Electronic structure and optical properties of {alpha} and {beta} phases of silicon nitride, silicon oxynitride, and with comparison to silicon dioxide

Journal Article · Thu Jun 15 04:00:00 EDT 1995 · Physical Review, B: Condensed Matter

DOI:https://doi.org/10.1103/PhysRevB.51.17379· OSTI ID:74034

Xu, Y; Ching, W Y ^[1]

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1. Department of Physics, University of Missouri, Kansas City, Missouri 64110 (United States)

Effective charge calculation suggests the ionic formulas of the four crystals to be {alpha}-(Si{sup +2.52}){sub 3}(N{sup {minus}1.89}){sub 4}, {beta}-(Si{sup +2.50}){sub 3}(N{sup {minus}1.87}){sub 4}, {alpha}-(Si{sup +2.60})(O{sup {minus}1.30}){sub 2}, and (Si{sup +2.54}){sub 2}(N{sup {minus}1.90}){sub 2}(O{sup {minus}1.25}). The calculated optical properties of the four crystals show similar features in the gross absorption spectra but with differences in the peak positions. It is shown that all four crystals have intrinsic absorption tails, and those of Si{sub 2}N{sub 2}O and {alpha}-SiO{sub 2} are larger than those of {alpha}-Si{sub 3}N{sub 4} and {beta}-Si{sub 3}N{sub 4}. This is explained by the nature of the wave function at the conduction-band minimum. The difference in the intrinsic band gap and the extrapolated optical gap is pointed out. Comparison with experimental data on amorphous Si{sub 3}N{sub 4} shows good agreement with the optical conductivity of the crystalline phases. It is also shown that Si{sub 2}N{sub 2}O and {alpha}-SiO{sub 2} crystals have negligible optical anisotropy, while for {alpha}-Si{sub 3}N{sub 4} and {beta}-Si{sub 3}N{sub 4} the in-plane component of the dielectric function in the long-wavelength limit is smaller than the corresponding component parallel to the {ital c} axis. The calculated refractive indices are in good agreement with the limited data available.

• Research Organization: University of Missouri
• DOE Contract Number: FG02-84ER45170
• OSTI ID: 74034
• Journal Information: Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 24 Vol. 51; ISSN 0163-1829; ISSN PRBMDO
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ABSORPTION SPECTRA
BAND THEORY
DIELECTRIC TENSOR
ELECTRONIC STRUCTURE
ENERGY-LEVEL DENSITY
OPTICAL PROPERTIES
REFRACTIVE INDEX
SILICON NITRIDES
SILICON OXIDES
VALENCE