XDL2011 Workshop 5 Abstracts

Materials Science with Coherent Nanobeams at the Edge of Feasibility
Monday, June 27th - Tuesday, June 28th, 2011

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Organizers: Christian Riekel (European Synchrotron Radiation Facility), Simon Billinge (Columbia University), Kenneth Evans-Lutterodt (Brookhaven National Laboratory), & Detlef Smilgies (Cornell University)

Workshop Agenda (html)

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Introduction to ERL & Beamline Example: fluorescence analysis at the yoctogram level

Don Bilderback
Cornell University

ERLs and USRs are under consideration for next generation, high-duty cycle (>MHz rep rates), coherent x-rays sources. They both feature extremely high average spectral brightness, diffraction-limited performance and are the response to 3rd generation storage ring users/developers who would like "more x-ray flux, smaller x-ray beam size, more coherent x-ray flux on sample, higher energy resolution probes and/or short pulses for repetitive probing". In most cases, the x-ray beam should minimally impact the sample under study. We review the general features of ERLs and USRs in the context of the Cornell ERL and PEP-X as two well-developed examples from the x-ray community. Additionally, examples of utilization of the advanced properties of these machines will be given. The first example explores using the timing structure to repetitively probe the response of x-ray excited optical luminescence. The second uses the extremely high average brightness to conceptually develop ideas toward a confocal x-ray microscope that is designed to image single atoms based on either Thompson scattering or x-ray fluorescence.

Hard X-ray Scanning Nanoprobe: coherent nanobeam optics limits; refractive lenses

Christian G. Schroer
Technical University Dresden

With the high brilliance of ERL sources, x-ray microscopy and nanoanalysis can be pushed to well beyond the current capabilities. In addition, today's x-ray optics are mainly technology limited requiring further developments towards high optical quality and large numerical aperture. We review the x-ray optical capabilities of refractive x-ray lenses and discuss their potential for future improvements. Based on these optics the opportunities and limitations of x-ray microscopy at ERL sources is discussed, in particular those of coherent x-ray imaging techniques with the focused beam, such as ptychography.

3D and Atomic-resolution Imaging with Coherent Electron Nanobeams - Opportunities and Challenges for X-rays

David A. Muller
Cornell University

Atomic-resolution spectroscopic imaging in a new generation of electron microscopes is now capable of unraveling bonding details at buried interfaces and clusters, providing both physical and electronic structure information at the Angstrom-level. The sensitivity and resolution can extend to imaging single dopant atoms or vacancies in their native environments. The thousand-fold increase in electron energy loss spectroscopy (EELS) mapping speeds over conventional microscopes allows us to collect data from millions of spectra, generating statistically meaningful maps of heterogeneous populations - such as the facet-dependent leaching in fuel-cell catalysts nanoparticles. Tilt-series tomography allows us to record three-dimensional images with sub-nanometer resolution. Micro-machined environmental cells allow in-situ imaging of liquids and gases for samples ranging in thickness from nanometers to several microns. Current instruments under construction are expected to push spatial and energy resolution into the sub-Angstrom, milli-eV regime. Further developments are likely to enhance in-situ capabilities and detection schemes.

By mapping the evanescent electric field of the swift electron to a pulse of virtual photons, the different sensitivities of electrons and x-rays to elastic and inelastic scattering mechanisms and contrast can be compared, and optimal regimes for both methods can be identified. For instance, in radiation-sensitive samples, x-rays tend to be more efficient for inelastic spectroscopies and electrons are more efficient for elastic imaging.

High Resolution Hard X-ray Microscopy at the Advanced Photon Source: Current capabilities and Future thrust

Jörg Maser
Advanced Photon Source

Hard X-ray Microscopy has become a major characterization capability at the Advanced Photon Source, with applications ranging from biology and environmental science to nanoscience and materials science. We have recently developed and commissioned the first Hard X-ray Nanoprobe (HXN), which is operated in partnership between the Advanced Photon Source and Argonne's Center for Nanoscale Materials. The HXN allows characterization of structure, strain and composition of advanced materials and devices using nanoscale diffraction and x-ray fluorescence. In addition, the HXN integrates a tomographic full-field transmission mode that is used to characterize the 3-dimensional structure of complex systems and devices. By taking advantage of high accuracy position sensing, we are also able to exploit ptychography in diffraction mode to study structure of subregions of novel thin film materials with a resolution below the spot size of currently 40 nm. We will discuss applications of this multimodal tool to the study of advanced materials and devices.

To carry hard x-ray microscopy into the range of length scales below 10 nm, we have developed novel x-ray optics, dubbed multilayer Laue lenses (MLL). These optics have demonstrated a one-dimensional resolution of 16 nm and a focusing efficiency of 30% for hard x-rays in the past [2]. We have recently demonstrated a 2D spatial resolution of well below 30 nm, and efficiencies as high as 17% for photon energies between 10 and 20 keV.

In applying our advanced focusing and nanopositioning techniques to questions in energy science, materials science and environmental science, we are now developing, in the context of the APS upgrade, a next-generation nanoprobe beamline, the In-Situ Nanoprobe (INP). The INP will be optimized for X-ray fluorescence, provide variable temperature capabilities ranging from 100 K to 1000°C, and allow application of external fields as well as flow of gases. Using advanced mirror optics, this system will provide a spatial resolution of 50 nm with three orders of magnitude more flux than nanoprobes based on diffractive optics, and use multilayer Laue lenses to achieve a resolution of 20 or below. We will present the scientific thrust of the INP and discuss our conceptual design.

