Ritva A. M. Keski-Kuha

Normal incidence reflectance of ion beam deposited SiC films in the EUV

Results are presented from an experimental investigation of the normal-incidence reflectance at 58.4, 92.0, and 121.6 nm wavelength of 30- and 80-nm-thick SiC films produced by ion-beam deposition on unheated 5 x 5-cm microscope slides. The films were deposited in the 2-m evaporator described by Bradford et al. (1969) with chamber base pressure 1 microtorr, operating pressure 40 microtorr, and a 50-62-mA 750-eV Ar ion beam; the reflectance measurements were obtained in the reflector-monochromator system described by Osantowski (1974). Reflectances of over 30 percent were found at 92 and 121.6 nm, almost equal to those of polished CVD films of SiC and degrading only slightly after aging for 4 months. It is suggested that ion-beam deposition may be the best low-temperature technique for coating EUV optics for space astronomy.

Layered synthetic microstructure technology considerations for the extreme ultraviolet

The performance of layered synthetic microstructures (LSMs) in the extreme ultraviolet (EUV), particularly in the 300-A spectral region, has been evaluated. Representative designs were analyzed, and experimental mirror coatings were produced. Pt–Si and Ir–Si combinations clearly demonstrate that the enhancement can be realized over a limited bandwidth of 75 A. Preliminary results for the Ir–Si combination on a diffraction grating indicate that LSMs enhance grating efficiencies in the EUV by a factor of ~3.

Far ultraviolet optical properties of MgF2 films deposited by ion-beam sputtering and their application as protective coatings for Al

Abstract Thin films of MgF2 deposited by evaporation is a material widely used for its transparency in the far ultraviolet (FUV) down to ∼115 nm. In this paper the optical properties of ion-beam sputtered (IBS) MgF2 in the FUV are investigated and compared with MgF2 films deposited by evaporation. A slightly higher transparency at the 121.6-nm, H Lyman α line was obtained for IBS MgF2 films compared to films deposited by evaporation, which makes IBS MgF2 a promising protective material for Al reflective coatings. Experimental work on Al films that were protected with a thin evaporated MgF2 film followed by an IBS MgF2 film to produce a protective coating with optimum thickness showed a reflectance at 121.6 nm that was higher by about 3% compared to an Al film protected with an all-evaporated MgF2 film.

Ion-beam-deposited boron carbide coatings for the extreme ultraviolet.

The normal-incidence reflectance of ion-beam-deposited boron carbide thin films has been evaluated in the extreme ultraviolet (EUV) spectral region. High-reflectance coatings have been produced with reflectances greater than 30% between 67 and 121.6 nm. This high reflectance makes ion-beam-deposited boron carbide an attractive coating for EUV applications.

Multilayer coatings with high reflectance in the extreme-ultraviolet spectral range of 50 to 121.6 nm

Multilayer coatings with three layers were designed to yield an increase in normal-incidence reflectance in the extreme ultraviolet over that of the available single-layer coatings. Multilayer coatings based on Al, MgF(2), and either SiC or B(4)C were demonstrated to have higher reflectance than single layers of SiC and B(4)C in the spectral region from 57.9 nm to the H Lyman-alpha line (121.6 nm) and above. The increase in reflectance was higher at wavelengths close to 121.6 nm. Reflectance degraded slightly over time in the same way as for single layers. After a few months, multilayer coatings maintained higher reflectance than their single-layer counterparts.

Reflectance measurements and optical constants in the extreme ultraviolet for thin films of ion-beam-deposited SiC, Mo, Mg 2 Si, and InSb and of evaporated Cr

Reflectance measurements and optical constants of thin films of ion-beam-deposited SiC, Mo, Mg(2)Si, and InSb and of evaporated Cr have been measured in the extreme-ultraviolet (EUV) spectral region from 49.0 to 200.0 nm. In this spectral region no optical constant data were available for materials deposited by ion-beam deposition. We compared our data with those for bulk samples and for thin films prepared by different techniques. The goal of this research has been to study candidate materials for multilayer coatings in the EUV.

Metalized polyimide filters for x-ray astronomy and other applications

Filters fabricated from metalized polyimide have been specified for a number of x-ray astronomy missions, including the Advanced X-ray Astrophysics Facility (AXAF), the x-ray spectrometer (XRS) on Astro-E, the Advanced Composition Explorer (ACE), and the Geostationary Operational Environmental Satellite (GOES). Polyimide offers greater strength, improved temperature stability, and effectiveness in blocking unwanted ultraviolet radiation compared to polymeric films previously employed. This paper reviews the various x- ray astronomy missions and the particular challenges that were met with polyimide filters. The paper also reviews the development of free standing thin foils of polyimide with mechanical properties optimized for x-ray astronomy and other applications, such as synchrotron research.

Optical coating technology for the EUV

Abstract Advances in optical coating and materials technology have been one of the key motivators for the development of missions such as the Far Ultraviolet Spectroscopic Explorer recently selected by NASA for an Explorer class mission in the mid 1990s. We review the performance of a range of candidate coatings for normal incidence and glancing incidence applications, and discuss strengths and problem areas for their use in space. The importance of recent developments in multilayer films, chemical vapor deposited SiC (CVD-SiC) mirrors, and SiC films are discussed in the context of EUV instrumentation design. For example, the choice of optical coatings is a design driver for the selection of the average glancing angle for the FUSE telescope, and impacts efficiency, short wavelength cut-off, and physical size.

Reflectance measurements and optical constants in the extreme ultraviolet of thin films of ion-beam-deposited carbon

Abstract Reflectance measurements of ion-beam-deposited (IBD) C films were performed in the extreme ultraviolet (EUV) spectral region from 49 to 200 nm. Near normal incidence reflectance of IBD C films was determined to be higher than that of evaporated C films but lower than that of diamond. Optical constants of IBD C films were obtained from reflectance measurements as a function of the angle of incidence in the spectral range 49.0–121.6 nm. The relatively high reflectance of IBD C films in the spectral region 49–92 nm and its stability when stored in a desiccator make it an interesting coating material for the EUV.

Optical properties of hot-pressed B 4 C in the extreme ultraviolet

Hot-pressed B(4)C is found to have a high normal reflectance in the extreme-UV spectral region above 49 nm. This reflectance is comparable with or higher than chemical-vapor-deposited SiC in the spectral region from 49 to 92 nm. Reflectance measurements as a function of the angle of incidence yielded the optical constants of B(4)C in the spectral range 49-121.6 nm.Hot-pressed B(4)C is found to have a high normal reflectance in the extreme-UV spectral region above 49 nm. This reflectance is comparable with or higher than chemical-vapor-deposited SiC in the spectral region from 49 to 92 nm. Reflectance measurements as a function of the angle of incidence yielded the optical constants of B(4)C in the spectral range 49-121.6 nm.