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Comprende: - una parrilla (10, 11) que está formada por una pluralidad de hilos (12) de metal refractario que están yuxtapuestos uno al lado de otro en paralelo, estando la parrilla (10, 11) destinada a soportar una cantidad de un material evaporante (13) fundido, para ser evaporado en vacío con el fin de formar un depósito en forma de lámina delgada, donde los hilos (12) comprenden dos extremos; y dos casquillos de conexión (14), localizados en ios extremos, y que mantienen unidos todos los hilos (12) entre sí, y facilitan la conexión de los hilos (12) con una fuente de electricidad. Se puede emplear una parrilla recta (10), con hilos (12) rectos, o una parrilla curvada (11), con hilos (12) que presentan una parte curvada formando una diferencia de nivel (R). [EN], The invention relates to a resistive heat source comprising: an array (10, 11) formed by a plurality of wires (12) of refractory metal that are juxtaposed side by side in parallel, the array (10, 11) being intended to support an amount of molten evaporating material (13) to be vacuum evaporated to form a thin film deposit, wherein the wires (12) comprise two ends; and two connection caps (14) located at the ends, which keep all the wires (12) joined together and facilitate the connection of the wires (12) to an electricity source. A straight array (10) with straight wires (12) or a curved array (11) with wires (12) having a curved part forming a difference of level (R) can be used. [EN]

Fuente térmica de tipo resistivo para deposición de láminas delgadas mediante evaporación en vacío. Comprende: - una parrilla (10, 11) que está formada por una pluralidad de hilos (12) de metal refractario que están yuxtapuestos uno al lado de otro en paralelo, estando la parrilla (10, 11) destinada a soportar una cantidad de un material evaporante (13) fundido, para ser evaporado en vacío con el fin de formar un depósito en forma de lámina delgada, donde los hilos (12) comprenden dos extremos; y dos casquillos de conexión (14), localizados en los extremos, y que mantienen unidos todos los hilos (12) entre sí, y facilitan la conexión de los hilos (12) con una fuente de electricidad. Se puede emplear una parrilla recta (10), con hilos (12) rectos, o una parrilla curvada (11), con hilos (12) que presentan una parte curvada formando una diferencia de nivel (R).

More ecient and stable far ultraviolet (FUV) mirrors will enable future space observatories. Traditional FUV mirrors are based on MgF2-protected Al. AlF3 has been identified as a promising substitute for MgF2 to prevent Al oxidation. Hence, the reflectivity, stability, and morphology of AlF3-protected Al mirrors have been investigated as a function of deposition temperature of the AlF3 film. In this work, it is shown how AlF3 deposition temperature is an important parameter whose optimization ultimately yields valuable throughput enhancement and improved endurance to large storage periods. Al films were deposited at room temperature (RT) and AlF3 protective layers were deposited at temperatures ranging from RT to 350 C. It was found that the optimum AlF3 deposition temperature was between 200 and 250 C, yielding the largest FUV reflectance and a better stability of the mirrors, which had been stored in a desiccator environment. Increasing AlF3 deposition temperature resulted in an increase in film density, approaching bulk density at 250 C. The morphology of Al and AlF3 films as a function of AlF3 deposition temperature was also investigated. The increase in the AlF3 deposition temperature resulted in a decrease of both Al and AlF3 surface roughness and in the growth of the grain width at the AlF3 outer surface. It also resulted in a trend for the prevalent (111) planes of Al nanocrystals to orient parallel to the coating surface.

