Single-layer mirrors for advanced research light sources

Störmer, M.; Horstmann, C.; Siewert, Frank; Scholze, Frank; Krumrey, Michael; Hertlein, Frank; Matiaske, M.; Wiesmann, J.; Gaudin, J.

doi:10.1063/1.3463321

Cited by 9 publications

(8 citation statements)

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“…This is quite a high value at about 94% of the bulk density of 2.52 g cm À3 (Thé venot, 1990). This is in agreement with previous results (Stö rmer et al, 2010Kozhevnikov et al, 2015). In comparison with magnetron sputtering, other thin-film methods are not able to achieve such a high density.…”

Section: à3supporting

confidence: 82%

“…The critical angle is determined by photon energy and the density of the coating material. The combination of magnetron-sputtered amorphous carbon (a-C) on a silicon substrate works reliably in the soft X-ray range at FLASH (Tiedtke et al, 2009;Stö rmer et al, 2010). For hard X-rays, a promising coating material is boron carbide (B 4 C) because it contains light elements and has a high melting point of about 2400 C (Thé venot, 1990).…”

Section: Introductionmentioning

confidence: 99%

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Preparation and characterization of B₄C coatings for advanced research light sources

Störmer

Siewert

Sinn

2016

J Synchrotron Radiat

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X-ray optical elements are required for beam transport at the current and upcoming free-electron lasers and synchrotron sources. An X-ray mirror is a combination of a substrate and a coating. The demand for large mirrors with single layers consisting of light or heavy elements has increased during the last few decades; surface finishing technology is currently able to process mirror lengths up to 1 m with microroughness at the sub-nanometre level. Additionally, thin-film fabrication is able to deposit a suitable single-layer material, such as boron carbide (B 4 C), some tens of nanometres thick. After deposition, the mirror should provide excellent X-ray optical properties with respect to coating thickness errors, microroughness values and slope errors; thereby enabling the mirror to transport the X-ray beam with high reflectivity, high beam flux and an undistorted wavefront to an experimental station. At the European XFEL, the technical specifications of the future mirrors are extraordinarily challenging. The acceptable shape error of the mirrors is below 2 nm along the whole length of 1 m. At the Helmholtz-Zentrum Geesthacht (HZG), amorphous layers of boron carbide with thicknesses in the range 30-60 nm were fabricated using the HZG sputtering facility, which is able to cover areas up to 1500 mm long by 120 mm wide in one step using rectangular B 4 C sputtering targets. The available deposition area is suitable for the specified X-ray mirror dimensions of upcoming advanced research light sources such as the European XFEL. The coatings produced were investigated by means of X-ray reflectometry and interference microscopy. The experimental results for the B 4 C layers are discussed according to thickness uniformity, density, microroughness and thermal stability. The variation of layer thickness in the tangential and sagittal directions was investigated in order to estimate the achieved level of uniformity over the whole deposition area, which is considerably larger than the optical area of a mirror. A waisted mask was positioned during deposition between the sputtering source and substrate to improve the thickness uniformity; particularly to prevent the formation a convex film shape in the sagittal direction. Additionally the inclination of the substrate was varied to change the layer uniformity in order to optimize the position of the mirror quality deposited area during deposition. The level of mirror microroughness was investigated for different substrates before and after deposition of a single layer of B 4 C. The thermal stability of the B 4 C layers on the various substrate materials was investigated.

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Section: à3supporting

confidence: 82%

Section: Introductionmentioning

confidence: 99%

Preparation and characterization of B₄C coatings for advanced research light sources

Störmer

Siewert

Sinn

2016

J Synchrotron Radiat

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“…3.8 mrad, which means that the film density of the magnetronsputtered B 4 C layer is 2.37 g cm À3 and this is 94% from the bulk value of 2.52 g cm À3 (Thé venot, 1990). Previous results are in good agreement (Stö rmer et al, 2010(Stö rmer et al, , 2011(Stö rmer et al, , 2016aKozhevnikov et al, 2015).…”

