Maria Scholz - Academia.edu (original) (raw)

Papers by Maria Scholz

 Users may download and print one copy of any publication from the public portal for the purpose... more  Users may download and print one copy of any publication from the public portal for the purpose of private study or research.  You may not further distribute the material or use it for any profit-making activity or commercial gain  You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

Journal of Applied Crystallography, 2020

Ptychographic X-ray imaging at the highest spatial resolution requires an optimal experimental en... more Ptychographic X-ray imaging at the highest spatial resolution requires an optimal experimental environment, providing a high coherent flux, excellent mechanical stability and a low background in the measured data. This requires, for example, a stable performance of all optical components along the entire beam path, high temperature stability, a robust sample and optics tracking system, and a scatter-free environment. This contribution summarizes the efforts along these lines to transform the nanoprobe station on beamline P06 (PETRA III) into the ptychographic nano-analytical microscope (PtyNAMi).

Microscopy and Microanalysis, 2018

Microscopy and Microanalysis, 2018

Ptychography has become a key tool for high-resolution X-ray microscopy. We present here an exten... more Ptychography has become a key tool for high-resolution X-ray microscopy. We present here an extension to it that allows to work with insufficiently sampled diffraction patterns and reconstructs previously unseen parts of the sample. In ptychographic imaging the sample is scanned through a coherent beam recording the intensity distribution of the transmitted scattered wavefield at each scanpoint. Based on the ensemble of diffraction patterns and redundant information in adjacent diffraction patterns, ptychography retrieves the complex-valued transmission function of the sample. At the same time, also the illuminating probe is reconstructed in amplitude and phase. Due to this, the ptychography reconstructions are independent of any aberrations from the optics and the spatial resolution is not limited by the numerical aperture of the optics. Today, resolutions in the hard X-ray regime of 30 nm down to 10 nm are routinely achieved. One of the most popular ptychographic algorithms, ePIE [1], now has many extensions to deal with different experimental conditions, for example for thick, non-planar objects a multislice variant was proposed [2]. One extension concerns the influence of the detector on the measured diffraction patterns. A detector pixel integrates the number of photons over its area. A speckle can only be properly sampled, if it extends over multiple pixels. When the speckles are of the same size or smaller than a pixel, the sampling theorem is not fulfilled resulting in loss of information that leads to artefacts in the reconstruction. The up-sampling ptychographic iterative engine (sPIE), however, is able to reconstruct sample and probe even when the speckle are smaller than one pixel [3]. Due to the reciprocal relationship between distances in the sample plane and the detector plane and accordingly between the size of the probe and the resulting speckles, small speckles correspond to a large probe and vice versa. We demonstrate that sPIE can be used for aberrated focusing optics, which produce a larger-than-designed probe, and that this larger probe allows for the reconstruction of hitherto unseen parts of the sample outside of the original field of view.

Journal of Synchrotron Radiation, 2018

Wavefront errors of rotationally parabolic refractive X-ray lenses made of beryllium (Be CRLs) ha... more Wavefront errors of rotationally parabolic refractive X-ray lenses made of beryllium (Be CRLs) have been recovered for various lens sets and X-ray beam configurations. Due to manufacturingviaan embossing process, aberrations of individual lenses within the investigated ensemble are very similar. By deriving a mean single-lens deformation for the ensemble, aberrations of any arbitrary lens stack can be predicted from the ensemble with \bar{\sigma} = 0.034λ. Using these findings the expected focusing performance of current Be CRLs are modeled for relevant X-ray energies and bandwidths and it is shown that a correction of aberrations can be realised without prior lens characterization but simply based on the derived lens deformation. The performance of aberration-corrected Be CRLs is discussed and the applicability of aberration-correction demonstrated over wide X-ray energy ranges.