More efficient and stable far ultraviolet (FUV) mirrors will enable future space observatories. Traditional FUV mirrors are based on MgF2-protected Al. AlF3 has been identified as a promising substitute for MgF2 to prevent Al oxidation. Hence, the reflectivity, stability, and morphology of AlF3-protected Al mirrors have been investigated as a function of deposition temperature of the AlF3 film. In this work, it is shown how AlF3 deposition temperature is an important parameter whose optimization ultimately yields valuable throughput enhancement and improved endurance to large storage periods. Al films were deposited at room temperature (RT) and AlF3 protective layers were deposited at temperatures ranging from RT to 350 °C. It was found that the optimum AlF3 deposition temperature was between 200 and 250 °C, yielding the largest FUV reflectance and a better stability of the mirrors, which had been stored in a desiccator environment. Increasing AlF3 deposition temperature resulted in an increase in film density, approaching bulk density at 250 °C. The morphology of Al and AlF3 films as a function of AlF3 deposition temperature was also investigated. The increase in the AlF3 deposition temperature resulted in a decrease of both Al and AlF3 surface roughness and in the growth of the grain width at the AlF3 outer surface. It also resulted in a trend for the prevalent (111) planes of Al nanocrystals to orient parallel to the coating surface.

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.

Polarimetry is a valuable technique to help us understand the role played by the magnetic field of the coronal plasma in the energy transfer processes from the inner parts of the Sun to the outer space. Polarimetry in the far ultraviolet (FUV: 100-200 nm), which must be performed from space due to absorption in terrestrial atmosphere, supplies fundamental data of processes that are governed by the Doppler and Hanle effects on resonantly scattered line-emission. To observe these processes there are various key spectral lines in the FUV, from which H I Lyman ¿ (121.6 nm) is the strongest one. Hence some solar physics missions that have been proposed or are under development plan to perform polarimetry at 121.6 nm, like the suborbital missions CLASP I (2015) and CLASP II (2018), and the proposed solar missions SolmeX and COMPASS and stellar mission Arago. Therefore, the development of efficient FUV linear polarizers may benefit these and other possible future missions. C IV (155 nm) and Mg II (280 nm) are other spectral lines relevant for studies of solar and stellar magnetized atmospheres. High performance polarizers can be obtained with optimized coatings. Interference coatings can tune polarizers at the spectral line(s) of interest for solar and stellar physics. Polarizing beamsplitters consist in polarizers that separate one polarization component by reflection and the other by transmission, which enables observing the two polarization components simultaneously with a single polarizer. They involve the benefit of a higher efficiency in collection of polarization data due to the use of a single polarizer for the two polarization components and they may also facilitate a simplified design for a space polarimeter. We present results on polarizing beamsplitters tuned either at 121.6 nm or at the pair of 155 and 280 nm spectral lines. © (2017) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use o

Polarimetry is a valuable technique to help us understand the role played by the magnetic field of the coronal plasma in the energy transfer processes from the inner parts of the Sun to the outer space. Polarimetry in the far ultraviolet (FUV: 100-200 nm), which must be performed from space due to absorption in terrestrial atmosphere, supplies fundamental data of processes that are governed by the Doppler and Hanle effects on resonantly scattered line-emission. To observe these processes there are various key spectral lines in the FUV, from which H I Lyman ¿ (121.6 nm) is the strongest one. Hence some solar physics missions that have been proposed or are under development plan to perform polarimetry at 121.6 nm, like the suborbital missions CLASP I (2015) and CLASP II (2018), and the proposed solar missions SolmeX and COMPASS and stellar mission Arago. Therefore, the development of efficient FUV linear polarizers may benefit these and other possible future missions. C IV (155 nm) and Mg II (280 nm) are other spectral lines relevant for studies of solar and stellar magnetized atmospheres. High performance polarizers can be obtained with optimized coatings. Interference coatings can tune polarizers at the spectral line(s) of interest for solar and stellar physics. Polarizing beamsplitters consist in polarizers that separate one polarization component by reflection and the other by transmission, which enables observing the two polarization components simultaneously with a single polarizer. They involve the benefit of a higher efficiency in collection of polarization data due to the use of a single polarizer for the two polarization components and they may also facilitate a simplified design for a space polarimeter. We present results on polarizing beamsplitters tuned either at 121.6 nm or at the pair of 155 and 280 nm spectral lines.

