/pdf/microfracturing-and-microporosity-in-shales-v3zxb9oxq1.pdf

Microfracturing and microporosity in shales

Advances in microscopy techniques based on x-rays have opened unprecedented opportunities in terms of spatial resolution, combined with chemical and morphology sensitivity, to analyze solid, soft and liquid matter. The advent of ultrabright third and fourth generation photon sources and the continuous development of x-ray optics and detectors has pushed the limits of imaging and spectroscopic analysis to structures as small as a few tens of nanometers. Specific interactions of x-rays with matter provide elemental and chemical sensitivity that have made x-ray spectromicroscopy techniques a very attractive tool, complementary to other microscopies, for characterization in all actual research fields. The x-ray penetration power meets the demand to examine samples too thick for electron microscopes implementing 3D imaging and recently also 4D imaging which adds time resolution as well. Implementation of a variety of phase contrast techniques enhances the structural sensitivity, especially for the hard x-ray regime. Implementation of lensless or diffraction imaging helps to enhance the lateral resolution of x-ray imaging to the wavelength dependent diffraction limit.

/pdf/transmission-and-emission-x-ray-microscopy-operation-modes-49bl9xyamn.pdf

Transmission and emission x-ray microscopy: operation modes, contrast mechanisms and applications.

This review discusses recent progress in the development of hard X-ray microscopy techniques for materials characterization at the nanoscale. Although the utility of traditionally ensemble-based X-ray techniques in materials research has been widely recognized, the utility of X-ray techniques as a tool for local characterization of nanoscale materials properties has undergone rapid development in recent years. Owing to a confluence of improvements in synchrotron source brightness, focusing optics fabrication, detection, and data analysis, nanoscale X-ray imaging techniques have moved beyond proof-of-principle experiments to play a central role in synchrotron user programs worldwide with high-impact applications made to materials science questions. Here, we review the current state of synchrotron-based, hard X-ray nanoscale microscopy techniques—including 3D tomographic visualization, spectroscopic elemental and chemical mapping, microdiffraction-based structural analysis, and coherent methods for nanomate...

Nanoscale Hard X-Ray Microscopy Methods for Materials Studies*

Hard X-ray fluorescence microscopy is one of the most sensitive techniques for performing trace elemental analysis of biological samples such as whole cells and tissues. Conventional sample preparation methods usually involve dehydration, which removes cellular water and may consequently cause structural collapse, or invasive processes such as embedding. Radiation-induced artifacts may also become an issue, particularly as the spatial resolution increases beyond the sub-micrometer scale. To allow imaging under hydrated conditions, close to the `natural state', as well as to reduce structural radiation damage, the Bionanoprobe (BNP) has been developed, a hard X-ray fluorescence nanoprobe with cryogenic sample environment and cryo transfer capabilities, dedicated to studying trace elements in frozen-hydrated biological systems. The BNP is installed at an undulator beamline at sector 21 of the Advanced Photon Source. It provides a spatial resolution of 30 nm for two-dimensional fluorescence imaging. In this first demonstration the instrument design and motion control principles are described, the instrument performance is quantified, and the first results obtained with the BNP on frozen-hydrated whole cells are reported.

/pdf/the-bionanoprobe-hard-x-ray-fluorescence-nanoprobe-with-a3zy564dle.pdf

The Bionanoprobe: hard X-ray fluorescence nanoprobe with cryogenic capabilities.

The development of high brightness X-ray sources and high resolution X-ray optics has led to rapid advances in X-ray microscopy. Scanning microscopes and full-field instruments are in operation at synchrotron light sources worldwide, and provide spatial resolution routinely in the 25–50 nm range using zone plate focusing elements. X-ray microscopes can provide elemental maps and/or chemical sensitivity in samples that are too thick for electron microscopy. Lensless techniques, such as diffraction microscopy, holography and ptychography are also being developed. In high resolution imaging of radiation-sensitive material the effects of radiation damage needs to be carefully considered. This article is designed to provide an introduction to the current state and future prospects of X-ray microscopy for the non-expert.