Journal of Instrumentation, 2018

The nature of retinal shielding pigment in the larval eyes of the midge Clunio marinus was studie... more The nature of retinal shielding pigment in the larval eyes of the midge Clunio marinus was studied by high resolution scanning X-ray fluorescence (XRF) analysis correlated with light microscopy (LM) and scanning coherent X-ray diffractive imaging (Ptychography). Clunio is known as a unique model system to decipher mechanisms underlying the complex moon-related rhythms. Shielding pigment granules within the photoreceptor cells of their primitive eyes (ocelli) have been shown to change appearance in the same rhythm. We compared the relative amount of trace metals (Ca, Ni, Zn, Cu), obtained by XRF, within single melanosomes (diameter about 500 nm) and the surrounding photoreceptor cells with their optical density in the light microscope and - for the first time - the electron density derived from the ptychography measurements. Though individual pigment granules can be identified and correlated in images of all three techniques the optical density, electron density and especially element concentrations within individual granules seem to vary independently. We discuss that the state of melanogenesis is not synchronized inside the ocellus

Microscopy and Microanalysis, 2018

Nature Communications, 2017

Due to their short wavelength, X-rays can in principle be focused down to a few nanometres and be... more Due to their short wavelength, X-rays can in principle be focused down to a few nanometres and below. At the same time, it is this short wavelength that puts stringent requirements on X-ray optics and their metrology. Both are limited by today's technology. In this work, we present accurate at wavelength measurements of residual aberrations of a refractive X-ray lens using ptychography to manufacture a corrective phase plate. Together with the fitted phase plate the optics shows diffraction-limited performance, generating a nearly Gaussian beam profile with a Strehl ratio above 0.8. This scheme can be applied to any other focusing optics, thus solving the X-ray optical problem at synchrotron radiation sources and X-ray freeelectron lasers.

Applied Physics Letters, 2017

Broadband optical absorption based on single-sized metal-dielectric-metal plasmonic nanostructure... more Broadband optical absorption based on single-sized metal-dielectric-metal plasmonic nanostructures with high-ε ″ metals Appl.

Advances in X-Ray/EUV Optics and Components XII, 2017

We developed a corrective phase plate that enables the correction of residual aberration in refle... more We developed a corrective phase plate that enables the correction of residual aberration in reflective, diffractive, and refractive X-ray optics. The principle is demonstrated on a stack of beryllium compound refractive lenses with a numerical aperture of 0.49 × 10 −3 at three different synchrotron radiation and x-ray free-electron laser facilities. By introducing this phase plate into the beam path, we were able to correct the spherical aberration of the optical system and improve the Strehl ratio of the optics from 0.29(7) to 0.87(5), creating a diffraction-limited, large aperture, nanofocusing optics that is radiation resistant and very compact.

The hard x-ray scanning microscope at beamline P06 of PETRA III at DESY in Hamburg serves a large... more The hard x-ray scanning microscope at beamline P06 of PETRA III at DESY in Hamburg serves a large user community, from physics, chemistry, and nanotechnology to the bio-medical, materials, environmental, and geosciences. It has been in user operation since 2012, and is mainly based on nanofocusing refractive x-ray lenses. Using refractive optics, nearly gaussian-limited nanobeams in the range from 50 to 100 nm can be generated in the hard x-ray energy range from 8 to 30 keV. The degree of coherence can be traded off against the flux in the nanobeam by a two-stage focusing scheme. We give a brief overview on published results from this instrument and describe its most important components and parameters.

Microscopy and Microanalysis, 2016

A new closed cell is presented forin situX-ray ptychography which allows studies under gas flow a... more A new closed cell is presented forin situX-ray ptychography which allows studies under gas flow and at elevated temperature. In order to gain complementary information by transmission and scanning electron microscopy, the cell makes use of a Protochips E-chipTMwhich contains a small, thin electron transparent window and allows heating. Two gold-based systems, 50 nm gold particles and nanoporous gold as a relevant catalyst sample, were used for studying the feasibility of the cell. Measurements showing a resolution around 40 nm have been achieved under a flow of synthetic air and during heating up to temperatures of 933 K. An elevated temperature exhibited little influence on image quality and resolution. With this study, the potential ofin situhard X-ray ptychography for investigating annealing processes of real catalyst samples is demonstrated. Furthermore, the possibility to use the same sample holder forex situelectron microscopy before and after thein situstudy underlines the un...

