OPtical constants of solids, n the index of refraction, and k the extinction coefficient, are essential for designing components for use in optical instruments, i.e., reflectors, transmitters, etc. In the UV region (4000 - 2000 Å) there are many transmitting glasses and crystals from which ellipsometers can be constructed, consequently extensive use of ellipsometry over the long wavelength part of this region can provide index of refraction values of non-absorbing media accurate to five significant figures. As the wavelength decreases, however, the ellipsometric technique becomes difficult because the components of teh measuring apparatus become absorbing. In the extreme ultraviolet (XUV) from 2000 to 2 A less precise techniques are used. Over most of this region the reflectance vs. angle of incidence (R vs. Φ) method is the mainstay. Such n,k measurements can be accurate to three significant figures, seldom more. Furthermore, the method is n,k dependent, i.e., in certain regions of the n,k plane the precision for n or k becomes less than three significant figures while the other value may be more precise; an n,k uncertainy principle. Some ellisometric instrumentation has been developed for the XUV but the spectral range is limited. Other techniques are available for limited spectral ranges; for example, measuring n from R vs. Φ curves and measuring k from transmission through thin films, measuring R at near normal incidence over extended wavelength ranges and using the Kramers-Kronig (KK) relations to obtain n,k. Non-optical techniques, such as bombardment of unbacked films with electrons to determine the location and shape of their plasmon oscillation, are useful for limited wavelength ranges.

We have produced and characterized Mo/Y multilayers designed as linear-polarizers for use near λ ~ 8 nm. By depositing these films directly onto silicon photodiodes, we are able to measure both reflectance and transmittance in the EUV using synchrotron radiation. These measurements have been used to access the accuracy of yttrium optical constants in this wavelength range. We describe our experimental results and discuss the prospects for the future development of efficient EUV polarization elements.

Near-edge x-ray absorption resonances provide information on molecular orbital structure; these resonances can be exploited in x-ray spectromicroscopy to give sub-50-nanometer resolution images with chemical state sensitivity. At the same time, radiation damage sets a limit to the resolution that can be obtained in absorption mode. Phase contrast imaging may provide another means of chemical state imaging with lower radiation dose. We describe here the use of experimentally measured near-edge absorption data to estimate near-edge phase resonances. This is accomplished by splicing the near-edge data into reference data and carrying out a numerical integration of the Kramers-Kronig relation.

The rocket Extreme ultraviolet Grating Spectrograph (EGS) instrument is flown onboard a sounding rocket as an underflight calibration for the Solar Extreme ultraviolet Experiment, or SEE, onboard the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite. The first calibration flight took place from the White Sands Missile Range in New Mexico on February 8, 2002. Both pre-flight and post-flight calibrations are performed in the extreme ultraviolet (EUV) range from 26.5 nm to 117.2 nm and the far ultraviolet (FUV) range from 120 nm to 196 nm in order to determine an accurate quantum throughput (QT) for the EGS instrument. These calibrations are performed using Beam Line 2 (BL2) at the National Institute of Standards and Technology (NIST) Synchrotron Ultraviolet Radiation Facility III (SURF-III). This QT determination has an uncertainty of about 6% for the EUV region and around 3.5% for the FUV region. Once the QT for the instrument is found from the calibrations, it is applied to the solar spectrum obtained during the flight in order to get the absolute spectral irradiance with an uncertainty of approximately 10%. This rocket spectrum is then applied to the SEE EGS to obtain absolute irradiance values for the satellite instrument and to calibrate it for changes, such as degradation, that have occurred since its own pre-flight calibrations. This calibration transfer is done by scaling the SEE EGS solar spectrum at the time of the rocket flight to the rocket spectrum to get the same irradiance values, which produces a scaling factor that can be applied to other SEE EGS measurements. The rocket EGS is planned for an annual calibration flight to track the long-term changes of SEE EGS.

