Alkaline earth and rare-earth fluoride thin films were prepared on silica glass substrates by a sol-gel process using trifluoroacetic acid (TFA) as a fluorine source. Homogeneous solutions were obtained by stirring a mixture of alkaline earth or rare-earth metal acetates, TFA and H2O, dissolved in isopropanol. The solutions were spin-coated and heated at 300–800 °C. The fluoride thin films were obtained by heat treatment around 400 °C in air. The crystallization behavior, the surface morphology, and the optical properties of the films depended on the heating temperature as well as the chemical species of the metal ions.
Low-pressure chemical vapor deposition of silicon-germanium ͑Si 1−x Ge x ͒ and its SPC below 400°C are investigated. The effects of precursor ratio ͓SiH 4 /SiH 2 Cl 2 ͑DCS͒:GeH 4 ͔, pressure, and temperature are examined with the goals of film composition tunability and high deposition rates. SiH 4 is found to be a better source gas than DCS because the decomposition rate of SiH 4 is faster than that of DCS during the deposition process. In the SiH 4 :GeH 4 system, the binary deposition mechanism is well explained by the "enhancement" model. The deposition temperature and chamber pressure affect the conversion factor, enabling independent tuning of the film composition and deposition rate. Amorphous Si 0.7 Ge 0.3 and Si 0.5 Ge 0.5 films are obtained at 350 and 400°C by adjusting the deposition conditions while keeping the deposition rates high. Compositional effects of the SiGe films on the SPC are also investigated.
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