface science and magnetometry. This project will leverage the NSF funded Maine Physical Sciences Partnership for outreach to both middle and high school students. An upper division undergraduate laboratory on advanced instrumentation is planned that will prepare the next generation of physicists, chemists, materials scientists, and engineers for both industrial and academic settings. In addition, the research laboratory, which will be housed in LASST, will be on display via tours and will introduce many underprivileged students, including a substantial Native American population, to cutting edge instrumental tools. Information collected from the instrumentation will be disseminated via many outlets, including academic publications and presentations, descriptions on UMaine websites, and public tours of LASST and the Physics Department (attended by many middle school students and teachers).