The computational design of multilayer-coated diffraction gratings for the extreme ultraviolet (EUV) wavelength region and the experimental performance of the coated gratings depend on the optical constants of the layer materials. While accurate optical constants are available for many commonly used materials, the EUV optical constants can in practice differ significantly from the tabulated values. This is generally true near absorption edges, for reactive materials that may be subject to oxidation or contamination, and for the longer EUV wavelengths (>30 nm) where molecular effects can be important. Normal-incidence gratings with Mo/Si coatings operating in the 17-21 nm and 25-29 nm wavelength ranges were successfully designed and fabricated for the Extreme Ultraviolet Imaging Spectrometer (EIS) on the Solar-B mission, the first satellite instrument to carry a multilayer grating. Examples of multilayer gratings designed and fabricated for wavelengths <12 nm and >40 nm, using materials other than Mo/Si, will be given that have in many cases required the experimental determination of the optical constants owing to inaccuracies in the tabulated values.

The optical properties of thin Sc films deposited in ultra high vacuum conditions have been investigated in the 6.7-174.4 nm spectral range. Transmittance and multi-angle reflectance were measured in situ in the 53.6-174.4 nm spectral range and they were used to obtain the complex refractive index of Sc films at every individual wavelength investigated. Transmittance measurements were made on Sc samples that were deposited over grids coated with a support C film. The transmittance and the extinction coefficient of Sc films at wavelengths shorter than 30 nm were measured ex situ. The ex situ samples were protected with an additional top C film before removal from vacuum. The transmittance characteristics of Sc films make them a potential candidate for EUV filters.

Scandium containing multilayers have been produced with very high reflectivity in the soft x-ray spectrum. Accurate optical constants are required in order to model the multilayer reflectivity. Since there are relatively few measurements of the optical constants of Scandium in the soft x-ray region we have performed measurements over the energy range of 50-1,300 eV. Thin films of Scandium were deposited by ion-assisted magnetron sputtering at Linkoping University and DC Magnetron sputtering at CXRO. Transmission measurements were performed at the Advanced Light Source beamline 6.3.2. The absorption coefficient was deduced from the measurements and the dispersive part of the index of refraction was obtained using the Kramers-Kronig relation. The measured optical constants are used to model the near-normal incidence reflectivity of Cr/Sc multilayers near the Sc L_2,3 edge.

We present optical constants derived from synchrotron reflectance measurements of iridium-coated X-ray witness mirrors over 0.05-12 keV, relevant to the Chandra X-ray Observatory effective area calibration. In particular we present for the first time analysis of measurements taken at the Advanced Light Source Beamline 6.3.2 over 50-1000 eV, Chandra's lower-energy range. Refinements to the currently tabulated iridium optical constants (B. L. Henke et al., At. Data Nucl. Data Tables 54, 181-343, 1993 and on the Web at http://www-cxro.lbl.gov/optical_constants/) will become important as the low-energy calibration of Chandra's X-ray detectors and gratings are further improved, and as possible contaminants on the Chandra mirror assembly are considered in the refinement of the in-flight Ir absorption edge depths. The goal of this work has been to provide an improved tabulation of the Ir optical constants over the full range of Chandra using a self-consistent mirror model, including metallic layers, interface roughness, contaminating overlayer, and substrate. The low-energy data present us with a considerable challenge in the modeling of the overlayer composition, as the K-absorption features of C, O, and N are likely to be present in the ~10A overlayer. The haphazard contamination and chemical shifts may significantly affect optical constants attributed to this overlayer, which will distort the iridium optical constants derived. Furthermore, the witness mirror contamination may be considerably different from that deposited on the flight optics. The more complex modeling required to deal with low-energy effects must reduce to the simpler model applied at the higher energies, which has successfully derived optical constants for iridium in the higher energy range, including the iridium M-edges, already used in the Chandra calibration. We present our current results, and the state of our modeling and analysis, and our approach to a self-consistent tabulation.

