Characterization of photoluminescence of a-Si: H nanoball films fabricated by microwave plasma CVD

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.