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，高能电子束通过磁性薄片，通过聚焦成像分析了洛伦兹力引起的偏转。由于低场洛伦兹极片的球差系数较大，未校正洛伦兹仪器可获得的空间分辨率在10 ~ 15 nm范围内。此外，离域效应会导致显著的图像模糊，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得将洛伦兹透镜的球差校正到足够小的值以抑制离域效应成为可能，从而打开了一个全新的观察材料磁性纳米结构的窗口。在这个MRI提案中，我们请求资助购买成像球差校正器和用于磁性材料表征的洛伦兹透镜；这些组件将被添加到现有的FEI泰坦80-300 TEM上。校正器和洛伦兹透镜对于满足磁性材料表征日益增长的需求至关重要。例如，在最先进的磁记录介质中，写入比特的大小与未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性微观结构的高分辨率洛伦兹图像。洛伦兹透镜和专用校正器的结合将使洛伦兹模式下的空间分辨率降至1 nm以下，而离域效应可以忽略，从而首次实现了在1 nm左右的长度尺度上对磁性特征的直接定量研究。我们预计，在以前不可能观测到的物质体系上，将获得大量新的科学结果。校正器和洛伦兹透镜的可用性将影响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。通过将校对员培训课程与现有的TEM课程相结合，我们将加强对本地和偏远地区学生的高级TEM教育。摘要：自20世纪30年代发明以来，透射电子显微镜一直存在透镜像差，类似于哈勃太空望远镜首次发射时所遭受的像差；在这些仪器中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。哈勃望远镜是通过增加一个校正透镜（本质上是一副校正眼镜）来修复的，最近，这种眼镜也可以用于电子显微镜。在这个MRI提案中，我们请求资助为卡内基梅隆大学现有的电子显微镜购买校正光学器件，以及一个特殊的透镜，使我们能够以非常高的空间分辨率研究磁性材料。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。硬盘上的单个数据位是如此之小，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；这些观察结果反过来又会进一步提高存储在硬盘上的信息密度和长期存储的可靠性。校正光学将允许在材料上产生大量新的科学结果，而目前这些观测是不可能的。校正光学的可用性将影响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.