Ruthenium is one material that has been suggested for use in preventing the oxidation of Mo/Si mirrors used in extreme ultraviolet (EUV) lithography. The optical constants of Ru have not been extensively studied in the EUV. We report the complex index of refraction, 1 - δ + iβ, of sputtered Ru thin films from 11-14 nm as measured via reflectance and transmission measurements at the Advanced Light Source at Lawrence Berkley National Laboratory. Constants were extracted from reflectance data using the reflectance vs. incidence angle method and from the transmission data by Lambert’s law. We compare the measured indices to previously measured values. Our measured values for delta are between 14-18% less than those calculated from the atomic scattering factors (ASF) available from the Center for X-ray Optics (CXRO). Our measured values of beta are between 5-20% greater than the ASF values.

The use of coherent radiation from undulator beamlines has been used to directly measure the real and imaginary parts of the index of refraction of several metals1. Here we extend the same interferometric technique to slightly higher energies, and measure the indices of refraction of silicon and ruthenium, essential materials for extreme ultraviolet (EUV) lithography. Both materials are tested at-wavelength (13.4 nm.) Silicon is also measured about its L2 (99.8 eV) and L3 (99.2 eV) absorption edges. This measurement technique is currently being expanded further to soft X-ray wavelengths.

We have applied the x-ray extended-range technique (XERT) to measure mass attenuation coefficients over one order of magnitude more accurately than previously reported in the literature. We describe here the application of the XERT to the investigation of a number of systematic effects which has enabled us to ensure that these recent measurements are free from systematic error. In particular we describe our techniques for quantifying the effects of harmonic components in the x-ray beam, scattering and fluorescence from the absorbing sample, the bandwidth of the x-ray beam, and thickness variations across the absorber.

Uranium oxide and uranium nitride thin films reflect significantly more than all previously known/standard reflectors (e.g., nickel, gold, and iridium) for most of the 4-10 nm range at low angles of incidence. This work includes measurements of the EUV/soft x-ray (2-20 nm) reflectance of uranium-based thin films (~20 nm thick) and extraction of their optical constants (δ and β). We report the reflectances at 5, 10, and 15 degrees grazing incidence of air-oxidized sputtered uranium, reactively sputtered (O2) uranium oxide, and reactively sputtered (N2) uranium nitride thin films measured at Beamline 6.3.2 at the Advanced Light Source (ALS) at Lawrence Berkeley National Laboratory (LBNL). Additionally, we report optical constants of reactively sputtered uranium oxide at nine wavelengths from 4.6 to 17.5 nm derived from ALS angle-scan reflectance measurements. We also report optical constants of uranium nitride at 13 and 14 nm. We compare the reflectance of these uranium-compound thin films to gold, nickel (and nickel oxide), and iridium thin films from 2.5 to 11.6 nm. These metal thin films were chosen for comparison due to their wide use in EUV/soft x-ray applications as low-angle, thin-film reflectors. The uranium compounds can exhibit some surface oxidation in ambient air. There are important discrepancies between UO2’s and UN’s actual thin-film reflectance with those predicted from tabulated optical constants of the elemental constituents of the compounds. These differences are also demonstrated in the optical constants we report. Uranium-based optics applications have important advantages for zone plates, thin-film reflectors, and filters.

Transmission measurements of niobium and zirconium at both extreme-ultraviolet (EUV) and ultraviolet, visible, and near infrared (UV/Vis/NIR) wavelengths are presented. Thin foils of various thicknesses mounted on nickel mesh substrates were measured, and these data were used to calculate the optical constants delta and beta of the complex refractive index n = 1- δ + iβ. β values were calculated directly from the measured transmittance of the foils after normalizing for the nickel mesh. The average beta values for each set of foils are presented as a function of wavelength. The real (dispersive) part of the refractive index, delta was then calculated from Kramers-Kronig analysis by combining these beta values with those from previous experimental data and the atomic tables.

We discuss a first-principles method to compute electronic optical excitation spectra of solids over energy ranges varying from 20 eV to 70 eV. We discuss the principal components of the method that is used, which centers around solving the coupled electron-hole Bethe-Salpeter equation. Results are presented for the 1s edge of Si in silicon and F in LiF, as well as valence excitation spectra of BeO and MgO. We conclude by noting areas for future improvement.