Applied Physics Letters, 2014

Advances in X-Ray/EUV Optics and Components VIII, 2013

Hard x-ray scanning microscopy relies on small and intensive nanobeams. Refractive x-ray lenses a... more Hard x-ray scanning microscopy relies on small and intensive nanobeams. Refractive x-ray lenses are well suited to generate hard x-ray beams with lateral dimensions of 100 nm and below. The diffraction limited beam size of refractive x-ray lenses mainly depends on the focal length and the attenuation inside the lens material. The numerical aperture of refractive lenses scales with the inverse square root of the focal length until it reaches the critical angle of total reflection. We have used nanofocusing refractive x-ray lenses made of silicon to focus hard x-rays at 8 and 20 keV to (sub-)100 nm dimensions. Using ptychographic scanning coherent diffraction imaging we have characterized these nanobeams with high accuracy and sensitivity, measuring the full complex wave field in the focus. This gives access to the full caustic and aberrations of the x-ray optics.

SPIE Proceedings, 2016

Due to the weak interaction of X-rays with matter and their small wavelength on the atomic scale,... more Due to the weak interaction of X-rays with matter and their small wavelength on the atomic scale, stringent requirements are put on X-ray optics manufacturing and metrology. As a result, these optics often suffer from aberrations. Until now, X-ray optics were mainly characterized by their focal spot size and efficiency. However, both measures provide only insufficient information about optics quality. Here, we present a quantitative analysis of residual aberrations in current beryllium compound refractive lenses using ptychography followed by a determination of the wavefront error and subsequent Zernike polynomial decomposition. Known from visible light optics, we show that these measures can provide an adequate tool to determine and compare the quality of various X-ray optics.

 Users may download and print one copy of any publication from the public portal for the purpose... more  Users may download and print one copy of any publication from the public portal for the purpose of private study or research.  You may not further distribute the material or use it for any profit-making activity or commercial gain  You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

Journal of Applied Crystallography, 2020

Ptychographic X-ray imaging at the highest spatial resolution requires an optimal experimental en... more Ptychographic X-ray imaging at the highest spatial resolution requires an optimal experimental environment, providing a high coherent flux, excellent mechanical stability and a low background in the measured data. This requires, for example, a stable performance of all optical components along the entire beam path, high temperature stability, a robust sample and optics tracking system, and a scatter-free environment. This contribution summarizes the efforts along these lines to transform the nanoprobe station on beamline P06 (PETRA III) into the ptychographic nano-analytical microscope (PtyNAMi).

Microscopy and Microanalysis, 2018

Microscopy and Microanalysis, 2018

Ptychography has become a key tool for high-resolution X-ray microscopy. We present here an exten... more Ptychography has become a key tool for high-resolution X-ray microscopy. We present here an extension to it that allows to work with insufficiently sampled diffraction patterns and reconstructs previously unseen parts of the sample. In ptychographic imaging the sample is scanned through a coherent beam recording the intensity distribution of the transmitted scattered wavefield at each scanpoint. Based on the ensemble of diffraction patterns and redundant information in adjacent diffraction patterns, ptychography retrieves the complex-valued transmission function of the sample. At the same time, also the illuminating probe is reconstructed in amplitude and phase. Due to this, the ptychography reconstructions are independent of any aberrations from the optics and the spatial resolution is not limited by the numerical aperture of the optics. Today, resolutions in the hard X-ray regime of 30 nm down to 10 nm are routinely achieved. One of the most popular ptychographic algorithms, ePIE [1], now has many extensions to deal with different experimental conditions, for example for thick, non-planar objects a multislice variant was proposed [2]. One extension concerns the influence of the detector on the measured diffraction patterns. A detector pixel integrates the number of photons over its area. A speckle can only be properly sampled, if it extends over multiple pixels. When the speckles are of the same size or smaller than a pixel, the sampling theorem is not fulfilled resulting in loss of information that leads to artefacts in the reconstruction. The up-sampling ptychographic iterative engine (sPIE), however, is able to reconstruct sample and probe even when the speckle are smaller than one pixel [3]. Due to the reciprocal relationship between distances in the sample plane and the detector plane and accordingly between the size of the probe and the resulting speckles, small speckles correspond to a large probe and vice versa. We demonstrate that sPIE can be used for aberrated focusing optics, which produce a larger-than-designed probe, and that this larger probe allows for the reconstruction of hitherto unseen parts of the sample outside of the original field of view.

