Diamond nucleation enhancement by direct low-energy ion-beam deposition

Direct ion beam deposition was successfully applied for the nucleation of nanodiamond crystallites on mirror-polished Si(001) substrates. Low-energy (80-200 eV) argon, hydrocarbon, and hydrogen ions from a Kaufman ion source were used. An amorphous carbon film was deposited on the substrate after ion bombardment. The films were characterized by high-resolution transmission electron microscopy, selected area electron diffraction, secondary electron microscopy, and micro-Raman spectroscopy. At ion doses above 1 x 10(18) cm(-2), nanocrystalline diamond particles of 50-100 Angstrom in diameter were formed in a matrix of amorphous carbon. These diamond nanocrystals served as nucleation centers for subsequent diamond growth by conventional hot filament chemical vapor deposition. The nucleation density depended strongly on the ion dosage, and a nucleation density of 3 x 10(9) cm(-2) could be achieved under optimized conditions. These results were found very helpful for the evaluation of the mechanism of ion-bombardment-induced nucleation of diamond.