Three-dimensional imaging of crystal defects by 'topo-tomography'

A new technique, 'topo-tomography', suitable for the characterization of th e three-dimensional defect structure in bulk crystals, is proposed. The tec hnique consists of the combination of diffraction topography and microtomog raphy. It is applicable to high-quality single crystals, provided that the 'direct image' is the dominant contrast mechanism. In this case, crystal de fects give rise to locally enhanced intensity compared with the perfect-cry stal matrix. The additional intensities sum along the diffracted-beam direc tion and yield projections of the local Bragg reflectivity. Like in the cas e of absorption tomography, the three-dimensional distribution of this refl ectivity can be reconstructed from a large number of projections. The first experimental results of this technique, applied to a synthetic diamond cry stal, are presented.