New directions in X-ray microscopy

We describe the new full-field transmission x-ray microscope (TXM) for automated cryo-tomography and nano-spectroscopy which is installed at the BESSY undulator U41. For the first time in soft x-ray microscopy, an elliptically shaped single-bounce glass capillary is employed as condenser which collects the divergent radiation emerging from the exit slit of a focusing spherical grating monochromator (FSGM). The new TXM overcomes several limitations of conventional TXM setups, it provides an energy resolution up to E/ΔE = 104 which is well suited for spectromicroscopy. Furthermore, no pinhole is required close to the sample plane which facilitates flat sample holder geometry for nano-tomography. With its high energy resolution, the TXM also supports imaging in high orders of diffraction of the zone plate objective. Using this approach, a spatial resolution of 14 nm lines and spaces is demonstrated. In addition, we present selected applications from materials and life sciences.

Energy-tunable full-field x-ray microscopy: Cryo-tomography and nano-spectroscopy with the new BESSY TXM

Fresnel zone plates are the key optical elements for soft and hard x-ray microscopy. For short exposure times and minimum radiation load of the specimen the diffraction efficiency of the zone plate objectives has to be maximized. As the efficiency strongly depends on the height of the diffracting zone structures the achievable aspect ratio of the nanostructures determines these limits. To reach aspect ratios ≥ 20:1 for high efficient optics we propose to superimpose zone plates on top of each other. With this multiplication approach the final aspect ratio is only limited by the number of stacked zone plate layers. For the stack process several nanostructuring process steps have to be developed and/or improved. Our results show for the first time two layers of zone plates stacked on top of each other.

Towards stacked zone plates

The Helmholtz‐Zentrum Berlin (HZB) operates a transmission x‐ray microscope (TXM) in the soft x‐ray photon energy range with an energy resolution up to E/ΔE = 104 [1]. An approach to achieve ultrahigh spatial resolution with conventional, standard zone plate optics is to employ higher orders of diffraction of the zone plate objective [2]. In this paper, we demonstrate that 11‐nm lines and spaces of a multilayer test structure are clearly resolved by the x‐ray microscope using the third order of diffraction of a zone plate objective with 20‐nm outermost zone width. The disadvantage of high‐order imaging is an about one order of magnitude lower diffraction efficiency of the used zone plates employed in the third order compared to the first order of diffraction. In addition, the measured background signal in the TXM images is no longer negligible. Therefore, we worked on the fabrication of zone plates with sub‐20‐nm outermost zone width to increase the spatial resolution in the first order of diffraction. A ...

Soft X‐Ray Microscopy at HZB: Zone Plate Development and Imaging Using the Third Order of Diffraction

The full-field transmission X-ray microscope at the electron storage ring BESSY II allows nanoscale spectroscopy as well as correlative fluorescence and nanoscale tomographic imaging of frozen-hydrated adherent cells. Reconstructions of tilt series permit the visualization of the sub-cellular structures in mammalian cells and plant cells. Quantitative information about package densities of cell organelles in the cytoplasm is possible. We present an overview of recent results in materials and life sciences obtained with the HZB X-ray microscope.

https://iopscience.iop.org/article/10.1088/1742-6596/463/1/012032/pdf

Nanoscale spectroscopy and tomography with the HZB X-ray microscope: Applications in materials and life sciences

X‐rays have the advantage that they penetrate samples which are several micrometers thick without significant sample damage, and that they provide a chemical image contrast between different dielectric layers of the Cu/low‐k on‐chip interconnect stack. Therefore, x‐ray microscopy is an ideal tool for quantitative 3‐D investigations of void dynamics with high spatial resolution of 20 nm. Using the BESSY full‐field transmission x‐ray microscope (TXM), we performed electromigration studies of advanced backend‐of‐line (BEoL) stacks of high‐performance microprocessors containing copper interconnects and low‐k materials. We observed void movement along the top copper/dielectric (SiNx) interface which is found to be the main pathway for electromigration‐induced atomic copper transport.

G. Schneider

Papers

Energy-tunable full-field x-ray microscopy: Cryo-tomography and nano-spectroscopy with the new BESSY TXM

Towards stacked zone plates

Soft X‐Ray Microscopy at HZB: Zone Plate Development and Imaging Using the Third Order of Diffraction

Nanoscale spectroscopy and tomography with the HZB X-ray microscope: Applications in materials and life sciences

X-ray Microscopy Studies of Electromigration in Advanced Copper Interconnects