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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.

Spontaneous generation of charged atoms or clusters was investigated during thermal evaporation of silver. For this, the effect of the applied electric bias on the film growth rate was examined during evaporation of silver at 1373 K in a tungsten basket. Film growth rates on three silicon substrates biased + 300, 0 and –300 V with respect to the chamber were 300, 420 and 960 nm per hour, respectively. The number density of generated positively-charged atoms or clusters could be measured by the electric current on the Faraday cup in the chamber. From the temperature dependence of the positive current, the activation energy for charging was determined to be ~ 2.2 eV. This value could be best explained by the surface ionization of clusters of a few atoms on the oxidized tungsten surface.

Thin film growth through nonclassical crystallization with charged nanoparticles as building blocks has been studied in chemical vapor deposition and physical vapor deposition. A similar mechanism might be applied to aerosol deposition (AD), with which the mechanism for the evolution of dense ceramic films at room temperature has not been clearly understood. Aerosol particles fracture into fragments of secondary nanoparticles during AD. In this work, secondary particles passing between the two parallel biased and grounded electrodes were captured by the transmission electron microscopy (TEM) grid membrane on each electrode, and it was revealed that they were mainly positively charged. Neutral secondary nanoparticles, not deflected by the electric field, produced a porous film on the silicon substrate, whereas charged secondary nanoparticles produced a dense film. The positive charge of the secondary nanoparticles appeared to enhance the plastic deformation required for the evolution of dense films during AD, which was supported by ab initio calculations.