Ion channeling in natural diamond. Minimum yields

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Abstract
Reasons for the desirability of obtaining a comprehensive set of good ion-channeling measurements for diamond are outlined. Good-quality crystals must first be selected from the available natural specimens, and experiments are reported which show that the best selection criterion is the channeled minimum yield itself. Methods of improving the crystal quality and precautions to be taken to ensure accurate results are considered. Minimum-yield measurements were made for a variety of axes, planes, ions, energies, and diamond temperatures. The results agree quite well with theoretical predictions. The very small value of the thermal vibration amplitude in diamond even at moderately elevated temperatures (relative to the Thomas-Fermi screening distance) provides a good test of theory and enables the values of certain parameters to be determined with greater accuracy than is usually possible. The inadequacy of a simple geometrical model for the origin of the minimum yield is emphasized by its predominant dependence on thermal vibrations even in this very "cold" crystal. These experiments also shed some light on the nature of the free diamond surface.