Vacuum ultraviolet loss in magnesium fluoride films

The optical constants of evaporated MgF//2 films were determined over the 1050 to 1600-A wavelength range from measured transmittance and near-normal incidence reflectance measurements. The complex refractive index was studied as a function of film deposition conditions and correlated with microstructural examinations by transmission electron microscopy. Absorption by the low energy tail of an exciton band and scattering from inhomogeneities were found to account for the film's loss in this wavelength range. Both of these factors were determined largely by substrate temperature during the film deposition.