Structure, optical absorption and photoluminescence (PL) properties of SiOx films subjected to thermal annealing at 750–1100 °C are investigated. Si crystallites with a few nanometers in size are observed in the SiO1.3 and SiO1.65 films annealed at 1100 °C. Threshold energies in optical absorption of the Si nanocrystallites are higher than that for bulk Si, suggesting a contribution from quantum confinement effects. The PL spectrum shows a remarkable increase in intensity after annealing at temperatures above 1000 °C. This PL behavior is closely related to the formation of Si nanocrystallites by the annealing. The PL peak energy of the annealed films shifts to higher energy with decreasing crystallite size but does not follow the blueshift for the absorption threshold energy. These results suggest that a localized state contributes to the PL mechanism. The SiO1.8 film annealed at 1100 °C, which contains no Si crystallites, exhibits an intense PL similar to the annealed SiO1.3 and SiO1.65 films. It is implied that noncrystalline Si nanoparticles are formed in the SiO1.8 film under high-temperature annealing.

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Polycrystalline and amorphous Si-C films were prepared by rf glow-discharge decomposition of silane-methane mixtures at 700 °C. We have demonstrated that polycrystalline SiC films with large grains grow under heavy hydrogen dilution. The bonding properties as a function of film composition and hydrogen dilution were characterized by means of x-ray diffraction and x-ray photoelectron spectroscopy. Crystallization takes place at around C content x=0.5 in Si1−xCx, accompanying some segregation of carbon atoms in grain boundaries, as a result of a preference for heteronuclear bonds. It was shown that C-C(C3−nSin) (n=0–3) bonds appear in the carbidic phase of C-rich films, leading to occurrence of compressive strain in the crystalline SiC grains. In addition, effects of hydrogen dilution were discussed in correlation with the strain.

Amorphous SiNx:H films were prepared by rf glow discharge of SiH4-NH3 mixtures at 300 °C, and the optical properties and the density Ns of Si dangling bonds obtained from electron spin resonance were investigated as a function of the N content x. The slope E0 in the Urbach form of the absorption coefficient and Ns, respectively, have a maximum at x=1.2 and 0.7. The dependence of E0 on x was examined on the basis of the random-bonding model including H atoms, and the dependence of Ns was connected with the optical gap and E0, according to the weak-bond dangling-bond conversion model.