The selective etching of hydrogenated amorphous silicon (a-Si:H) with respect to crystalline Si (c-Si) by hydrogen plasma is investigated. We have revealed that a-Si:H is etched ten times faster than c-Si. With lower etching temperature, etching selectivity and etching rate of a-Si:H and c-Si increase. Under the high-pressure condition, the etch rate becomes low because the bright region of a very-high-frequency plasma moves away from the grounded electrode. The etching rate of a-Si:H is not sensitive to the structure of the a-Si:H deposited at 70–300° C. The surface morphologies of etched a-Si:H and c-Si are rougher for higher etching temperature. The mechanism of selectivity in etching is discussed.

This paper presents results on the fabrication of single electron tunneling devices using silicon nanocrystals. We prepare silicon nanocrystals of uniform particle size by very-high-frequency plasma processing and deposit them on a poly-silicon electrode structure having a very small inter-electrode separation of 26–70 nm. Current-voltage (I–V) characteristics show Coulomb blockade and Coulomb staircase at 77 K. For very narrow electrode separation, Coulomb staircase appears in I-V characteristics even at room temperature.

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Si-based coatings were formed on iron surfaces by low pressure chemical vapor deposition of pure SiH4 and He-diluted SiH4 under the following conditions: temperature of 350 to 850°C, gas flow rate of 0.1 to 100 sccm, gas composition of pure or He-diluted SiH4, pressure of 0.01 to 600 Torr and deposition time of 2 to 20 min. Coatings are essentially overlay type, with more than 30 at.% Si, for temperatures between 350 to 650°C regardless of other conditions. When the temperature exceeds 650°C, low gas flow rates (<10 sccm) produce diffusion type coatings with 26-29 at.% Si, whereas high gas flow rates form overlay coatings with underlying diffusion layers containing 2-5 at.% Si. Adjustment of conditions, mainly temperature and gas flow rates, allows the control of overlay or diffusion characteristics and composition gradient of coatings.