MRI: Development of a Localized Field Emission Scanning Electron Microscope and Secondary Electron Spin Polarization Analysis System

主要研究仪器奖支持开发一种新型的经济高效的电子显微镜，该显微镜能够以高空间分辨率对表面的顶层进行成像。该项目的范围是将扫描电子（SEM）和扫描探针显微镜（SPM）的基本概念结合到一个称为“近场发射扫描电子显微镜”（NFESEM）的仪器中。使用低能电子NFESEM将对许多领域产生影响，包括生物、医疗、数据存储、计算和可再生能源。该设备将立即为新泽西州和宾夕法尼亚州东部的研究人员提供另一种高分辨率的表面成像设备。这个项目的结果将被纳入新泽西学院的课程。参与该项目的本科生将接受培训并获得这些技术方面的专业知识。该仪器将有助于支持即将到来的技术发展，特别是在超大规模集成电路和自旋电子学领域。此外，包括早期职业和成熟的科学家和工程师在内的合作计划将影响超导，低能电子能谱，纳米器件表征，纳米颗粒药物输送等方面的研究。工业伙伴的参与将加强培训和知识转让。研究人员还将以此为契机，向来自特伦顿的未被充分代表的中学生和高中生介绍基本的显微镜及其应用。NFESEM将提供一种克服传统扫描电子显微镜（SEM）局限性的方法，并开启了使用更低初级光束能量（100 eV）的可能性。本质上，NFESEM是一种中间技术，其中电子通过场电子发射从针尖发射，然后撞击样品并与样品相互作用。结果，电子从样品表面射出并被检测，电子自旋探测器将被纳入系统中，用于对射出的二次电子进行极化分析。与自旋极化仪相结合的fesem将使具有极化分析能力的SEM能够进行纳米磁成像，特别是低维磁系统。该显微镜将配备无低温电磁体，该电磁体可以用高达3000高斯的磁场磁化感兴趣的样品。设计和控制单元添加到扫描探针显微镜将允许高速成像，这是必不可少的模拟标准扫描电子显微镜的成像能力。显微镜独特的工作方式，配合偏光计，产生三个特征信号：1)场发射电流；2)背散射和二次电子信号的变化；3)三维表面自旋不对称性。该集成将使磁性材料的纳米成像成为可能；特别是低维磁系统。NFESEMPA将是同类中的第一个，提议的研究小组将能够确定使用无透镜扫描电子显微镜的优点和/或缺点，c.f.当代SEMPA。因此，本项目将提出一种替代方法来产生精细电子束，用于原子“光滑”表面的高分辨率成像。

The Major Research Instrumentation award supports the development of a novel cost-efficient electron microscope capable of imaging the top-most layers of surfaces with high spatial resolution at the College of New Jersey. The scope of the project is to combine the fundamental concepts of scanning electron (SEM) and scanning probe microscopies (SPM) into a single instrument called "Near Field Emission Scanning Electron Microscopy" (NFESEM). The use of low energy electrons NFESEM will have an impact over many areas including biological, medical, data storage, computing and renewable energy. The device will immediately provide an alternative, high resolution surface imaging device to researchers in both New Jersey and Eastern Pennsylvania. The results from this project will be incorporated in course curricula at The College of New Jersey. Undergraduate students involved in the project will be trained and acquire expertise in these techniques. The instrumentation will help underpin forthcoming technological developments especially in the area of ultra large scale integrated circuits and spintronics. Furthermore, the collaboration scheme which includes early career and well-established scientists and engineers will impact research on superconductivity, low energy electron spectroscopy, nano-device characterization, nanoparticle enabled drug delivery and more. Involvement of industrial partners will enhance the training and transfer of knowledge. The researchers will also use this as an opportunity to introduce underrepresented middle school and high school students from Trenton to basic microscopy and its applications.NFESEM will provide a means of overcoming the limitations of conventional scanning electron microscopes (SEM) and opens the possibility to use lower primary beam energies ( 100 eV). In essence, NFESEM is an intermediate technique in which electrons are emitted from a needle tip via field electron emission, and then impinge on and interact with the sample. As a result, electrons are ejected from the sample surface and detected and an electron spin detector will be incorporated into the system for polarization analysis of ejected secondary electrons. The NFESEM coupled with a spin polarimetry will enable SEM with polarization analysis capable of nanometer magnetic imaging, in particular low dimensional magnetic systems. The microscope will be equipped with a cryogen-free electro-magnet that is constructed to magnetize the sample of interest with a magnetic field up to 3,000 Gauss. The design and the control unit added to the scanning probe microscope will allow for high speed imaging, which is essential to simulate the imaging capabilities of standard scanning electron microscopes. The unique operating mode of the microscope, coupled with the polarimeter, generates three characteristic signals: 1) field emission current; 2) variations in the backscattered and secondary electron signal; and 3) a three dimensional surface spin asymmetry. This ensemble will enable nanometric imaging of magnetic materials; in particular, low dimensional magnetic systems. The NFESEMPA will be the first of its kind, and the proposed research team will be able to determine the advantages and/or disadvantages of using lensless scanning electron microscopy, c.f. contemporary SEMPA. Accordingly, this project will present an alternative method to generate a fine electron beam for high resolution imaging of atomically "smooth" surfaces.