Soft ion impact for surface activation during diamond chemical-vapor deposition on diamond and silicon

Extremely low-energy ions with a mean kinetic energy of around 2 eV have been used for surface activation during diamond chemical-vapor deposition at a pressure of 20 mTorr in an inductively coupled plasma. A qualitative model based on a current balance between a positively biased substrate and a surrounding wall was given to describe the variation of ion energy and flux onto the substrate. The deposits with polycrystalline morphologies were obtained on the biased diamond(100) and Si(100) substrates by varying the ion flux. The ion-enhanced surface migration of hydrocarbon adatoms was demonstrated by the ion flux dependent morphologies of diamond films grown on diamond. A high ion flux resulted in large interisland distance and island size, a low island density, and a low fraction of grain boundary. In contrast, the concurrently induced disadvantage like surface defects and etch pits was shown by the ion flux dependent morphologies of nanocrystalline diamonds grown on Si. A high ion flux resulted in nonfacetted crystallites and a high frequency of secondary nucleation. Comprehensive discussion on the role of low-energy ions in the growth kinetics suggests that soft ion impact is promising for modifying thermally dominated behaviors of adsorbed radicals and exploring simple processes.