Effect of substrate materials in the low-pressure synthesis of diamond: approach by theory of charged clusters

The relationship between substrate materials and the deposition of diamond or graphitic soot was studied in the low-pressure synthesis of diamond. Electrocatalytic metals such as Fe, Ni, Rh, Pd, Pt, and Ir result in soot deposition while insulating materials such as Al2O3and SiO2result in diamond deposition. There exists a strong correlation between the electrocatalytic substrate materials and soot deposition. The substrate dependence of the deposition behavior is approached by the theory of charged clusters. The substrate dependence is suggested to be related to the charge-transfer rate at the substrate surface for charged clusters, which had formed in the gas phase. The evolution of soot and diamond is explained in terms of the floccula-tion and deflocculation behavior of colloid particles, respectively.