Nb2O5 | Optical characterization of thin films

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Nb2O5(Niobium pentoxide) is one of the most popular high-index materials for UV-to-VIS applications, with a refractive index of 2.33 at 550 nm and a transmittance range from below 320 nm to 8 μm. It is a common alternative to TiO2, which absorbs wavelengths under 400 nm. Nb2O5 thin films are known to have low film stress and good stability. With IAD, spectral shifts are less likely to occur with this material than with TiO2, and the deposition conditions are much more easily controlled. However, too much irradiation at high ion energies can sometimes crack the Nb2O5 thin film. Also, the use of IAD reverses the film stress direction.

For continuous production, the granule type is very popular, as it can be used to refill the crucible; however, too much refilling will result in increased film absorption. This occurs because Nb2O5 tends to dissociate with oxygen more easily than other oxides, and inside the crucible, each refilled layer tends to have different amounts of oxygen.