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Abstract
Electron microscopy is an invaluable tool to study the detailed structure of materials. Many of the analytical methods available in the transmission electron microscope, electron energy loss spectroscopy (EELS) in particular, provide detailed compositional and spectroscopic information with unprecedented spatial resolution. In today’s modern instruments, energy resolution down to 0.1eV with an electron beam approaching 0.1nm size is possible.
Various examples of applications of electron microscopy will be given in this presentation with results obtained with an ultrastable double aberration-corrected and monochromated electron microscope. First of all, we will demonstrate the detection of low-loss features in plasmonic nanostructures down to the infrared part of the electron energy loss spectrum by directly imaging resonances down to 0.5eV, the lowest features currently detected with EELS [1]. Using momentum resolved near-edge structures we will discuss the detection of the strong anisotropy in bonding in carbon nanotubes. After an overview of the imaging conditions used to detect ordering changes in alloy nanoparticles using a combination of X-ray diffraction techniques and high-angle annular dark-field STEM imaging and simulations, we will discuss the application of atomic-resolved EELS mapping in the study of interfaces [2,3]. We will demonstrate how this powerful technique can be used in the study of the structure and substitutional effects on the atomic structure of interfaces and electronic states changes within one or two unit cells from the interface. We will demonstrate how such spectroscopic technique can be used to detect changes in valence and electronic structure as well as the termination of substrate surfaces in contact with epitaxial films. Examples will show how the stability of microscopes, coupled with atomic resolution, can be used to not only obtain spectroscopic information but also to determine, directly from HAADF images, the local strain at interfaces and at dislocations [4]. Additional examples will highlight the application of microscopy technique to the analysis of clusters, multiferroic materials based on the perovskite structures, and interfaces in complex oxides. These examples demonstrate that compositional and chemical state (valence and coordination) information can be obtained down to the Ångstrom level even on surfaces[5].
[1] D. Rossouw, et al., Nano Letters 11, 1499-1504 (2011)
[2] G.A. Botton, et al. Ultramicroscopy, 110, 926- 934, (2010)
[3] S. Lazar, et al., Microscopy and Microanalysis, 16, 416-424, (2010).
[4] S. Hosseini et al., Applied Physics Letters 98, 082113 (2011)
[5] G.-Z. Zhu, G. Radtke, G.A. Botton, Nature, doi:10.1038/nature11563 (10 Oct 2012)
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