Cold-cathode fluorescent lamps (CCFLs) are being used for LCD backlighting and is currently the dominant technology for LCD backlighting. However, recent attention has been given to LEDs as light sources for LCD backlighting because of their (i) long life, (ii) low-voltage operation, (iii) fast response time, and (iv) wide color gamut. This review article commences with the basics of LEDs as light sources and their limitations, followed by various backlight structures employing LEDs in cell phones, notebook computers, and LCD TVs. The description of the improvement in image quality on an LCD screen, stemming from the characteristics of LEDs, is also given. In conclusion, the possible rapid growth of LED backlights is outlined, thus gradually ending the domination of CCFL backlights.

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Silicon dioxide films grown by photochemical vapor deposition at different deposition rates are investigated by ellipsometry and Fourier transform infrared measurements. Disagreement in the variation of refractive index with chamber pressure between thin and thick films is interpreted in terms of a deposition rate dependent buildup of internal stress in the film. Direct measurements of curvature show the presence of compressive stress in thick SiO2 films grown at chamber pressures ≳600 mTorr. Infrared transmission measurements also indicate a change in the structural characteristics of films (probably induced by stress), with increasing deposition rate. Molecular model calculations show a decrease in the Si—O—Si bond angle as the growth pressure increases. Ion implantation seems to release the stress in these films as evidenced by the shift observed in the stretching mode frequency. The relative concentrations of H2O, SiOH, and SiH groups in these films and the effect of annealing on the strength of these modes are also discussed. Reflection infrared measurements at 60° incidence reveal a disorder induced longitudinal-transverse optic pair at around 1200 cm−1.

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