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We report on the optical properties and local bonding configurations of both as-deposited and postannealed hydrogenated amorphous silicon nitride ͑a-SiN x :H͒ thin films grown on crystalline Si substrates with x approximately 1.2± 0.1. Ultraviolet optical reflection and infrared ͑IR͒ absorption measurements were applied to characterize the films. A method simply based on optical reflection spectra is proposed for accurate determination of the optical band gap, band tail, wavelength-dependent refractive index and extinction coefficient, as well as the film thickness, suggesting that the Tauc-Lorentz ͓G. E. Jellison, Jr. and F. A. Modine, Appl. Phys. Lett. 69, 371 ͑1996͒; 69, 2137 ͑1996͔͒ model with the inclusion of Urbach tail is the optimal one to describe the optical response of a-SiN x : H films. The yielded optical parameters can be related well to the film microstructure as revealed by the IR absorption analysis. These results have implications for future deposition controlling and device applications.

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Sibling history of diabetes was more strongly associated with diabetes risk than parental history among high-risk subjects. Subjects with a sibling or maternal history of diabetes had significantly lower insulin secretion. Sibling history is an important and independent risk factor for diabetes even among multi-risk populations. Those with a sibling history of diabetes warrant intensive care and follow-up screening.

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We report room-temperature visible photoluminescence (PL) properties of highly ordered hydrogenated nanocrystalline Si(nc-Si:H) with good electrical performance. The PL profiles can be well reproduced by the model of Islam and Kumar [J. Appl. Phys. 93, 1753 (2003)], incorporating the effects of quantum confinement and localized surface states, as well as a log-normal crystallite size distribution. Raman, PL, and electrical results consistently reveal that improvement of structural order within nc-Si:H is beneficial to enhance the PL efficiency. Owing to adequate order, strong visible PL and high electron mobility can coexist in nc-Si:H, which may provide possibilities in Si-based optoelectronics.

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