LaF3 | Optical characterization of thin films

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LaF3(Lanthanum Fluoride) thin films usually take a crystalline form. The substrate temperature and deposition rate strongly influence the optical properties of the deposited film, such as the refractive index, optical loss, spectral shift, and film stress.

Despite the considerable body of research on the use of oxide and fluoride materials for UV coatings, only a few fluoride materials can be used for coatings in the deep-ultraviolet (DUV) and the vacuum ultra violet (VUV) regions, especially when high indexes are required, due to the insufficient bandgap energy of such materials. However, LaF3 is one material that has the potential for use in the DUV and VUV regions, with a transmittance range from 130 nm to 10 μm. Note that the laser-induced damage threshold of LaF3, as tested using an ArF laser (193 nm), is relatively high compared with that of other materials for this use.