Analysis of defect structures in high purity copper single crystals using x-ray topographic techniques

Citation

Hamill, Gregory P. (1978) Analysis of defect structures in high purity copper single crystals using x-ray topographic techniques. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/51fg-6x90. https://resolver.caltech.edu/CaltechETD:etd-09162002-105352

Abstract

Copper single crystals were grown in a modified Czochralski system. The "grown-in" dislocations and those introduced through selective scratching of the polished (111) surfaces were observed using Berg-Barrett X-ray topography and Borrmann transmission topographic methods.

Several aspects of the dislocation images may be understood on the basis of pure dynamical or kinematical theories of X-ray diffraction. Some observations, however, support the theory that both dynamical and kinematic effects must be considered to properly describe the experimental results.

Stereo depth measurements of the dislocation images were taken under four sets of X-ray geometries. The minimum range of depths observed, approximately 1.0 to 2.0?m from the surface, was obtained for both methods of Berg-Barrett stereo topography. The Borrmann transmission topographs provided an image depth range of approximately 3.0 ?m from the exit surface to 270 ?m from the exit surface. This latter value is equivalent to the crystal thickness, to the accuracy of the present data. Comparison of reflection (Berg-Barrett) and transmission (Borrmann) topographs of the same crystal showed that no image of an individual dislocation on one topograph had a corresponding image on the second topograph.

An attempt to mark the surface of the crystal by vapor depositing gold dot "absorbers" on the surface was not completely satisfactory due to a shadowing effect in Berg-Barrett topography. The apparent epitaxial growth of the gold dots on the (111) copper surface and the corresponding strain field in the crystal around the dots provided a reference surface for transmission topography, although the true surface was marked only in the asymmetric stereo topographs.

Computer simulation using finite element analysis is proposed to solve the problems of X-ray image formation.

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