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Various fluorides are materials in nature that extend their transparency range to the shortest wavelengths in the far ultraviolet (FUV, 100nm<¿<200 nm). These are relevant materials to prepare multilayer coatings in the FUV for demanding applications such as space instrumentation for astrophysics, solar physics and atmosphere physics, as well as free electron lasers, plasma diagnostics, synchrotron radiation, lithography, spectroscopy, etc. Multilayer design requires the optical constants of the coating materials. Multilayers optimally alternate two transparent materials with contrasting refractive indices. The optical constants of a low-index material, MgF2, and of two high-index materials, LaF3 and CeF3, have been determined in a wide spectral range and are presented here. Thin films of MgF2, LaF3, and CeF3 were deposited by boat evaporation onto substrates at 523 K. Transmittance, reflectance, and ellipsometry measurements were performed in ranges jointly covering the 30- 950-nm spectral range. This range was extended with literature data and extrapolations to obtain self-consistent optical constants using the Kramers-Kronig (KK) analysis. An iterative, double KK analysis procedure (successive reflectance-phase and k-n KK analyses) was carried out to obtain a self-consistent set of optical constants per material. With the final data sets, the experimental measurements were satisfactorily reproduced. Global self-consistency of the data sets was successfully evaluated through sum rules; additionally, local selfconsistency at each photon energy range was also evaluated through a novel sum-rule method which involves window functions. The new sets of optical constant extend the data availability mainly to the FUV and beyond, particularly for CeF3, where few data had been reported.

Self-consistent optical constants of SiO and TaO films have been obtained for their relevance in optical coatings from the near ultraviolet to the near infrared spectral ranges, where they are transparent and have a high refractive index contrast. Particular attention has been paid to wavelengths close to and shorter than each material cutoff. The far and the extreme ultraviolet ranges are also covered here, where few (SiO) or almost no optical constant data (TaO) were available for films of these materials. This work is aimed at filling the lack of self-consistent sets of optical constants with data in a very broad spectral range, which can be widely applied in multilayer design for the everyday use of these materials in multilayer coatings. Oxide films were deposited by reactive electron-beam evaporation onto various sorts of substrates at 573 K. Transmittance, reflectance, and ellipsometry measurements were performed for each oxide in spectral intervals jointly covering from the extreme ultraviolet to the near infrared; starting with these measurements along with extrapolations, an iterative and double Kramers-Kronig analysis procedure has been followed to obtain a self-consistent set of optical constants per material. With the final data sets, we have satisfactorily reproduced the experimental measurements. Global data selfconsistency was successfully evaluated through sum rules, and local consistency at each photon energy range was also evaluated through a novel sum-rule method which involves window functions. © 2016 Optical Society of America

© 2015 Optical Society of America. The low expected absorption of Ca in the extreme ultraviolet (EUV) makes it an attractive material for multilayers and filters because most materials in nature strongly absorb the EUV. Few optical constant data had been reported for Ca. In this research, Ca films of various thicknesses were deposited on gridsupported C films and their transmittance measured in situ from the visible to the soft x-rays. The measurement range contains M2,3 and L2,3 absorption edges. Transmittance measurements were used to obtain the Ca extinction coefficient k. A minimum k of 0.017 was obtained at ∼23 eV, which makes Ca a promising low-absorption material for EUV coatings. A second spectral range of interest for its low absorption is below the Ca L3 edge at ∼343 eV. Measured k data and extrapolations were used to calculate the refractive index n using Kramers.Kronig relations. This is the first self-consistent data set on Ca covering a wide spectral range including the EUV.

The optical constants of ion-beam-sputtered B 4C films have been measured by ellipsometry in the 190-950nm range. The set of data has been extended toward both shorter and longer wavelengths with data in the literature, along with interpolations and extrapolations, in order to obtain a self-consistent set of data by means of Kramers-Krönig analysis. All data correspond to films that were deposited by sputtering on nonheated substrates, and hence they are expected to be amorphous. The B 4C bandgap was calculated as a fitting parameter of Tauc equations for indirect transitions using the present optical constants. Good global accuracy of the data was estimated through the use of various sum rules. The consistent data set includes the visible to the extreme UV (EUV); this large spectrum of characterization will enable the design of multilayer coatings that combine a relatively high reflectance in parts of the EUV with a desired performance at a secondary range, such as the visible. © 2011 Optical Society of America.

The optical constants of erbium (Er) films were obtained in the 3:25-1580 eV range from transmittance measurements performed at room temperature. Thin films of Er were deposited by evaporation in ultra high vacuum conditions and their transmittance was measured in situ. Substrates consisted of a thin C film supported on a grid. Transmittance measurements were used to obtain the extinction coefficient k of the Er films. The refractive index n of Er was calculated using the Kramers-Krönig analysis. k data were extrapolated both on the high- and low-energy parts of the spectrum by using experimental data and calculated k values available in the literature. Er, similar to other lanthanides, has a low-absorption band below the O2,3 edge onset; the smallest absorption was measured at ~22:5 eV. Therefore, Er is a promising material for filters and multilayer coatings in the energy range below the O2,3 edge, in which materials typically have an absorption stronger than at other energies. Good consistency of the data resulted from the application of f and inertial sum rules. © 2011 Optical Society of America.

The optical constants of ion-beam-sputtered SiC films have been measured by ellipsometry in the 190 to 950nm range. The set of data has been extended both toward shorter and longer wavelengths with data in the literature, along with inter- and extrapolations, in order to obtain a self-consistent set of data by means of Kramers-Krönig analysis. All data correspond to films that were deposited by sputtering on nonheated substrates, and hence they are expected to be amorphous. A bandgap of 1:9 eV for the films was fitted from the obtained optical constants. A good global accuracy of the data was estimated through the use of various sum rules. The consistent dataset includes the visible to the extreme ultraviolet (EUV); this large spectrum of characterization will enable the design of multilayer coatings that combine a high reflectance in parts of the EUV with desired performance at a secondary range, such as the visible. To our knowledge, this paper provides the first compilation of the optical constants of amorphous SiC films. © 2011 Optical Society of America.

A new type of multilayer coatings with narrowband reflection properties and peaked in the ∼50-92 nm spectral range has been developed. Multilayers are based on Yb, Al, and SiO films and they have been prepared by thermal evaporation. Efficient multilayers based on Yb and Al, with an SiO protective layer were prepared, but they developed a dendrite structure, which was attributed to the reactivity between Al and Yb. Multilayers based on Yb and Al, with both SiO protective and barrier layers, resulted in efficient reflective filters, with no observable dendrite growth. The peak reflectance of aged multilayers was of the order of ∼0.20, with bandwidths in the range of 12 to 22 nm FWHM. © 2009 Optical Society of America.

Boron films deposited by evaporation with an electron-beam were found to have a relatively high reflectance in the extreme ultraviolet with values similar to those of ion-beam-sputtered (IBS) SiC and IBS B4C . The largest reflectance was measured for an 11¿nm thick boron film. Some reflectance degradation was observed for boron films stored in a desiccator. Reflectance degradation varied from sample to sample and was found to be either similar to that of IBS SiC and IBS B4C or larger. © 2008 Optical Society of America

Experimental measurements of the angular distribution of scattering and scanning electron microscopy pictures of thin aluminum films were used to relate the total integrated scattering and the statistical parameters of the surface roughness to the film thickness. © 1993 Optical Society of America