Effects of secondary pretreatments of substrate on the nucleation of diamond film

The effects of secondary pretreatments on diamond nucleation were investigated for the Si substrates pretreated by the diamond abrasion. When the substrate was just abraded with diamond powder, the nucleation density of diamond was 7 × 10⁸/cm². However, the nucleation density was found to be greatly decreased by various secondary pretreatments except by one wet chemical etching method. The nucleation density was reduced to 3 × 10⁷/cm² by the chemical etching (I), to 7 × 10⁶/cm² by the H₂ plasma etching, and to ∼10⁴/cm² by the Ar sputtering, or O₂ plasma etching. It was very slightly reduced to 3 × 10⁸/cm² by the chemical etching (II). The effects of secondary pretreatments in reducing the nucleation density were found to be very closely related to the removal of diamond seeds rather than topographic sites or structural defects. Therefore, diamond seeds generated by the diamond abrasion are considered as the main nucleation sites of diamond.