Generation of diamond nuclei has been realized on a silicon mirror surface in plasma chemical vapor deposition. Prior to the normal diamond growth process, a predeposition process of several minutes duration was introduced in which a high methane fraction in the feed gas was used and in which a negative bias voltage was applied to the substrate. This resulted in an enormous enhancement of the generation of diamond nuclei. For the onset of diamond nucleation the minimum voltage was −70 V and the minimum methane fraction in the methane-hydrogen feed gas was 5%. Density of a diamond nuclei as high as 1010/cm2 was attained with this method.

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Nanocrystalline silicon (nc-Si) has been fabricated by a very-high-frequency plasma cell attached to an ultra-high-vacuum chamber using SiH4 gas. Nanocrystalline Si is formed in the gas phase of the plasma cell and is extracted out of plasma cell through the orifice to the ultra-high-vacuum chamber. The shape of nc-Si is spherical or octahedral with the diameter of 3–30nm. Giant Si particles about 100nm in diameter are also formed at the lower cell pressure condition. A 1000keV transmission electron microscopy measurement has revealed that the core region of giant Si particle with the diameter about 30nm was crystalline and the shell region is amorphous. We have demonstrated that the spread of particle size can be decreased using pulsed gas supply of H2 into SiH4 plasma.

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