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Transmission electron microscopy (TEM) is one of the key tools for direct structural characterization
of nano materials, thereby providing a basis for correlating synthesis conditions, structure and
physical properties. During the last 10 years, transmission electron microscopy has been
revolutionized by the advent of aberration correction providing true atomic resolution imaging of
materials and by combining imaging techniques with local analytical capabilities at the sub nanometer
length scale. In addition, with the tomographic techniques implemented, electron microscopy has
developed from a 2D projection technique to provide a full 3D view, giving new insights into the
structure of complex composite materials. The combination of all of these techniques in a single
instrument makes electron microscopy one of the most powerful techniques for structural
characterization of nano materials. Current developments in electron microscopy aim at further
expanding these possibilities to enable analysis of beam sensitive materials such as most organic
polymers and at combining the structural characterization with functional testing of nano materials in
in-situ experiments to directly image the structural changes e.g. during mechanical testing, heating or
with electron transport.
With this presentation, I will introduce state-of-the-art electron microscopy techniques, in particular
high-resolution imaging, nanoscale analysis and 3D electron tomography as well as a brief outlook on
in-situ techniques and will focus on the information that can be obtained with these approaches for
complex nano materials and how it helps to refine our understanding of the materials properties.
Examples will include self-assembled QD superlattices (Fig. 1) and nanoparticles formed by Janustype
molecules (Fig. 2) as well as catalysts, organic/nanoparticle hybrid LEDs and crystalline organic
polymers.
Figure 1: Tomographic reconstruction (volume
rendering) of the cubic CdS cluster packing and a
digital slice along the main crystallographic direction
of the superlattice revealing individual defects such
as dislocations and vacancies in 3D.
Figure 2: HRSTEM image revealing the POM
cluster ordering in a self-assembled
nanoparticle formed by a POM-C4-POSS
Janus-type molecule and the corresponding
3D electron tomographic reconstruction of the
phase separated honey-comb structure. |