This study reports development and testing of coatings on silicon pore optics (SPO) substrates including pre and post coating characterisation of the x-ray mirrors using Atomic Force Microscopy (AFM) and X-ray reflectometry (XRR) performed at the 8 keV X-ray facility at DTU Space and with synchrotron radiation in the laboratory of PTB at BESSY II. We report our findings on surface roughness and coating reflectivity of Ir/B4C coatings considering the grazing incidence angles and energies of ATHENA and long term stability of Ir/B4C, Pt/B4C, W/Si and W/B4C coatings.
In this paper, we present a route for making smart functionalized plastic parts by injection molding with sub-micrometer
surface structures. The method is based on combining planar processes well known and established within silicon micro
and sub-micro fabrication with proven high resolution and high fidelity with truly freeform injection molding inserts.
The link between the planar processes and the freeform shaped injection molding inserts is enabled by the use of
nanoimprint with flexible molds for the pattern definition combined with unidirectional sputter etching for transferring
the pattern. With this approach, we demonstrate the transfer of down to 140 nm wide holes on large areas with good
structure fidelity on an injection molding steel insert. The durability of the sub-micrometer structures on the inserts have
been investigated by running two production series of 102,000 and 73,000 injection molded parts, respectively, on two
different inserts and inspecting the inserts before and after the production series and the molded parts during the
Structural colors are optical phenomena of physical origin, where microscale and nanoscale structures determine the reflected spectrum of light. Artificial structural colors have been realized within recent years. However, multilayer structures require substantial fabrication. Instead we considered one-layer surface textures of silicon. We explored four patterns of square structures in a square lattice with periods of 500, 400, 300, and 200 nm. The reflectivity and daylight-colors were measured and compared with simulations based on rigorously coupled-wave analysis with excellent agreement. Based on the 200-nm periodic pattern, it was found that angle-independent specular colors up to 60 deg of incidence may be provided. The underlying mechanisms include (1) the suppression of diffraction and (2) a strong coupling of light to localized surface states. The strong coupling yields absorption anomalies in the visual spectrum, causing robust colors to be defined for a large angular interval. The result is a manifestation of a uniformly defined color, similar to pigment-based colors. These mechanisms hold potential for color engineering and can be used to explain and predict the structural-color appearance of silicon-based textures for a wide range of structural parameters.
We present description and results of the test campaign performed on Silicon Pore Optics (SPO) samples to
be used on the ATHENA mission. We perform a pre-coating characterization of the substrates using Atomic
Force Microscopy (AFM), X-ray Re
ectometry (XRR) and scatter measurements. X-ray tests at DTU Space and
correlation between measured roughness and pre-coating characterization are reported. For coating development,
a layer of Cr was applied underneath the Ir/B4C bi-layer with the goal of reducing stress, and the use of N2
during the coating process was tested in order to reduce the surface roughness in the coatings. Both processes
show promising results. Measurements of the coatings were carried out at the 8 keV X-ray facility at DTU
Space and with synchrotron radiation in the laboratory of PTB at BESSY II to determine re
ectivity at the
grazing incidence angles and energies of ATHENA. Coating development also included a W/Si multilayer coating.
We present preliminary results on X-ray Re
ectometry and Cross-sectional Transmission Electron Microscopy
(TEM) of the W/Si multilayer.
We present an innovative method Optical Diffraction Microscopy (ODM). for the simultaneous measurement of specular and non-specular diffraction patterns of sub-micron periodic structures. A sample is illuminated with broadband light and the diffraction pattern is collected by using a pair of ellipsoidal mirrors, optical fibers and a spectrometer. This method allows for rapid measurements and makes used of the Rigorous Coupled Wave algorithm for data analysis. In the present work the method has been applied to binary and multi-layer sub-micron gratings. A series of binary gratings with periods of 318 nm and 360 nm with different exposure levels of the photoresist were investigated. We succeded in characterize underexposed, ideally exposed and overexposed photoresist grating profiles. The measurements are well-suited to determine the delivered exposure energy density to photoresist gratings. The ODM technique may thus be applied to specify the exposure window and as a feedback in order to adjust the exposure energy density on-line. The homogeneity of a grating on multi-layered substrate has been investigated. Heights and duty cycles ranging from 50 nm to 55 nm and 0.25 to 0.97, respectively, have been found. AFM measurements of the gratings verify the ODM results and demonstrate that the ODM technique can be used to determine grating topology.
Atomic force microscopy (AFM) and optical diffraction microscopy (ODM) are used to measure the profiles of grating grooves with depths much larger than their widths. Gratings with these features are essential in numerous optical devices such as spectrometers, monochromators and for the production of many fibre Bragg gratings. However, measurement of the physical shape is inherently difficult but necessary for the understanding of their function and in order to improve the manufacturing process. After a thorough calibration of an AFM and by tilting the plane of the grating by up to 17° relative to the symmetry axis of the sensing probe we measured accurately and traceably the sidewall angle and the sidewall profile in a non-destructive way. ODM is a new method where the intensity of the optical field diffracted is measured as a function of the frequency and an inverse algorithm is used to reconstruct the surface profile. It is fast, non-destructive, and it gives height and filling degree of a grating very accurately. As example a high aspect ratio grating with period p of 220 nm, depths d of ≈300 nm, and sidewall angles
γ of approximately ≈90° and filling degree f of ≈40 % were examined. Standard uncertainties as low as u(d) = 3 nm, u( α) = 0.4° and u(f) = 3.1 % were achieved. Despite the fact that the AFM responds to the physical surface and ODM responds to the optical
properties of the material we find that the results are in very good agreement and consistent with (destructive) scanning electron microscopy measurements of the filling degree.
Atomic force microscopy (AFM) and interference microscopy are two methods often used to measure roughness, but the probe size is very different and they respond to different physical properties (hardness and reflectivity). In earlier work we have shown that the limited resolution of interference microscopy can be approximated by the longwave components of a Gaussian filtering of the AFM image with a cut-off wavelength λc a little larger than the wavelength of light. This description was valid for smooth and hard surfaces with good reflectivity such as polished metal surfaces (Rq < 10 nm). In this paper we extent the analysis to directly measure the effective cut-off wavelength λc = 2600 nm for a particular interference microscope based on the profiles of grooves with a period of 3000 nm, a depth of (104 ± 1) nm and vertical sidewalls. To validate the measured parameter λc, the same area on a polished hip joint prosthesis was measured by both an AFM and the particular interference microscope. Without a Gaussian filtering of the AFM image the appearance and calculated roughness of the images were significantly different (Ra = 1.7 nm, Rq = 2.2 nm versus Ra = 1.0 nm, Rq = 1.2 nm). However, using the measured cut-off wavelength the visual appearance of the longwave components of the AFM image and the interference microscope image are almost identical and the calculated roughness is equal. This strongly suggests that an effective cut-off wavelength can be measured and used to give consistency between the different methods in the range where they overlap.