Plasma deposition and characterization of photoluminescent fluorinated nanocrystalline silicon films

Fluorinated nanocrystalline silicon films, nc-Si:H,F, have been deposited from SiF4-SiH4-H2 mixtures by means of the plasma enhanced chemical vapor deposition technique. The presence of fluorine atoms, which are effective etchant species, promotes selective etching giving nanocrystalline films. These materials, with grain size of 100-200 Å, show a room temperature photoluminescence centered at 1.62 eV. Also, the widening of the optical energy gap (Eg=2.12 eV) is mainly due to the presence of nanocrystals rather than to the H content of 4.5 at. %.