Empirical relations among scattering, roughness parameters, and thickness of aluminum films

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 AmericaPeer Reviewe

Optical coatings for the spectral range 50 – 200 nm

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.Mónica Fernández Perea agradece al Consejo Superior de Investigaciones Científicas la financiación a través del programa de becas predoctorales I3P.Peer reviewe

Self-consistent optical constants of MgF2,LaF3, and CeF3 films

18 pags., 11 figs., 3 tabs.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.Spanish Programa Estatal de Investigación Científica y Técnica de Excelencia, Secretaría de Estado de Investigación, Desarrollo e Innovación (AYA2013-42590-P and ESP2016-76591-P).Peer Reviewe

Narrowband filters for the FUV range

10 págs.; 6 figs.; 4 tabs.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: Coatings, Far Ultraviolet, Atmosphere Physics, Transmittance Filters, Space OpticsThis research was partly supported by the National Programme for Research, Subdirección General de Proyectos de Investigación, Ministerio de Ciencia e Innovación, project number AYA2010-22032 and AYA2013- 42590-P. The authors are gratefully acknowledged to Pedro Valdivieso (Instalación de irradiación Náyade, CIEMAT).Peer Reviewe

Electron-beam deposited boron coatings for the extreme ultraviolet

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 AmericaThis work was supported by the National Programme for Space Research, Subdirección General de Proyectos de Investigación, Ministerio de Ciencia y Tecnología, project number ESP2005-02650. M. Fernández-Perea is thankful to Consejo Superior de Investigaciones Científicas (Spain) for funding under the Programa I3P (Ref. I3P-BPD2004) partially supported by the European Social Fund. We acknowledge the technical assistance of José M. Sánchez-Orejuela. M. Vidal-Dasilva is thankful to Ministerio de Educación y Ciencia for funding under the FPI BES-2006- 14047 fellowship.Peer Reviewe

Optical constants of evaporation-deposited silicon monoxide films in the 7.1-800 eV photon energy range

8 págs.; 11 figs.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.This work was supported by the National Programme for Space Research, Subdirección General de Proyectos de Investigación, Ministerio de Ciencia y Tecnología, Project Nos. ESP2002-01391 and ESP2005-02650. This work was also performed under the auspices of the U.S. Department of Energy by the University of California Lawrence Berkeley National Laboratory under Contract No. DE-AC03-76F00098 and by the University of California Lawrence Livermore National Laboratory under Contract No. DE-AC52- 07NA27344. M.F.-P. is thankful to Consejo Superior de Investigaciones Científicas Spain for funding under the Programa I3P Contract No. I3P-BPD2004, partially supported by the European Social Fund. M.V.-D. acknowledges financial support from a FPI Contract No. BES-2006-14047 fellowship.Peer Reviewe

VUV reflectometer for in-situ measurement of coatings

290. PTB-Seminar, VUV and EUV Metrology, Berlin-Charlottenburg, Berlin, November 5th - 6th, 2015; http://www.euv2015.ptb.de/euv2015/euv2015-home.htmlAbstract comunicación póster: GOLD¿s reflectometer enables measuring absolute reflectance and transmittance versus incidence angle mainly in the 40-190 nm spectral range. VUV lines are generated with a windowless discharge lamp. The lamp is fed with various pure gases or gas mixtures with which it can generate many spectral lines to cover the spectral range of interest. The reflectometer chamber is connected in vacuum with two deposition chambers, one operating by evaporation and the other by ion-beam sputtering. Hence the reflectance/transmittance of a thin film or a multilayer can be measured in situ before the coating is exposed to the atmosphere. The combination of evaporation and sputtering permits the deposition of a wide range of materials. The two deposition chambers and the main reflectometer chamber operate in UHV conditions. In the presentation, examples of measurements performed with the reflectometer will be displayed. The reflectometer, covering an unusual spectral range, is offered to the community.Peer Reviewe

Transmittance and optical constants of ca films in the 4-1000 eV spectral range

8 págs.; 8 figs.; OCIS codes: (260.7200) Ultraviolet, extreme; (120.4530) Optical constants; (350.2450) Filters, absorption; (230.4170) Multilayers; (310.6860) Thin films, optical properties.© 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 acknowledge support by the European Community—Research Infrastructure Action under the FP6 “Structuring the European Research Area” Programme (through the Integrated Infrastructure Initiative “Integrating Activity on Synchrotron and Free Electron Laser Science”) through proposal number Ref. 2007655. This work was also supported by the National Programme for Space Research, Subdirección General de Proyectos de Investigación, Ministerio de Ciencia y Tecnología, project numbers AYA2010-22032 and AYA2013-42590-P. L. Rodrí- guez-de Marcos and S. García-Cortés are thankful to Consejo Superior de Investigaciones Científicas (CSIC) for funding under the Programa JAE, partially supported by the European Social Fund. M. Vidal-Dasilva acknowledges financial support from an FPI fellowship number BES-2006-14047Peer Reviewe

Nonoxidized Al-overcoated Ir bilayers with high reflectance in the extreme ultraviolet above 50 nm

7 pages, 6 figures.-- PACS: 42.79.Wc; 78.66.Bz; 78.20.Ci; 95.55.-n; 81.15.Ef; 81.40.Gh; 81.40.Tv; 78.40.KcBilayers 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.This work was performed under financial support No. ESP1999-1763-E from the National Program for Space Research through Spanish Comisión Interministerial de Ciencia y Tecnología.Peer reviewe

Electron microscopy of transformations produced in GeTe thin films by irradiation

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.We give sincere thanks to Mr. Jos6 M. S•nchez-Orejuela for his technical assistance. We are also indebted to Dr. J. M. Palacios who carried out the energy- dispersive X-ray microanalysis.Peer Reviewe