Live X-Ray Topography and Crystal Growth of Silicon

Dynamic observation of crystal imperfections has been made by live topography to image diffraction topographs instantaneously, using an intense X-ray source and a video camera. With the aid of synchrotron radiation, a resolution of 6 µm was achieved using an X-ray “Saticon” camera tube having an amorphous Se–As photoconductive layer. The property of the layer made avalanche amplification possible, enabling live topography using a conventional X-ray tube. Usefulness of live topography is demonstrated by in-situ observation of crystal-melt interfaces: Dislocations exist stably at equilibrium but become unstable with deviation from equilibrium leading to a dislocation-free state. This result is explained as the reverse of spiral growth. A formation mechanism of swirl microdefects is proposed on the basis of experimental results which indicate that only vacancies are intrinsic defects in silicon.