| Effect of substrate pretreatment materials on diamond nucleation density on Si substrate was investigated. The powder used for substrate pretreatment were diamond, c-BN, SiC and Al₂O₃ whose size were about Sum. The substrate was vibrated ultrasonically being immersed in powder-acetone mixture solution. The diamond was deposited on the substrate by hot filament CVD method. With the increase pf pretreatment time, the nucleation density of diamond increased and saturated at values which decreased in the order of diamond, c-BN, SiC and Al₂O₃. The density of residue of pretreatment powder was measured by AFM and compared with the nucleation density. The nucleation density of diamond varied as the same tendency with the residue density of pretreatment powder. However the ratio of diamond nuclei to the residue decreased rapidly in the order of diamond, c-BN, SiC, Al₂O₃. This was related to the similarity of lattice between the diamond and pretreatment material. As the lattice structure and size of pretreatment powder deviated from diamond, the nucleation appeared more difficult. The possible effect of surface roughness and defect near the surface on the nucleation was also discussed. |
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