Journal of Synchrotron Radiation, 2018

Wavefront errors of rotationally parabolic refractive X-ray lenses made of beryllium (Be CRLs) ha... more Wavefront errors of rotationally parabolic refractive X-ray lenses made of beryllium (Be CRLs) have been recovered for various lens sets and X-ray beam configurations. Due to manufacturingviaan embossing process, aberrations of individual lenses within the investigated ensemble are very similar. By deriving a mean single-lens deformation for the ensemble, aberrations of any arbitrary lens stack can be predicted from the ensemble with \bar{\sigma} = 0.034λ. Using these findings the expected focusing performance of current Be CRLs are modeled for relevant X-ray energies and bandwidths and it is shown that a correction of aberrations can be realised without prior lens characterization but simply based on the derived lens deformation. The performance of aberration-corrected Be CRLs is discussed and the applicability of aberration-correction demonstrated over wide X-ray energy ranges.

Journal of Instrumentation, 2018

The nature of retinal shielding pigment in the larval eyes of the midge Clunio marinus was studie... more The nature of retinal shielding pigment in the larval eyes of the midge Clunio marinus was studied by high resolution scanning X-ray fluorescence (XRF) analysis correlated with light microscopy (LM) and scanning coherent X-ray diffractive imaging (Ptychography). Clunio is known as a unique model system to decipher mechanisms underlying the complex moon-related rhythms. Shielding pigment granules within the photoreceptor cells of their primitive eyes (ocelli) have been shown to change appearance in the same rhythm. We compared the relative amount of trace metals (Ca, Ni, Zn, Cu), obtained by XRF, within single melanosomes (diameter about 500 nm) and the surrounding photoreceptor cells with their optical density in the light microscope and - for the first time - the electron density derived from the ptychography measurements. Though individual pigment granules can be identified and correlated in images of all three techniques the optical density, electron density and especially element concentrations within individual granules seem to vary independently. We discuss that the state of melanogenesis is not synchronized inside the ocellus

Microscopy and Microanalysis, 2018

Nature Communications, 2017

Due to their short wavelength, X-rays can in principle be focused down to a few nanometres and be... more Due to their short wavelength, X-rays can in principle be focused down to a few nanometres and below. At the same time, it is this short wavelength that puts stringent requirements on X-ray optics and their metrology. Both are limited by today's technology. In this work, we present accurate at wavelength measurements of residual aberrations of a refractive X-ray lens using ptychography to manufacture a corrective phase plate. Together with the fitted phase plate the optics shows diffraction-limited performance, generating a nearly Gaussian beam profile with a Strehl ratio above 0.8. This scheme can be applied to any other focusing optics, thus solving the X-ray optical problem at synchrotron radiation sources and X-ray freeelectron lasers.

Applied Physics Letters, 2017

Broadband optical absorption based on single-sized metal-dielectric-metal plasmonic nanostructure... more Broadband optical absorption based on single-sized metal-dielectric-metal plasmonic nanostructures with high-ε ″ metals Appl.