Section: Results and Discussion Of Fel Coatingssupporting

confidence: 80%

Coatings for FEL optics: preparation and characterization of B₄C and Pt

et al. 2018

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Large X-ray mirrors are required for beam transport at both present-day and future free-electron lasers (FELs) and synchrotron sources worldwide. The demand for large mirrors with lengths up to 1 m single layers consisting of light or heavy elements has increased during the last few decades. Accordingly, surface finishing technology is now able to produce large substrate lengths with micro-roughness on the sub-nanometer scale. At the Helmholtz-Zentrum Geesthacht (HZG), a 4.5 m-long sputtering facility enables us to deposit a desired single-layer material some tens of nanometers thick. For the European XFEL project, the shape error should be less than 2 nm over the whole 1 m X-ray mirror length to ensure the safe and efficient delivery of X-ray beams to the scientific instruments. The challenge is to achieve thin-film deposition on silicon substrates, benders and gratings without any change in mirror shape. Thin films of boron carbide and platinum with a thickness in the range 30-100 nm were manufactured using the HZG sputtering facility. This setup is able to cover areas of up to 1500 mm Â 120 mm in one step using rectangular sputtering sources. The coatings produced were characterized using various thin-film methods. It was possible to improve the coating process to achieve a very high uniformity of the layer thickness. The movement of the substrate in front of the sputtering source has been optimized. A variation in B 4 C layer thickness below 1 nm (peak-to-valley) was achieved at a mean thickness of 51.8 nm over a deposition length of 1.5 m. In the case of Pt, reflectometry and micro-roughness measurements were performed. The uniformity in layer thickness was about 1 nm (peak-to-valley). The micro-roughness of the Pt layers showed no significant change in the coated state for layer thicknesses of 32 nm and 102 nm compared with the uncoated substrate state. The experimental results achieved will be discussed with regard to current restrictions and future developments.

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“…Since the mean layer thicknesses are higher than 45 nm for Ni and B 4 C and lower than 35 nm for C, it has to be changed in the final deposition according to the specified thickness range. The measured high level of uniformity confirms former results using the HZG magnetron sputtering facility 5,9 .Previous investigations of tungsten and carbon coatings reached similar uniformity in thickness. Here, the goal was to coat a very large aperture of 1500 mm x 120 mm.…”

Section: Thickness Uniformity Of Single Layerssupporting

confidence: 75%

“…Before deposition onto the 820 mm long Si substrates, a lot of short calibration samples were coated over various areas to determine X-ray optical film properties such as thickness, density and roughness. The sputtering facility 9 enables us to coat a lot of substrates fixed on a carrier over an area of 1500 mm x 120 mm. Furthermore, the positions and dimensions of the required stripes of single layers were measured, controlled and adjusted to fulfill the technical requirements as mentioned below.…”

Section: Methodsmentioning

confidence: 99%

Preparation and characterization of x-ray mirrors with three single layers of a-C, B₄C, and Ni onto two 820-mm long Si substrate

et al. 2014

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Single-layer mirrors for advanced research light sources

Cited by 9 publications

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Preparation and characterization of B₄C coatings for advanced research light sources

Preparation and characterization of B₄C coatings for advanced research light sources

Coatings for FEL optics: preparation and characterization of B₄C and Pt

Preparation and characterization of x-ray mirrors with three single layers of a-C, B₄C, and Ni onto two 820-mm long Si substrate

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Single-layer mirrors for advanced research light sources

Cited by 9 publications

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Preparation and characterization of B4C coatings for advanced research light sources

Preparation and characterization of B4C coatings for advanced research light sources

Coatings for FEL optics: preparation and characterization of B4C and Pt

Preparation and characterization of x-ray mirrors with three single layers of a-C, B4C, and Ni onto two 820-mm long Si substrate

Contact Info

Product

Resources

About

Preparation and characterization of B₄C coatings for advanced research light sources

Preparation and characterization of B₄C coatings for advanced research light sources

Coatings for FEL optics: preparation and characterization of B₄C and Pt

Preparation and characterization of x-ray mirrors with three single layers of a-C, B₄C, and Ni onto two 820-mm long Si substrate