When 3:30 PM - 5:00 PM Jan 20, 2012
Where 1670 CSE Building
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Electron Microscopy: An Essential Tool for the Study of Nanoscale Materials


Gianluigi Botton
McMaster University, Materials Science and Engineering

Nanoscale materials are the building blocks of nanoscience and nanotechnology. In order to better understand the structure and composition of materials with nanometer scale dimensions, new tools with high spatial resolution and sensitivity need to be used.  Electron microscopy is an invaluable tool that provides imaging capabilities with atomic resolution while providing spectroscopic sensitivity to probe the chemical state of elements in the sample. In today’s modern electron microscopes, synchrotron quality spectra with 0.1eV resolution can be achieved using an electron beam approaching 0.1nm size.

 

An overview of various examples of applications of electron microscopy will be given in this presentation with results obtained using an aberration-corrected and monochromated electron microscope. First of all, we will demonstrate the detection of low energy-loss features in plasmonic nanostructures down to the infrared part of the electron energy loss spectrum by directly imaging resonances down to 0.5eV and below, the lowest features currently detected with electron energy loss spectroscopy (EELS) [1]. After an overview of the imaging conditions used to detect ordering changes in alloy nanoparticles and in graphene-based fuel cell materials using a combination of X-ray diffraction techniques and transmission electron microscopy, 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 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 and even in the third dimension[5-6].

 

[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] F. Nan, et al. , Chemcatchem, 3, 999-1003, (2011).

[6] M. Couillard, et al., Physical Review Letters, 107, 186104, (2011).

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