Fabrication of laser deposited high-quality multilayer zone plates for hard X-ray nanofocusing

Eberl, Christian; Döring, Florian; Liese, Tobias; Schlenkrich, Felix; Roos, B.; Hahn, Matthias; Hoinkes, Thomas; Rauschenbeutel, Arno; Osterhoff, Markus; Salditt, Tim; Krebs, Hans‐Ulrich

doi:10.1016/j.apsusc.2014.04.089

Cited by 40 publications

(9 citation statements)

References 23 publications

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“…Here we briefly describe the fabrication of MZPs using pulsed laser deposition (PLD) and focused ion beam (FIB); for more details, see [5].…”

Section: Fabricationmentioning

confidence: 99%

“…We note that the stoichiometry on a fibre is even different from a planar substrate. The precise composition is crucial to calculate the indices of refraction determining the optical thickness [5].…”

Section: Pulsed Laser Depositionmentioning

confidence: 99%

“…Also, focussing of X-rays above 30 keV is today only possible using compound refractive lenses (CRLs), that achieve few µm spot sizes at these energies. Fresnel Zone Plates, known from soft X-ray optics [Schmahl], have been generalised to Multilayer Zone Plates and Multilayer Laue Lenses, that can be fabricated with an optical thickness of many µm, and hence are promising candidates for efficient focusing of ≥ 60 keV to spot sizes below 100 nm [1][2][3][4][5][6][7].…”

Section: Introductionmentioning

confidence: 99%

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Ultra-high-aspect multilayer zone plates for even higher x-ray energies

Osterhoff

Soltau

Eberl

et al. 2017

Advances in X-Ray/Euv Optics and Components XII

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Penetration lengths in the millimetre range make hard x-rays above 60 keV a well-suited tool for non-invasive probing of small specimens buried deep inside their surroundings, and enable studying individual components inside assembled, complex devices (solar cells, batteries etc.). The real-space resolution of typical imaging modalities like fluorescence mapping, scanning SAXS and WAXS depend on the available beam size. Although routine in the 5-25 keV regime [1-4], spot sizes below 50 nm are very challenging at x-ray energies above 50 keV: Compound refractive lenses lack in refractive power, the multilayer thickness of coated mirrors is bounded by interfacial diffusion, and lithographic Fresnel Zone Plates loose their efficiency in the two-digit keV regime. Multilayer Laue Lenses and Multilayer Zone Plates (MZP) are promising candidates for high-keV focusing to small spot sizes; compared to Fresnel Zone Plates, the aspect ratio comparing outermost layer width (~focal spot size) to optical thickness (efficiency) is virtually unlimited by the fabrication. Using Pulsed Laser Deposition on a rotating wire (several millimetre long), we have fabricated an MZP with 10 nm outermost zone widths and optical thickness of 30 µm (optimum phase shift at 60 keV), yielding an unprecedented ultra-high aspect ratio of 1:3000 (outermost zone width compared to optical thickness). We present experimental results obtained at ESRF's high energy beamline ID31, where for the first time scanning experiments with real-space resolutions below 50 nm even at x-ray energies ranging from 60 keV to above 100 keV have been achieved.

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“…Here we briefly describe the fabrication of MZPs using pulsed laser deposition (PLD) and focused ion beam (FIB); for more details, see [5].…”

Section: Fabricationmentioning

confidence: 99%

Section: Pulsed Laser Depositionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Ultra-high-aspect multilayer zone plates for even higher x-ray energies

Osterhoff

Soltau

Eberl

et al. 2017

Advances in X-Ray/Euv Optics and Components XII

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“…The ML-FZPs are fabricated via a bottom-up film growth approach. In the process a cylindrical core is coated with two alternating materials using sputtering [25,26,29], pulsed laser [30], chemical vapor [31,32] or atomic layer deposition (ALD) [28]. The resulting multilayer is sliced and polished to deliver the ML-FZPs.…”

Section: Introductionmentioning

confidence: 99%

Overview of the multilayer-Fresnel zone plate and the kinoform lens development at MPI for intelligent systems

et al. 2015

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The ultimate goal of our research is to develop novel fabrication methods for high efficiency and high resolution X-ray optics. To this end, we have been pursuing the fabrication of several innovative diffractive/refractive optics designs. One such optic is the multilayer type Fresnel zone plate (ML-FZP). Our fabrication process relies on the atomic layer deposition (ALD) of two materials on a smooth glass fiber followed by a focused ion beam (FIB) based slicing and polishing. The ALD process allows much smaller outermost zone widths than the standard electron beam lithography based FZPs, meaning FZPs with potentially higher resolutions. Moreover, by depositing the multilayer on a cm long glass-fiber FZPs with very high optical thicknesses can be fabricated that can efficiently focus harder X-rays as well. A 21 nm half-pitch resolution was achieved using the ML-FZPs. Another optic we have been working on is the kinoform lens, which is a refractive/diffractive optic with a 100 % theoretical focusing efficiency. Their fabrication is usually realized by using approximate models which limit their success. Recently the fabrication of real kinoform lenses has been successfully realized in our lab via gray-scale direct-write ion beam lithography without any approximations. The lenses have been tested in the soft X-ray range achieving up to ~90 % of the calculated efficiency which indicates outstanding replication of the designed profile. Here we give an overview of our research and discuss the future challenges and opportunities for these optics.

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“…High aspect ratio nano-structures can also be fabricated by other techniques like MACE (Metal Assisted Chemical Etching) in combination with line-doubling [14], multilayer lenses [15][16][17][18] or by stacking [19]. However, reaching the highest possible aspect ratio is not in the focus of this manuscript.…”

Section: Introductionmentioning

confidence: 99%

Systematic efficiency study of line-doubled zone plates

Marschall

Vila‐Comamala

Guzenko

et al. 2017

Microelectronic Engineering

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Line-doubled Fresnel zone plates provide nanoscale, high aspect ratio structures required for efficient high resolution imaging in the multi-keV x-ray range. For the fabrication of such optics a high aspect ratio HSQ resist template is produced by electron-beam lithography and then covered with Ir by atomic layer deposition (ALD).The diffraction efficiency of a line-doubled zone plate depends on the width of the HSQ resist structures as well as on the thickness of the deposited Ir layer. It is very difficult to measure these dimensions by inspection in a scanning electron microscope (SEM) without performing laborious and destructive cross-sections by focus ion beams (FIB). On the other hand, a systematic measurement of the diffraction efficiencies using synchrotron radiation in order to optimize the fabrication parameters is not realistic, as access to synchrotron radiation is sparse.We present a fast and reliable method to study the diffraction efficiency using filtered radiation from an X-ray tube with a copper anode, providing an effective spectrum centered around 8 keV. A large number of Fresnel zone plates with varying dimensions of the resist structures and the ALD coating were measured in an iterative manner. Our results show an excellent match with model calculations. Moreover, this systematic study enables us to identify the optimum fabrication parameters, resulting in a significant increase in diffraction efficiency compared to Fresnel zone plates fabricated earlier without having feedback from a systematic efficiency measurement.

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Fabrication of laser deposited high-quality multilayer zone plates for hard X-ray nanofocusing

Cited by 40 publications

References 23 publications

Ultra-high-aspect multilayer zone plates for even higher x-ray energies

Ultra-high-aspect multilayer zone plates for even higher x-ray energies

Overview of the multilayer-Fresnel zone plate and the kinoform lens development at MPI for intelligent systems

Systematic efficiency study of line-doubled zone plates

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