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

Polarimetry is a powerful tool to interpret how the coronal plasma is involved in the energy transfer processes from the Sun¿s inner parts to the outer space. Space polarimetry in the far ultraviolet (FUV) provides essential information of processes governed by the Doppler and Hanle resonant electron scattering effects. Among the key FUV spectral lines to observe these processes, H I Lyman ¿ (121.6 nm) is the most intense. Some developing or proposed solar physics missions, such as CLASP, SolmeX, and COMPASS, plan to perform polarimetry at 121.6 nm. Classical solutions, such as a parallel plate of a transparent material, either MgF2 or LiF, result in a modest efficiency of the passing polarization component. The development of more efficient linear polarizers at this wavelength will benefit future space instruments. A research has been conducted to develop polarizers based on (Al/MgF2)n multilayer coatings in a band containing 121.6 nm, to obtain a significant efficiency increase over plates. Coatings operating by reflectance resulted in a high efficiency after approximately one year of storage under nitrogen. In parallel, coating polarizers operating by transmittance have been prepared for the first time. Transmissive polarizers have the advantage that they involve no deviation of the beam. As a further benefit, the developed transmittance polarizers additionally incorporate filtering properties to help reject wavelengths both shortwards and longwards of a band containing 121.6 nm. Hence a polarizer combined with a filter is obtained with a single device. The combined polarizer-filter could enable a higher performance polarimeter for solar physics if the use of a separate filter to isolate Lyman ¿ turns unnecessary

© 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.

We address the design, fabrication, and characterization of transmittance filters for the Ionosphere Photometer instrument (IP), developed by the Center for Space Science and Applied Research (CSSAR). IP, a payload of Feng-Yun 3D meteorological satellite, to be launched on 2016, is aimed to perform photometry measurements of Earth¿s ionosphere by the analysis of the OI (135.6 nm) spectral line and N2 Lyman-Birge-Hopfield (LBH, 140-180 nm) band, both of them in the far ultraviolet (FUV) range. The most convenient procedure to isolate a spectral band is the use of tunable transmittance filters. In many applications the intensity of the ultraviolet, visible and infrared background is higher than the intensity of the target FUV lines; therefore one of the most important requirements for transmittance filters is to reject (by reflecting and/or by absorbing) as efficiently as possible the visible and close ranges. In the FUV range, (Al/MgF2)n transmittance filters are the most common, and they are suitable to reject the visible and adjacent ranges. These materials present unique properties in this range: MgF2 is transparent down to ~115 nm and Al has a very low refractive index in the FUV that contrasts well with MgF2. Narrowband tunable filters with very low transmittance at long wavelengths are achievable. The main data on the preparation and characterization of IP filters by Grupo de Óptica de Láminas Delgadas (GOLD) is detailed. In this proceeding we present (Al/MgF2)3 filters peaked at either 135.6 nm or at the center of the LBH band (~160 nm). Filters were characterized in the 125-800 nm range (143-800 nm range for the LBH filter). After some storage in a desiccator, both coatings kept a transmittance of ~0.14 at their target wavelengths, with visible-topeak transmittance ratios of 1.2·10-4 (OI filter) and 1.3·10-4 (LBH filter). One filter tuned at each target wavelength was exposed to ~300 Gy 60Co gamma dose, with no significant transmittance change. Keywords: Coat

Multilayer coatings in the far UV (FUV) are required for various fields of application, such as space instrumentation for astrophysics, solar physics and atmosphere physics, as well as free electron lasers, plasma diagnostics, synchrotron radiation, spectroscopy, etc. In order to design the desired multilayer, accurate optical constants of the materials are required. Several fluorides are among the materials in nature that keep their transparency down to the short FUV, which makes them almost the only choice for multilayer coatings tuned in the ~100-150-nm wavelength range. The optical constants of thin films of MgF2, LaF3, and CeF3 have been determined in the spectral range of 30-950 nm. Among them, MgF2 is a low refractive index material whereas LaF3 and CeF3 have a relatively high refractive index at short wavelengths; this contrast is adequate to make multilayer coatings. Fluoride thin films were deposited by evaporation onto substrates at 523 K. Optical constants were calculated using sets of transmittance, reflectance, and ellipsometry measurements. The measured optical constants were extended to a broader range with literature data and extrapolations in order to obtain self-consistent sets of data using the Kramers-Krönig analysis. The optical constant data here presented extend the available literature data both shortwards and longwards, particularly for CeF3 where few data had been reported. The obtained optical constants of MgF2 and LaF3 were used to design narrowband reflective multilayer coatings for the short FUV. Multilayer coatings centered at 121 and at 130 nm with remarkable reflectance were prepared. The coatings kept a valuable reflectance after ageing in a desiccator for 12 months. © (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

