Computer experiments for coherent convergent-beam electron diffraction

Abstract

Considerable effort has been expended to use convergent beam electron diffraction (CBED) from small specimen areas with an incoherent thermionic source. Here space group classification and even three dimensional analysis have proven to be possible by observing the diffraction disks and the fine detail seen within these disks. The use of a coherent convergent beam has been attempted for a field emission STEM type instrument and a number of novel interference effects have recently been observed in both crystalline and amorphous materials. Preliminary CBED computer calculations were performed for a dislocation in Si3 however no structural detail was observed in the diffraction disks because the computation only considered a 30Å thick crystal. Computations covering a wide range of materials, specimen thickness values and STEM type probe conditions has been obtained by the present author. In these papers only results for zone axis patterns and 100kV electrons were given. It is now the intent to present some new results at high voltages (200kV) and for non-symmetric crystal orientations and with larger reciprocal space sampling distributions