MRI: Acquisition of an Imaging Spherical Aberration Corrector and a Lorentz Lens for Magnetic Materials Characterization

技术摘要：在洛伦兹透射电子显微镜中，高能电子束穿过磁性薄片，通过聚焦成像分析洛伦兹力引起的偏转。由于低场洛伦兹极片具有较大的球差系数，未经校正的洛伦兹仪器的空间分辨率可达10-15 nm。此外，去局部化效应会导致严重的图像模糊，这使得定量测量非常具有挑战性。在像差校正方面的最新进展使将洛伦兹透镜的球差校正到足以抑制离域效应的值成为可能，从而为研究材料的磁性纳米结构打开了一个全新的观察窗口。在这份MRI提案中，我们申请资金用于购买成像球差校正器和用于磁性材料表征的洛伦兹透镜；这些部件将被添加到现有的FEI Titan 80-300透射电子显微镜中。校正器和洛伦兹透镜是满足日益增长的磁性材料表征要求的关键。例如，在现有的磁记录介质中，写入比特的大小与未经校正的洛伦兹显微镜的磁分辨率相当，因此几乎不可能获得磁微结构的高分辨率洛伦兹图像。Lorentz透镜和专用校正器的组合将使Lorentz模式的空间分辨率降至低于1 nm，而离域效应可以忽略不计，从而首次能够在约1 nm的长度尺度上直接定量研究磁性特征。我们预计，将在以前不可能进行这些观测的物质系统上获得大量新的科学结果。校正器和洛伦兹透镜的可获得性将影响CMU内的大量研究小组，以及与当地工业和几个国家实验室的合作。通过将矫正人员培训课程与现有的瞬变电磁学课程相结合，我们将加强对本地和远程学生的高级TM教育。非技术摘要：自20世纪30年代发明以来，透射式电子显微镜一直遭受透镜像差的影响，类似于哈勃太空望远镜首次发射时的像差；这些仪器获得的图像是模糊的，而不是清晰的，因此很难提取有关被研究对象的可靠信息。哈勃望远镜通过增加一个矫正透镜(基本上是一副矫正眼镜)进行了修复，最近，这种眼镜也可以用于电子显微镜。在这份核磁共振提案中，我们申请资金为卡内基梅隆大学现有的电子显微镜购买校正光学元件，以及使我们能够研究具有非常高空间分辨率的磁性材料的特殊透镜。磁性材料在当今社会的许多方面都很重要，特别是在磁性硬盘驱动器上的数据存储方面。硬盘驱动器上的单个数据位非常小，以至于目前的电子显微镜无法获得它们的清晰图像。然而，使用校正器，将有可能以前所未有的清晰度研究这些比特；这些观察反过来将导致可存储在硬盘上的信息密度的进一步提高，以及长期存储的可靠性。矫正光学将允许对目前不可能进行这些观测的材料产生大量新的科学结果。矫正光学设备的可获得性将影响CMU内的大量研究小组，以及与当地行业和几个国家实验室的合作。通过将校正员培训课程与现有的电子显微镜课程相结合，我们将加强对本地和远程学生的先进材料表征方法的教育。

Technical Abstract:In Lorentz transmission electron microscopy, a high-energy electron beam is directed through a magnetic thin foil and the deflections caused by the Lorentz force are analyzed by means of through-focus imaging. The attainable spatial resolution of uncorrected Lorentz instruments is in the range 10-15 nm, due to the large spherical aberration coefficient of the low field Lorentz pole piece. In addition, delocalization effects cause significant image blurring, making quantitative measurements very challenging. Recent developments in aberration correction make it possible to correct the spherical aberration of a Lorentz lens to a value which is sufficiently small to suppress delocalization effects, thereby opening up a completely new observation window on the magnetic nanostructure of materials. In this MRI proposal, we request funding for the acquisition of an imaging spherical aberration corrector and a Lorentz lens for magnetic materials characterization; these components will be added to an existing FEI Titan 80-300 TEM. The corrector and Lorentz lens are crucial to meet the increasing demands of magnetic materials characterization. In state-of-the-art magnetic recording media, for instance, the size of the written bits is comparable to the magnetic resolution of uncorrected Lorentz microscopes, so that it is nearly impossible to obtain high resolution Lorentz images of the magnetic microstructure. The combination of a Lorentz lens and a dedicated corrector will bring the spatial resolution in Lorentz mode down to less than 1 nm, with negligible delocalization effects, thereby enabling for the first time the direct quantitative study of magnetic features at a length scale of around 1 nm. We anticipate that a large number of new scientific results will be obtained on material systems for which these observations were previously impossible. The availability of a corrector and Lorentz lens will impact a large number of research groups within CMU, as well as collaborations with local industry and several national laboratories. Through integration of the corrector training sessions with an existing course on TEM, we will strengthen the education of local and remote students in advanced TEM.Non-Technical Abstract:Since their invention in the 1930s, transmission electron microscopes have suffered from a lens aberration, similar to the aberration suffered by the Hubble space telescope when it was first launched; the images acquired in these instruments are blurred instead of sharp, so that it is difficult to extract reliable information about the objects being studied. The Hubble telescope was repaired by the addition of a corrector lens (essentially a pair of corrective glasses), and, recently, such glasses have also become available for electron microscopes. In this MRI proposal, we request funding for the acquisition of corrector optics for an existing electron microscope located at Carnegie Mellon University, along with a special lens that will enable us to study magnetic materials with very high spatial resolution. Magnetic materials are important in many aspects of today's society, in particular in data storage on magnetic hard drives. The individual data bits on a hard drive are so small, that current electron microscopes cannot obtain sharp images of them. Using the corrector, however, it will become possible to study these bits with an unprecedented clarity; these observations, in turn, will result in further improvements in the density of information that can be stored on a hard disk, and in the reliability of long-term storage. The corrective optics will allow for the generation of a large number of new scientific results on materials for which these observations are currently impossible. The availability of the corrective optics will impact a large number of research groups within CMU, as well as collaborations with local industry and several national laboratories. Through integration of the corrector training sessions with an existing course on electron microscopy, we will strengthen the education of local and remote students in advanced materials characterization methods.