electron microscopy
 

HOMEMETHODSINTERACTIONSDOWNLOADSCONTACT
RESEARCH: RECENT HIGHLIGHTSEXAMPLES


 

Comparison between HRTEM and HAADF-STEM (Z contrast)

 

basics
interference of coherently scattered electron waves
incoherent scattering
recording method / time
parallel / 0.5 – 2 s

serial / 5-20 s
(more problems with sample stability and drift)

cathode
LaB6 or FEG
FEG

point resolution
of a Tecnai F30
of a Cs-corrected
microscope

ca. 2 Å

< 0.5 Å

ca. 2 Å

< 0.5 Å

obtainable information
atomic positions (and elemental distribution)
atomic positions and elemental distribution
image interpretation
comparison with simulations; at Scherzer defocus: atom columns dark
direct: atom columns always bright; intensity ~Z2

Example: WO3 segregations in a niobium tungsten oxide

 
F30
HRTEM
HAADF-STEM


The positions of the metal atoms are recognizable in the HRTEM image recorded close to Scherzer defocus as dark dots while they always appear with bright contrast in the HAADF-STEM (Z contrast) image. The different brightnesses of dots in the Z contrast image indicate varying occupancies of the corresponding metal position by Nb and W (see: Krumeich, Nesper, J. Solid State Chem. 179 (2006) 1857-1863 DOI).

A useful introduction into theory and practice of TEM and STEM is given on the web site of Rodenburg.

ETH Zürich | ETH chemistry department | ETH inorganic chemistry

modified: 4 January, 2016 by F. Krumeich | © ETH Zürich and the authors