(convergent beam) electron diffraction / precession electron diffraction
Electron diffraction is frequently used in material science applications, as information on crystal structure, composition and orientation can be gained with this method. We use electron diffraction in combination with dark field imaging to allocate different crystalline phases in the sample as well as to quantitatively determine the composition of mixed III/V semiconductors.
In contrast to plane wave illumination in convergent beam diffraction a convergent electron probe is used to gain information on a sample's structure. This technique can e. g. be used to determine the absolute polarity of III/V semiconductors or to address defects, strain and even point/space groups of materials. We use convergent beam electron diffraction to investigate the polarity of III/V as well as II/VI semiconductors and to determine the strain state of our materials. The diffractograms are theoretically described using a Bloch-wave algorithm.
In precession electron diffraction a hollow-cone illumination geometry of the sample is used to achieve a diffraction pattern, which is nearly free of dynamic effects. In coorperation with the TEM-group at HU Berlin we study organic samples as well as nanoclusters using this technique.