SYNTHESIS AND GROWTH-MECHANISM OF FLATTENED DIAMOND CRYSTALS BY CHEMICAL-VAPOR-DEPOSITION

Flattened diamond crystals were synthesized under high oxygen gas conc entration and low substrate temperature conditions using the oxy-acety lene dame method. The flattened morphology appeared because preferenti al growth occurred along side faces owing to the presence of twin re-e ntrant corners. This ''re-entrant corner effect'' can be expected only under the condition of a low two-dimensional nucleation rate. Therefo re, the flattened diamond crystals are synthesized only under the cond ition of a high oxygen gas concentration because when the oxygen to ca rbon ratio is increased, the two-dimensional nucleation rate is suppre ssed by the decrease in supersaturation of the source gas. Also, the t win re-entrant corners are formed as hexagonal diamond nuclei moving o n the substrate coalesce together.