Electron Holography of Magnetic Materials
Electron Holography of Magnetic Materials
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DOI：
10.5772/22366
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发表时间：
2011-09
期刊：
影响因子：
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通讯作者：
T. Kasama;R. Dunin‐Borkowski;M. Beleggia
中科院分区：
文献类型：
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作者：
T. Kasama;R. Dunin‐Borkowski;M. Beleggia
透射式电子显微镜(TEM)使用高能(60-3000 keV)电子穿过薄样品，记录感兴趣区域的图像、衍射图或光谱信息。多年来，许多不同的瞬变电磁技术已经发展成高度复杂的方法，并在科学学科中得到了广泛的应用。由于透射电子显微镜具有无与伦比的能力，可以提供从一系列长度尺度到原子维度的结构和化学信息，它已经发展成为对了解纳米结构材料的性质和操纵它们的行为感兴趣的科学家不可或缺的工具(Smith，2007)。最先进的TEM现在配备了球面和色差校正器，可以提供0.05纳米的可解释图像分辨率(Erni等人，2009年)。然而，除了可以用来提供材料结构和组成信息的传统透射电子显微镜技术外，透射电子显微镜还允许以纳米空间分辨率成像样品中的磁场和静电场。提供这种信息的最强大的技术之一是电子全息术，它最初是作为一种补偿透镜像差和提高电子显微镜分辨率的手段提出的(Gabor，1949)。电子全息术仍然是唯一一种可以直接获得穿过薄样品的电子波相移的技术，与更传统的只记录图像强度空间分布的电子全息技术形成鲜明对比。电子全息术直到最近才在商用电子显微镜上得到广泛应用。早期使用电子全息术的研究受到用作电子源的钨丝的有限亮度和相干性的限制(Haine&Mulvey，1952)。高亮度、稳定、相干的场发射电子枪的出现使得电子全息术可以应用于各种材料，如量子井结构、磁性薄膜、半导体器件、天然岩石和生物矿物。
Transmission electron microscopy (TEM) involves the use of high-energy (60-3000 keV) electrons that have passed through a thin specimen to record images, diffraction patterns or spectroscopic information from a region of interest. Many different TEM techniques have been developed over the years into highly sophisticated methodologies that have found widespread application across scientific disciplines. Because the TEM has an unparalleled ability to provide structural and chemical information over a range of length scales down to atomic dimensions, it has developed into an indispensable tool for scientists who are interested in understanding the properties of nanostructured materials and in manipulating their behavior (Smith, 2007). State-of-the-art TEMs are now equipped with spherical and chromatic aberration correctors and can provide interpretable image resolutions of 0.05 nm (Erni et al., 2009). However, in addition to conventional TEM techniques that can be used to provide structural and compositional information about materials, the TEM also allows magnetic and electrostatic fields in specimens to be imaged with nanometer spatial resolution. One of the most powerful techniques for providing this information is electron holography, which was originally proposed as a means to compensate for lens aberrations and to improve electron microscope resolution (Gabor, 1949). Electron holography is still the only technique that provides direct access to the phase shift of the electron wave that has passed through a thin specimen, in contrast to more conventional TEM techniques that record only spatial distributions of image intensity. Electron holography has only recently become widely available on commercial electron microscopes. The earliest studies using electron holography were restricted by the limited brightness and coherence of the tungsten filaments that were used as electron sources (Haine & Mulvey, 1952). The availability of high brightness, stable, coherent field emission electron guns now allows electron holography to be applied to a wide variety of materials such as quantum well structures, magnetic thin films, semiconductor devices, natural rocks and biominerals.