Space observations in the far ultraviolet (FUV, 100-200 nm) are aimed at providing essential information for astrophysics, solar physics, and atmosphere physics. There are key spectral lines and bands in the FUV for the above disciplines. Despite various developments in the recent decades, yet many observations are not possible due to technical limitations, of which one of the most important is the lack of efficient optical coatings. Hence for solar physics applications there are needs of narrowband coatings for key wavelengths such as H Lyman ß (102.6 nm) and OVI lines (103.2 and 103.8 nm). For atmosphere physics, narrowband coatings are required for observations at spectral lines such as OI (135.6 nm) and at the N2 Lyman-Birge-Hopfield band (LBH, 127-240 nm). In solar corona observations, often the intensities of the target lines are weak, and this radiation may be masked by more intense lines, such as H Lyman ¿ at 121.6 nm. Until now, no narrowband multilayers peaked in the ~100-105 nm range have been reported, which is due to the absorption of materials at these wavelengths. When efficient narrowband coatings are not possible, an option is the use of coatings with high reflectance at the target wavelength and simultaneously low reflectance at the undesired wavelength, such as Lyman ¿. We have developed novel multilayers to address this target, with combinations of these materials: Al, LiF, SiC and C. We developed multilayers based on the following three systems, Al/LiF/SiC, Al/LiF/SiC/C, and Al/LiF/SiC/LiF. Their reflectance was measured both when fresh and after some storage in a desiccator. Al/LiF/SiC and Al/LiF/SiC/C systems displayed a high Lyman ß/Lyman ¿ reflectance ratio when fresh, although they resulted in an undesired reflectance increase at Lyman ¿ for the aged samples and the reflectance ratio Lyman ß/Lyman ¿ became small; this behavior turned these systems useless for the present application. The most promising multilayers were the ones based on the

Space observations in the far ultraviolet (FUV, 100-200 nm) are aimed at providing essential information for astrophysics, solar physics, and atmosphere physics. There are key spectral lines and bands in the FUV for the above disciplines. Despite various developments in the recent decades, yet many observations are not possible due to technical limitations, of which one of the most important is the lack of efficient optical coatings. Hence for solar physics applications there are needs of narrowband coatings for key wavelengths such as H Lyman ß (102.6 nm) and OVI lines (103.2 and 103.8 nm). For atmosphere physics, narrowband coatings are required for observations at spectral lines such as OI (135.6 nm) and at the N2 Lyman-Birge-Hopfield band (LBH, 127-240 nm). In solar corona observations, often the intensities of the target lines are weak, and this radiation may be masked by more intense lines, such as H Lyman ¿ at 121.6 nm. Until now, no narrowband multilayers peaked in the ~100-105 nm range have been reported, which is due to the absorption of materials at these wavelengths. When efficient narrowband coatings are not possible, an option is the use of coatings with high reflectance at the target wavelength and simultaneously low reflectance at the undesired wavelength, such as Lyman ¿. We have developed novel multilayers to address this target, with combinations of these materials: Al, LiF, SiC and C. We developed multilayers based on the following three systems, Al/LiF/SiC, Al/LiF/SiC/C, and Al/LiF/SiC/LiF. Their reflectance was measured both when fresh and after some storage in a desiccator. Al/LiF/SiC and Al/LiF/SiC/C systems displayed a high Lyman ß/Lyman ¿ reflectance ratio when fresh, although they resulted in an undesired reflectance increase at Lyman ¿ for the aged samples and the reflectance ratio Lyman ß/Lyman ¿ became small; this behavior turned these systems useless for the present application. The most promising multilayers were the ones based on the

