High-resolution X-ray topography

X-ray double-crystal topography is, together with section topography, the most deformation-sensitive method. Its advantages and problems are discussed especially in view of the widely spread Lang topography. There are advantages regarding sensitivity, exposure time and the simplicity of contrast evaluation. The disadvantage of its sensitivity to sample warping can be overcome to some extent by a special double-crystal technique with an adaptable bending of the collimator crystal compensating for a homogeneous sample curvature. In contrast to other techniques, double-crystal topography preserves its high-deformation sensitivity also in reflection geometry. That is advantageous if near-surface defects and deformations are investigated as shown by several examples.