Defects in Quartz Studied By Transmission Electron Microscopy and X-Ray Diffraction Topography

Of the methods used in the study of defects in crystals employing diffraction contrast, transmission electron microscopy is preeminent on account of its high resolution..., speed, magnifying power (up to 10-6 times), and the high defect density (e.g. 10-18 dislocations cm-2 or more) it can handle. The method of X-ray topography, on the other hand, is a slow method to produce an unmagnified image of the specimen and at its best it has a practical resolution limit of about one micron. It follows that X-ray topography cannot compete at all with electron microscopy where resolution, magnification, and speed is concerned. However, X-ray topography is quite informative with undeformed or very lightly deformed good quality crystals having a low defect density (e.g. 10-6 dislocations cm -2 or less ) , because in such fairly perfect crystals the volume sampled in an electron micrograph is too small to give an estimate of the defects.