Preparation of Diamond Nanocrystallites in Powder by Using a Coaxial Arc Plasma Gun

ABSTRACTWe suggest a new method for fabricating diamond nanoclusters by employing a coaxial arc plasma gun. Diamond powder comprised of diamond nanoclusters and amorphous carbon was fabricated in vacuum and a hydrogen atmosphere, and the diamond crystallite sizes were estimated to be 1.8, 2.3, and 2.3 nm for the powders prepared at hydrogen pressures of 0, 53.3, and 159.6 Pa respectively, from the X-ray diffraction peaks. The hydrogen ambient gas is not necessarily required for the diamond nanoclusters formation. We consider that this method enables us to form diamond nanoclusters in nucleation owing to a supersaturated condition at a facing plate located in front of an arc plasma gun.

On the role of penetration twins in the morphological development of vapor-grown diamond films

Polycrystalline diamond films may be produced by chemical vapor deposition (CVD) with morphologies ranging from multimicron crystallites with well-defined facets and texture to nanocrystalline “cauliflower” nodules. While previous efforts to connect diamond film “quality” to growth conditions focus on competitive growth of non-diamond phases, we propose that twinning is a major controlling factor. We use geometric arguments to define the conditions under which a given twin can outgrow and bury the “parent” face on which it originated. We then show how the full spectrum of diamond crystallite shapes and film morphologies can be explained in terms of penetration twins without reference to the actual mechanistics of diamond growth.