electron microscopy
 

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Examples of STEM images

STEM images of Pt particles in SiO2 nanotubes


BF, ADF, and HAADF STEM images of Pt-filled SiO2 nanotubes

In the BF-STEM image, the contrast is similar to that in BF-TEM images: Pt particles appear with dark contrast since they are crystalline and the heaviest scatterers in this system. In the ADF-STEM image, the Pt particles appear with bright contrast because of diffraction and incoherent scattering (cf., DF-TEM images). In the HAADF-STEM image, only the incoherently scattered electrons contribute to the image, which nonetheless appears to be very similar to the ADF-image.

 

HAADF-STEM image of Au/Pt particles on Silica
In the high-angle annular dark field (Z contrast) image, the metal particles, which have high atomic numbers Z compared to the SiO2 matrix, are imaged as bright dots. Thus, this method is a valuable tool to investigate catalysts and to determine the sizes of metal particles and the corresponding size distribution.
Structural imaging by HAADF-STEM

This HAADF-STEM image shows WO3 segregations in a matrix of a TTB-type Nb-W oxide. The positions of the metal atom columns appear with bright contrast (c.f., HRTEM image of Nb4W13O47).

Oxidation Products of the Niobium Tungsten Oxide Nb4W13O47: A High-Resolution Scanning Transmission Electron Microscopy Study
F. Krumeich and R. Nesper
J. Solid State Chem. 179 (2006) 1857-1863 DOI


Fourier-filtered HAADF-STEM image of Nb4W13O47 oxidized at 1000°C. Projection along the short axis.


STEM
| Detectors | Aberration-corrected STEM
Comparison with HRTEM

 

ETH Zürich | ETH chemistry department | ETH inorganic chemistry | Nesper group | EMEZ

modified: 18 December, 2014 by F. Krumeich | © ETH Zürich and the authors