Advances in X-Ray/EUV Optics and Components XII, 2017

We developed a corrective phase plate that enables the correction of residual aberration in refle... more We developed a corrective phase plate that enables the correction of residual aberration in reflective, diffractive, and refractive X-ray optics. The principle is demonstrated on a stack of beryllium compound refractive lenses with a numerical aperture of 0.49 × 10 −3 at three different synchrotron radiation and x-ray free-electron laser facilities. By introducing this phase plate into the beam path, we were able to correct the spherical aberration of the optical system and improve the Strehl ratio of the optics from 0.29(7) to 0.87(5), creating a diffraction-limited, large aperture, nanofocusing optics that is radiation resistant and very compact.

The hard x-ray scanning microscope at beamline P06 of PETRA III at DESY in Hamburg serves a large... more The hard x-ray scanning microscope at beamline P06 of PETRA III at DESY in Hamburg serves a large user community, from physics, chemistry, and nanotechnology to the bio-medical, materials, environmental, and geosciences. It has been in user operation since 2012, and is mainly based on nanofocusing refractive x-ray lenses. Using refractive optics, nearly gaussian-limited nanobeams in the range from 50 to 100 nm can be generated in the hard x-ray energy range from 8 to 30 keV. The degree of coherence can be traded off against the flux in the nanobeam by a two-stage focusing scheme. We give a brief overview on published results from this instrument and describe its most important components and parameters.

Microscopy and Microanalysis, 2016

A new closed cell is presented forin situX-ray ptychography which allows studies under gas flow a... more A new closed cell is presented forin situX-ray ptychography which allows studies under gas flow and at elevated temperature. In order to gain complementary information by transmission and scanning electron microscopy, the cell makes use of a Protochips E-chipTMwhich contains a small, thin electron transparent window and allows heating. Two gold-based systems, 50 nm gold particles and nanoporous gold as a relevant catalyst sample, were used for studying the feasibility of the cell. Measurements showing a resolution around 40 nm have been achieved under a flow of synthetic air and during heating up to temperatures of 933 K. An elevated temperature exhibited little influence on image quality and resolution. With this study, the potential ofin situhard X-ray ptychography for investigating annealing processes of real catalyst samples is demonstrated. Furthermore, the possibility to use the same sample holder forex situelectron microscopy before and after thein situstudy underlines the un...

Applied Physics Letters, 2014

Advances in X-Ray/EUV Optics and Components VIII, 2013

Hard x-ray scanning microscopy relies on small and intensive nanobeams. Refractive x-ray lenses a... more Hard x-ray scanning microscopy relies on small and intensive nanobeams. Refractive x-ray lenses are well suited to generate hard x-ray beams with lateral dimensions of 100 nm and below. The diffraction limited beam size of refractive x-ray lenses mainly depends on the focal length and the attenuation inside the lens material. The numerical aperture of refractive lenses scales with the inverse square root of the focal length until it reaches the critical angle of total reflection. We have used nanofocusing refractive x-ray lenses made of silicon to focus hard x-rays at 8 and 20 keV to (sub-)100 nm dimensions. Using ptychographic scanning coherent diffraction imaging we have characterized these nanobeams with high accuracy and sensitivity, measuring the full complex wave field in the focus. This gives access to the full caustic and aberrations of the x-ray optics.

SPIE Proceedings, 2016

Due to the weak interaction of X-rays with matter and their small wavelength on the atomic scale,... more Due to the weak interaction of X-rays with matter and their small wavelength on the atomic scale, stringent requirements are put on X-ray optics manufacturing and metrology. As a result, these optics often suffer from aberrations. Until now, X-ray optics were mainly characterized by their focal spot size and efficiency. However, both measures provide only insufficient information about optics quality. Here, we present a quantitative analysis of residual aberrations in current beryllium compound refractive lenses using ptychography followed by a determination of the wavefront error and subsequent Zernike polynomial decomposition. Known from visible light optics, we show that these measures can provide an adequate tool to determine and compare the quality of various X-ray optics.