Pseudo moire dislocations appearing in x-ray diffraction topography

In recent x-ray moire topographic experiments a dislocationlike discontinuity of moire fringes has been found despite the fact that specimens (Si bicrystal) were dislocation free. This discontinuity, although similar in appearance to the fringe discontinuity known as moire dislocation, should be essentially distinguished from it. Preliminary considerations suggest that the outbreak of such pseudo-moire dislocations is related not only to the wave-field phase due to the moire effect, but to the phase of extinction fringes. Pseudo-moire dislocations commonly occur in plane-wave x-ray moire topography of slightly strained specimens. (C) 1996 American Institute of Physics.