NUCLEATION ENHANCEMENT BEHAVIOR OF DIAMOND ON SI SUBSTRATE ACCORDING TO SURFACE-TREATMENT MATERIALS

The dependence of diamond nucleation on pretreatment materials was inv estigated. Diamond, cubic boron nitride (c-BN), silicon carbide (SiC) and alumina (Al2O3) powders with an average particle size of 3 mu m we re used for surface treatment. Si substrates are vibrated ultrasonical ly in a powder-acetone mixture and then cleaned in acetone. Diamond wa s deposited on the treated Si substrate by a tungsten filament: CVD (H FCVD) method under the following conditions: 40 mbar of pressure, 1% o f methane in hydrogen, 800 degrees C substrate temperature. The nuclea tion density was decreased until saturated as the substrate cleaning t ime increased regardless of the substrate treatment material. However, the saturated nucleation density decreased in the order of diamond, c -BN, SiC and finally Al2O3. The residue of the treatment material on S i surface was detected after cleaning for a long period of time. The m easured density of residue decreased in the same order to that of the diamond nucleation density. Furthermore, the ratio of the density of n ucleated diamond to that of the residue decreased in the order of diam ond, c-BN, SIC and lastly Al2O3. The larger the lattice difference bet ween the residue material and diamond, the smaller the nucleation dens ity. This result suggests that the residue of the treatment powder pla ys a significant role as a site for the diamond nucleation. The possib ility of surface shape and defects as a nucleation site is also discus sed. (C) 1997 Elsevier Science S.A.