Characterization of sub-monolayer coatings as novel calibration samples for X-ray spectroscopy

With the advent of both modern X-ray fluorescence (XRF) methods and improved analytical reliability requirements the demand for suitable reference samples has increased. Especially in nanotechnology with the very low areal mass depositions, quantification becomes considerably more difficult. However, the availability of suited reference samples is drastically lower than the demand. Physical vapor deposition (PVD) techniques have been enhanced significantly in the last decade driven by the need for extremely precise film parameters in multilayer production. We have applied those techniques for the development of layer-like reference samples with mass depositions in the ng-range and well below. Several types of reference samples were fabricated: multi-elemental layer and extremely low (sub-monolayer) samples for various applications in XRF and total-reflection XRF (TXRF) analysis. Those samples were characterized and compared at three different synchrotron radiation beamlines at the BESSY II electron storage ring employing the reference-free XRF approach based on physically calibrated instrumentation. In addition, the homogeneity of the multi-elemental coatings was checked at the P04 beamline at DESY. The measurements demonstrate the high precision achieved in the manufacturing process as well as the versatility of application fields for the presented reference samples

Preparation of clay mineral samples for high resolution x-ray imaging

In the development of optimum ceramic materials for plastic forming, it is of fundamental importance to gain insight into the compositions of the clay minerals. Whereas spectroscopic methods are adequate for determining the elemental composition of a given sample, a knowledge of the spatial composition, together with the shape and size of the particles leads to further, valuable insight. This requires an imaging technique such as high resolution X-ray microscopy. In addition, fluorescence spectroscopy provides a viable element mapping technique. Since the fine particle fraction of the materials has a major effect on physical properties like plasticity, the analysis is focused mainly on the smallest particles. To separate these from the bigger agglomerates, the raw material has to pass through several procedures like centrifugation and filtering. After that, one has to deposit a layer of appropriate thickness on to a suitable substrate. These preparative techniques are described here, starting from the clay mineral raw materials and proceeding through to samples that are ready to analyze. First results using high resolution x-ray imaging are shown

A phase retrieval algorithm based on three-dimensionally translated diffraction patterns55 S.)

An iterative phase retrieval method is proposed that combines alternating projections and registration of three-dimensionally translated near-field diffraction patterns. This method allows to enhance resolution limited by a finite detector size and automatically stitches the assembled data while avoiding the need for a priori knowledge or scanning of the object as encountered in coherent diffraction imaging or ptychography

Target materials for efficient plasma-based extreme ultraviolet sources in the range of 6 to 8 nm

In a comparative study the extreme ultraviolet (XUV) emission of laser-produced plasmas(LPP) of gadolinium (Gd), terbium (Tb), aluminum (Al), magnesium (Mg) and a magnesium–copper–gadolinium alloy (Mg65–Cu25–Gd10) targets is investigated in order to benchmark the emission potential at a wavelength of around 6.7 nm. Compared to the Gd/Tb targets, the advantage of the alloy is a reduced melting point of Tm < 500 °C which leads to the option of a liquid or droplet target system as is usually used for a regenerative target concept. Theoretical considerations are presented to compare the emission potential of the four targets in direct comparison. Experimental results of the LPP are discussed with respect to the 6.x nm inband energy, which are consistent with the theoretical considerations. It is shown that the line radiators Al and Mg seem to be suitable emitters with comparable brightness to Gd- or Tb-based sources. The measured conversion efficiency of the Mg65Cu25Gd10 target reaches80% of that of the pure Gd LPP although the Gd fraction is only 2% (atom percent)

Preparation of clay mineral samples for high resolution x-ray imaging

In the development of optimum ceramic materials for plastic forming, it is of fundamental importance to gain insight into the compositions of the clay minerals. Whereas spectroscopic methods are adequate for determining the elemental composition of a given sample, a knowledge of the spatial composition, together with the shape and size of the particles leads to further, valuable insight. This requires an imaging technique such as high resolution X-ray microscopy. In addition, fluorescence spectroscopy provides a viable element mapping technique. Since the fine particle fraction of the materials has a major effect on physical properties like plasticity, the analysis is focused mainly on the smallest particles. To separate these from the bigger agglomerates, the raw material has to pass through several procedures like centrifugation and filtering. After that, one has to deposit a layer of appropriate thickness on to a suitable substrate. These preparative techniques are described here, starting from the clay mineral raw materials and proceeding through to samples that are ready to analyze. First results using high resolution x-ray imaging are shown

Data compression strategies for ptychographic diffraction imaging

Ptychography is a computational imaging method for solving inverse scattering problems. To date, the high amount of redundancy present in ptychographic data sets requires computer memory that is orders of magnitude larger than the retrieved information. Here, we propose and compare data compression strategies that significantly reduce the amount of data required for wavefield inversion. Information metrics are used to measure the amount of data redundancy present in ptychographic data. Experimental results demonstrate the technique to be memory efficient and stable in the presence of systematic errors such as partial coherence and noise

Time-resolved imaging of domain pattern destruction and recovery via nonequilibrium magnetization states

The destruction and formation of equilibrium multidomain patterns in permalloy (Ni80Fe20) microsquares has been captured using pump-probe x-ray magnetic circular dichroism (XMCD) spectromicroscopy at a new full-field magnetic transmission soft x-ray microscopy endstation with subnanosecond time resolution. The movie sequences show the dynamic magnetization response to intense Oersted field pulses of approximately 200-ps root mean square (rms) duration and the magnetization reorganization to the ground-state domain configuration. The measurements display how a vortex flux-closure magnetization distribution emerges out of a nonequilibrium uniform single-domain state. During the destruction of the initial vortex pattern, we have traced the motion of the central vortex core that is ejected out of the microsquare at high velocities exceeding 1 km/s. A reproducible recovery into a defined final vortex state with stable chirality and polarity could be achieved. Using an additional external bias field, the transient reversal of the square magnetization direction could be monitored and consistently reproduced by micromagnetic simulations

Scanning transmission X-ray microscopy with efficient X-ray fluorescence detection (STXM-XRF) for biomedical applications in the soft and tender energy range

Scanning transmission X-ray microscopy, especially in combination with X-ray fluorescence detection (STXM-XRF) in the soft X-ray energy range, is becoming an increasingly important tool for life sciences. Using X-ray fluorescence detection, the study of biochemical mechanisms becomes accessible. As biological matrices generally have a low fluorescence yield and thus a low fluorescence signal, high detector efficiency (e.g. large solid angle) is indispensable for avoiding long measurement times and radiation damage. Here, the new AnImaX STXM-XRF microscope equipped with a large solid angle of detection enabling fast scans and the first proof-of-principle measurements on biomedical samples are described. In addition, characterization measurements for future quantitative elemental imaging are presented