The double-tubed coaxial line-type microwave plasma CVD (MPCVD) system was developed to obtain a stable plasma with a low and high gas pressure for fabrication of electronic devices and photonic devices. The a-Si:H nanoball films were fabricated by MPCVD system. In the deposition chamber, the Ar gas was fed to the outer discharge tube and the SiH4 gas was fed to the inner tube. The Ar gas was ionized in the cylindrical cavity region by the microwave power. The SiH4 gas flowed into the Ar plasma at the discharge tube end through the inner tube, and then the SiH4 was dissociated. After heat treatments for 72 h in air for as-deposited a-Si:H nanoball films, SiO2 nanoballs included Si nanocrystal characterized from XPS spectrum of the silicon 2p region. Also, from SEM and AFM observations of the oxidized surface of a-Si:H nanoball films, the size of a-Si:H nanoball was about 20-30 nm in diameter.
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