GOLD’s research is devoted to the development of novel coatings for the far (100-200 nm, FUV) and the extreme (40-100 nm, EUV) ultraviolet, and it is mostly focused on applications for space optics. Developments include high reflectance mirrors, narrowband coatings, filters, and polarizers. GOLD covers all stages from multilayer design and material optical characterization to multilayer deposition and FUV-EUV optical measurements. These stages are completed with the capacity to coat relatively large substrates in clean-room conditions to meet space requirements. GOLD has been involved on filters for WSO’s imaging instrument for over a decade. In the presentation, an overview of GOLD’s capacities to prepare and characterize FUV filters will be given, along with a summary of coatings that are relevant to space optics.

The transmittance and the optical constants of SrF2 thin films, a candidate material for multilayer coatings operating in the extreme ultraviolet and soft x-rays, have been determined in the spectral range of 25¿780¿eV, in most of which no experimental data were previously available. SrF2 films of various thicknesses were deposited by evaporation onto room-temperature, thin Al support films, and their transmittance was measured with synchrotron radiation. The transmittance as a function of film thickness was used to calculate the extinction coefficient k at each photon energy. A decrease in density with increasing SrF2 film thickness was observed. In the calculation of k, this effect was circumvented by fitting the transmittance versus the product of thickness and density. The real part of the refractive index of SrF2 films was calculated from k with Kramers-Krönig analysis, for which the measured spectral range was extended both to lower and to higher photon energies with data in the literature combined with interpolations and extrapolations. With the application of f- and inertial sum rules, the consistency of the compiled data was found to be excellent. . VC 2013 American Institute of Physics.

Permite el desarrollo de un filtro de banda estrecha que cubre las longitudes de onda de la región espectral del ultravioleta extremo (UVE) entre aproximadamente 50 y 100 nm, proporcionando un recubrimiento que puede reflejar una banda estrecha con mayor reflectancia en el máximo de la banda que cualquier otro filtro existente. Dicho filtro de banda estrecha destaca fundamentalmente porque comprende al menos una lámina de Eu interna, una lámina de Al y una lámina de Eu externa, depositadas sobre un soporte formando una estructura multicapa. Dicha estructura multicapa se encuentra protegida por una lámina protectora preferentemente de SiO, estando las láminas de Eu y Al separadas por unas láminas barrera.

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.

The optical constants n and k of holmium (Ho) films were obtained in the 3-1340-eV range from transmittance measurements performed at room temperature. Thin films of Ho with various thicknesses were deposited by evaporation in ultra high vacuum conditions and their transmittance was measured in situ. Ho films were deposited onto thin C-film substrates supported on high transmittance grids. Transmittance measurements were used to obtain the extinction coefficient k of Ho films. The refractive index n of Ho was calculated with Kramers-Krönig analysis; in order to do this, k data were extrapolated both on the high and on the low energy parts of the spectrum by using experimental and calculated k values available in the literature. Ho, similar to other lanthanides, has a low-absorption band below the O2,3 edge onset; the lowest absorption was measured at ∼22 eV. Therefore, Ho is a promising material for filters and multilayer coatings in the energy range below the O2,3 edge in which most materials have a large absorption. Good consistency of the data resulted from the application of f and inertial sum rules. © 2011 American Institute of Physics.

The experimental study of the optical properties of thin carbon films to be used as grazing-incidence coatings for extreme-ultraviolet high-order harmonics is presented. The carbon samples were deposited on plane glass substrates by the electron beam evaporation technique. The optical constants (real and imaginary parts of the refraction index) have been calculated through reflectivity measurements. The results are in good agreement with what reported in the literature, and confirm that carbon-coated optics operated at grazing incidence have a remarkable gain over conventional metallic coatings in the extreme ultraviolet. Since the harmonics co-propagate with the intense infrared laser generating beam, the carbon damage threshold when exposed to ultrashort infrared laser pulses has been measured.

