images of Pt particles in SiO2 nanotubes
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.
image of Au/Pt particles on Silica
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 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).
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
HAADF-STEM image of Nb4W13O47 oxidized
at 1000°C. Projection along the short axis.