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Thin film nanocrystalline porous silicon layers have been fabricated from amorphous silicon films using dc plasma hydrogenation and subsequent annealing at temperatures about 450 °C on silicon substrates. Plasma power densities about 5.5 W/cm2 were found to be suitable for etching of the silicon film and the creation of nanoporous layers. The nanoporous structures show visible luminescence at room temperature as confirmed by photoluminescence spectroscopy. The effects of plasma power and annealing temperature on the grain size and luminescence properties of these layers have been investigated by scanning electron microscopy, transmission electron microscopy, photoluminescence, and cathodoluminescence. It was observed that by lowering the temperature during the hydrogenation step, the diameter of the grains increased, whereas lowering the plasma power density caused the distribution of the porous surface structures to become less widely distributed and the formation of more packed structures. In addition, infrared spectroscopy has been used to investigate the origin of the light emitting behavior. [ABSTRACT FROM AUTHOR]

The effects of plasma-enhanced hydrogenation on the crystallization of pure, electron-beam evaporated amorphous silicon (a-Si) at temperatures as low as 300 °C were investigated. Successive steps of hydrogenation in the plasma-enhanced chemical vapor deposition chamber, and in situ annealing in a N2 ambient environment were applied to the a-Si samples over a range of low temperatures and plasma powers. At specific plasma-power densities, nanocrystalline silicon layers with an average grain size of less than 10 nm were formed where their size, distribution, and porosity could be varied by altering the plasma power and hydrogenation temperature. The surface morphology and the nanocrystalline quality of the samples were characterized using scanning electron microscopy, dark-field transmission electron microscopy, and electron diffraction. In addition, by plasma-enhanced oxidation at a temperature of 250 °C, a thin layer of oxide was grown and its physical, structural, and electrical characteristics were investigated. [ABSTRACT FROM AUTHOR]