The optical constants n and k of lutetium (Lu) films were obtained in the 3-1800 eV range from transmittance measurements performed at room temperature. These are the first experimental optical constant data of Lu in the whole range. Thin films of Lu with various thicknesses were deposited by evaporation in ultrahigh vacuum conditions and their transmittance was measured in situ. Lu films were deposited onto grids coated with a thin, C support film. Transmittance measurements were used to obtain the extinction coefficient k of Lu films. The refractive index n of Lu was calculated with Kramers-Krönig analysis. k data were extrapolated both on the high and on the low-energy sides by using experimental and calculated k values available in the literature. Lu, similar to other lanthanides, has a low-absorption band below the O 2,3 edge onset; the lowest absorption was measured at ∼25.1 eV. Therefore, Lu is a promising material for filters and multilayer coatings in the energy range below the O2,3 edge in which most materials have a large absorption. Good consistency of the data was obtained through f and inertial sum rules. © 2010 American Institute of Physics.

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.

The transmittance of silicon monoxide films prepared by thermal evaporation was measured from 7.1 to 800 eV and used to determine the optical constants of the material. SiO films deposited onto C-coated microgrids in ultrahigh vacuum conditions were measured in situ from 7.1 to 23.1 eV. Grid-supported SiO films deposited in high vacuum conditions were characterized ex situ from 28.5 to 800 eV. At each photon energy, transmittance, and thickness data were used to calculate the extinction coefficient k. The obtained k values combined with data from the literature, and with interpolations and extrapolations in the rest of the electromagnetic spectrum provided a complete set of k values that was used in a Kramers-Kronig analysis to obtain the real part of the index of refraction, n. Two different sum-rule tests were performed that indicated good consistency of the data. © 2009 American Institute of Physics.

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

The development of efficient optical coatings in the spectral region between 50 and 200 nm (EUV-FUV) is an important challenge due to the great absortion and low reflectance that most of the materials present in this region. In addition, these coatings are an important element in the advance of many fields like astronomical abservations, plasma diagnosis and lithography. In this work we describe some of the optical coatings developed by the Research Group in Thin Film Coatings (GOLD), which operate in the EUV-FUV region of the spectrum. In GOLD we have an ultra high vacuum experimental system that permits the deposition and in situ measurement of the transmittance and reflectance of multilayers, as a function of the angle of incidence, and in the EUV-FUV spectral range. We prepare multilayers with up to six different materials, which can be deposited using three different techniques. In situ transmittance and reflectance measurements versus the angle of incidence permits the determination of the optical constants (n,k) of the materials, without being exposed to the atmosphere. Due to the great dependance between the optical properties of thin film layers in this spectral range, and the exposition to the atmosphere, our experimental system is a very adequate tool for the determination of those properties, and therefore for the design and fabrication of novel multilayers., El desarrollo de recubrimientos ópticos eficientes en la región espectral comprendida entre 50 y 200 nm (UVE-UVL) supone un reto debido a la gran absorción y baja reflectancia que presentan la mayoría de los materiales en este intervalo. Por otro lado estos recubrimientos son una pieza importante para el progreso de multitud de campos como las observaciones astronómicas, el diagnóstico de plasmas y la litografía. En este trabajo se describen algunos de los recubrimientos ópticos desarrollados hasta el momento por el Grupo de investigación en Óptica de Láminas Delgadas (GOLD), que operan en la región UVE-UVL del espectro. En GOLD disponemos de un equipo experimental de ultra-alto vacío que permite la deposición y medida in situ de la transmitancia y la reflectancia de multicapas en función del ángulo de incidencia y en el rango espectral UVL-UVE. Las multicapas están formadas por hasta seis materiales distintos, que pueden ser depositados mediante tres técnicas de preparación diferentes. Las medidas de transmitancia y reflectancia en función del ángulo de incidencia realizadas in situ permiten la determinación de las constantes ópticas (n, k) de los materiales sin que hayan sido expuestos a la atmósfera. Dada la gran dependencia existente entre las propiedades ópticas de las láminas delgadas y la exposición atmosférica en este rango espectral, nuestro equipo experimental constituye una herramienta muy adecuada para su determinación, y por lo tanto para el diseño y preparación de multicapas innovadoras.