By analyzing angle-dependent TEY spectra measured with fluorescence spectra, the depth-dependence of the absorbed energy in a Ru/B₄C reflection multilayer film was obtained as follows. The periodic multilayer structure was obtained as [Ru 24.38Å/B₄C 36.57Å] and [Ru 24.06Å/B₄C 36.09Å] by GIXRD and reflectance measurements respectively. The angles of incidence of the fluorescence spectra were determined as 16° and 41° using the angle dependent TEY spectra measured with the fluorescence spectra. The depth-dependence of the absorbed energy, which represents the intensity of the fluorescence spectrum, was calculated using these parameters. These results suggest that an angle-dependent TEY measurement can be used as an easy phase-determination method for standing waves that are generated by a reflection multilayer.

Approximately 40 different reservoir and surface rock samples were lased using high power COIL (1.315 micrometer), CO₂ (wavelength = 10.6 micrometer) and Nd:YAG (wavelength = 1.06 micrometer) lasers. Spectrum of the samples (sandstones, shales, and limestones) in the wavelength region from 0.35 to 15.387 wavelength were obtained. Spectral signatures and optic coefficients of the reservoir and surface sandstones were discussed by the authors in a previous paper (SPIE 5273-97). In this contribution, a detailed study of the spectral properties and optic signatures of shale and limestone samples is presented. The optic coefficients (extinction/reflection (E), scattering (S), absorption (K) and emission (F)) of these rocks are mathematically and statistically calculated and are critically investigated against rock chemistry, grain size, porosity, cementing matrix and rock textures, and total organic content. Our investigations show that: 1) Porosity and grain size are the only rock properties that exhibited a strong statistical relation with the absorption and reflection coefficients. 2) Rocks with high porosity have greater reflection coefficients (at the COIL and Nd:YAG wavelengths) compared to those having lower porosity. 3) The reflectance at the CO2 laser wavelength (10.6 wavelength) is not a function of porosity or grain size. 4) Surface and reservoir shales have almost the same spectral features and hence similar optic coefficients. This indicates that mode of occurrence does not influence the spectral signatures of rocks. 5) Spectrum of limestones is dominated by the four (v₁ v₂, v₃, and v₄) fundamental stretching carbonate absorption bands.

Characterization of optical materials and components is one of the major tasks for the Radiometry Laboratory of the Physikalisch-Technische Bundesanstalt, Germany's national metrology institute, at the synchrotron radiation source BESSY II. Using spectrally dispersed synchrotron radiation, reflectometry measurements have been performed on highly pure CaF2 crystals in the VUV spectral region between 90 nm and 130 nm wavelength in the vicinity of the absorption edge. Here, the optical constants are influenced by an excitonic resonance directly correlated to the recently found anisotropy of the crystal at 157-nm wavelength. To investigate temperature-dependent effects, the reflectometer sample holder has been equipped with a heater/cooler stage, which currently enables measurements at stable temperatures in the range between -50° C and 80° C.

We investigated the optical properties of titanium dioxide (TiO₂) thin films which were deposited by ion beam assisted deposition (IAD) method on crystalline silicon and acrylic substrates. TiO₂ thin films were grown by different growing conditions which are used the conditions of vacuum pressure, and deposition rate. The controlled vacuum pressure were 3 x 10^-5Torr and 3 x 10^-6 Torr, and the deposition rate was controlled to 0.35 nm/second, 0.20 nm/second, and 0.12 nm/second. Measurements of spectroscopic ellipsometry were performed in the spectral range between 0.76 eV and 8.7 eV with 0.02 eV steps and at the angle of incidence of 75°. We determined the complex refractive index and thickness of TiO₂ thin films using the optical model which is included the Tauc-Lorentz dispersion equation and compared the relations between the optical properties and deposition rate or vacuum pressure variation. The optical band gaps of TiO₂ thin films are around 3.42 eV.