Simulation of dislocations imaged by moiré fringe contrast

Transmission electron microscope (TEM) images of dislocations as produced via moiré fringe contrast are simulated using many-beam diffraction theory. The effect of edge dislocations on both parallel and rotational moiré fringe patterns is considered. For the parallel moiré fringe pattern, images of dislocations both perpendicular to the film plane and those inclined to the film plane are produced. The effect of an inclined dislocation is shown to cause a distortion of the dislocation image. Finally, a comparison between predicted and experimentally observed images is made, with the results indicating that threading dislocations in the FeAl/GaAs system have line directions nearly perpendicular to the (001)FeAl/GaAs film plane.