Comparison of Weak-Beam and Bright Field Conditions

The two pictures below show the extremes in resolution.
On the left hand side is a weak beam image of a dislocation network in a small angle grain boundary in Si; it has optimum resolution. The dislocation end at a SiO2 precipitate which shows faint fringes due to Moirée effects (the Si precipitate is sandwiched between Si crystals which are slightly misoriented).
On the right hand side is the same area imaged with (rather dynamical) bright field conditions. The dislocation lines are very broad and their images interfere with each other; it would be difficult to interpret this picture.
Comparison weak-beam and bright field

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go to 6.3.2 Examples and Case Studies for Dislocations

© H. Föll (Defects - Script)