The Hitachi 2700C is a dedicated Scanning Transmission Electron Microscope (STEM), operating at 80, 120 and 200 kV. It has a probe aberration-corrector, which improves imaging spatial resolution to less than 1Å. The energy resolution for electron energy loss spectroscopy (EELS) can be as small as 0.35 eV, due to its cold field emission electron gun (FEG) and the presence of a high-resolution parallel EELS detector (Gatan Enfina-ER). This instrument is ideal for probing structural and electronic properties of materials at the Angstrom level, allowing on to study the physical, chemical and electronic structure of oxide interfaces, catalysts and other functional nanomaterials. Notably, this Hitachi STEM has a secondary electron microscopy (SEM) detector for high resolution SEM imaging of the particles on the surface, with atomic resolution imaging have been demonstrated in the SEM imaging mode.
(1) H. Inada, L. Wu, J. Wall, D. Su, and Y. Zhu, J. Electron Microscopy, 58 (2009) 111
(2) Y. Zhu, H. Inada, K. Nakamura, and J. Wall, Nature Materials, 8 (2009) 808
High-angle annular dark field imaging: (a) and (b) High
angle annular dark field (HAADF) images on SrTiO3/Si interface. (c) The
structure model from a b initio calculation confirmed the atomic structure
at the interface showing in (a) and (b).
EELS at high spatial resolution: EELS is a powerful technique to probe the local compositional and electronic information. Here is an example of EELS-2D mapping on Li-battery electrode materials as how Li and Fe elements distributed at nanometer scale.
SEM Imaging. The recent achievement of 0.1nm in atomic imaging using the Hitachi HD2700C STEM suggests that SE imaging can now achieve comparable spatial resolution to the STEM mode but with complementary capabilities. For instance, as shown below, simultaneous acquisition of the SE image using secondary electrons (bottom) and the ADF-STEM image using transmitted electrons (top) of uranium oxide nanocrystals and uranium individual atoms (filtered with unsharp mask in real space) on a 2-nm carbon support.