The scaling exponents of interface width and coarsening of evaporated gold films with thickness from 30 to 1800 nm were obtained from two-dimensional measurements on scanning tunneling microscopy (STM) images and are presented here. The lateral size of protrusion on the surface of the films increases with a constant scaling exponent n1/3. The interface width grows in two stages. The final stage starts at 60 nm and corresponds to a time scaling exponent of 1/3 with a constant slope morphology. Scaling exponents are compared with those from models for high thickness epitaxial growth and for polycrystalline film growth, all predict a constant slope morphology. To help the choice among the three compatible models, STM results are compared with transmission electron microscopy (TEM) images where low contrast structures can be observed on large crystalline plates. As a result it may be interpreted that the structures observed correspond either to a mound growth or to an array of columns with low grain boundaries between them. Other smaller crystalline components are observed in polycrystalline areas and can be assigned to columnar tops. The practically unimodal Gaussian distribution of local heights, indicates that the surface morphologies arising from these two bulk structural components are not very different and suggests that both morphologies are controlled by the same atomic surface diffusion phenomena.

Bilayers of a thin, nonoxidized Al film over an Ir film are prepared. The bilayers are intended to enhance the reflectance of Al below the Al plasma wavelength ((landa)p~83 nm). Above (landap) the bilayers have a high reflectance comparable to that of single Al films. Ir films were deposited by electron gun evaporation on a heated substrate. Al films of various thicknesses are deposited by evaporation from a thermal source on the Ir film once it is cooled to room temperature. The bilayers are prepared under ultra-high-vacuum (UHV) conditions and their reflectance is measured in situ. Accelerated aging processes, which are performed by annealing the bilayers in UHV, show that the bilayers are stable after 1 h annealing at temperatures up to 540±25 K. The bilayers show no observable deterioration after long-term storage under normal atmosphere. The optical constants of Ir films are also obtained. In-orbit coating of optical surfaces with Ir/Al bilayers is proposed for extreme UV astronomy.

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

We have studied by electron microscopy and selected area diffraction the morphology and structure of the different oxides which are obtained by air-burning of a filament of molybdenum. The electron microscopy observation shows several morphologies depending on the filament temperature and the pressure of the oxidation vessel. Experimental pressures of 100, 300, 600 and 700 Torr were used and, for each, the temperature ranged from 650 to 1250°C. Platelets, needles, mosaic and spheroids have been the most frequent microcrystal shapes. Orthorhombic MoO3 and Mo4O11 structures have been identified. The oxide formation evolves from needles and mosaic (at lowest pressure and temperature) to spheroids (at the highest ones). © 1980.

© 1987

The depth of Vickers microindentations in high density, low density and linear low density polyethylenes has been studied by two wave interferometry. The evolution of the delayed depth recovery is explained in terms of the Burgers model of viscoelastic behaviour and the numerical parameters associated with the model are related to the crystallinity, elastic modulus and yield stress of the polyethylenes studied. © 1988 Chapman and Hall Ltd.

Amorphous thin films of two different Ge-Te alloys were prepared by simultaneous evaporation in vacuum. Morphological and structural transformations produced in the films by laser or electron beam irradiation were studied using transmission electron microscopy and selected area electron diffraction. As the irradiation power is increased minute microcrystals are segregated followed by crystallization of the whole irradiated spot, and finally a hole surrounded by a crystalline rim is formed. Digital information can be recorded on these Ge-Te films as bright or dark spots by using open holes or crystalline spots respectively. © 1985.