The Degradation Mechanisms of Matisse's and van Gogh's Pigments - Probing Photo-oxidation Reactions at the Nanoscale

Jennifer Mass
University of Delaware

The synthetic inorganic pigments in the turn of the 20th century masterpieces of Impressionist and early modern art are undergoing degradation phenomena ranging from fading and color shifts to catastrophic failure. Recent studies of zinc yellow (K₂O.4ZnCrO₄.3H₂O), chrome yellow (PbCrO ₄), and cadmium yellow (CdS) have identified the alteration products and preliminary mechanisms for paint layer failure. However, comprehensive degradation mechanisms that will allow specific environmental requirements for display remain elusive. Photo-induced degradation is a surface phenomenon, often occurring in only the top 1-5 microns of the paint layer, and the photodegradation products are minor phases within this alteration layer. The preservation of the icons of early modern art hinges on the spatially-resolved atomic and molecular characterization of these minute heterogeneous alteration layers, an analytical challenge requiring chemical imaging with at least nanogram sensitivity. New rapid, high resolution, and highly sensitive chemical imaging tools for the inorganic and organic components of the disfiguring degradation layers are needed. μXANES with a 1-2 µm beam is the SR-based method that is currently used to probe these alteration layers. However, to preserve these icons of early modern art for future generations, it is critical that we identify incipient photodegradation, chemical evidence of photodegradation prior to any change in the painting's appearance. Incipient photodegradation occurs in the top 1-2 microns of the paint layer, and so increased resolution is required to study the composition of this layer as a function of depth. NanoXANES is anticipated to be of great utility for these systems. Other SR-based methods that have potential for the characterization of these alteration layers are nanoXRD, nanoXRF, PEEM, and confocal µXRF. The chemical imaging methods developed must also be rapid to permit screening of representative paint cross-sections from important early modern art collections such as those at MOMA, The Barnes Foundation, The Metropolitan Museum of Art, and the Art Institute of Chicago.

Fluorescence Tomography in a Diamond Anvil Cell

Wendy Mao
Stanford University

Nanoscale x-ray computed tomography (nanoXCT) within a laser-heated diamond anvil cell has exciting potential as a powerful 3D probe for non-destructive, nanoscale (<40nm) resolution of multiple crystalline and amorphous phases which are synthesized under extreme conditions. The ability to tune the incident energy range allows access elemental edges for near edge scans to map coordination, oxidation states, and spin states, and provide quantitative composition information within the sample. Results from high pressure-temperature experiments which illustrate the potential for this technique will be presented.

3D X-ray Fluorescence Tomography with Nanoscale Resolution on Cosmic Dust

Laszlo Vincze
Ghent University

X-ray fluorescence tomography and polycapillary based confocal XRF imaging using synchrotron radiation are among the most sensitive, non-destructive microanalytical methods providing three-dimensional (3D), potentially quantitative information on the elemental distributions in the probed sample volume with trace-level detection limits.

These XRF imaging methods have been applied at submicron resolution levels for the non-destructive 2D/3D elemental analysis of unique cometary micro-particles which were sampled and brought to Earth in the framework of NASA's Stardust mission. These unique micro-particles, which were captured in aerogel, have been examined by a large number of research groups during the preliminary examination period using various non-destructive microanalytical techniques^1,2.

The examined aerogel samples typically contained a single elongated cavity (called track) produced by the impact of a single comet coma particle. We performed multiple experiments on such tracks and their terminal particles at the ESRF beamline ID13 using 2D and 3D nano X-ray fluorescence (XRF) and scanning X-ray diffraction. The nanobeam of X-rays was produced by a linear Bragg-Fresnel lens or a KB-mirror system, reducing the beam dimensions to 170-300 nm level.

Our measurements provided the first fully three-dimensional, trace-level elemental information with submicron spatial resolution from some of these unique extraterrestrial materials³. Next to presenting the currently applied methodology, the future potential of these techniques will be discussed with respect to the upcoming new generation of SR sources.

References:

1. D. Brownlee et al., Science 314, 1711 (2006)
2. G. Flynn et al., Science 314, 1731 (2006)
3. G. Silversmit et al., Analytical Chemistry 81, 6107 (2009)

X-ray Fluorescence Microscopy for Biology and Bionanotechnology: Challenges and Unique Opportunities

Stefan Vogt
Advanced Photon Source

Hard x-ray fluorescence microscopy is a powerful technique to map and quantify element distributions in biological specimens such as cells and bacteria. It provides attogram sensitivity for transition metals like Cu, Zn, and other biologically relevant trace elements. It is perfectly placed to map nanoparticles and nanovectors within cells, at high spatial resolution. Making use of tomographic approaches, in combination with the capability to penetrate whole cells, 3D elemental distribution can be acquired and visualized. Phase contrast allows one to sensitively detect cell ultrastructure, and combine structural information of the sample with trace elemental content.

Ever faster detectors, better optics, and improved data acquisition strategies provide great opportunities that could be fully exploited with significantly improved x-ray source characteristics. We will summarize state of the art X-ray fluorescence microscopy, identify existing challenges, and speculate on future opportunities and unique applications in the area of the life sciences.

In-situ Probing of Fuel Cell and Battery Systems

Héctor Abruña
Cornell University

This presentation will deal with the use of x-ray based methods, with emphasis on diffraction and XAS, for the in-situ study of materials for applications in fuel cells and battery systems. Emphasis will be placed on ordered intermetallics as anodes for fuel cells and organosulfur materials and elemental sulfur for battery cathodes. Preliminary studies on metal oxides and germanium nanowires will also be discussed

Adventures in Microcrystallography of Biological Specimens

David Eisenberg
University of California, Los Angeles

With the goal of advancing methods of crystallography for applications to the energy and health sciences, we have been exploring the potential of structure elucidation with specimens that are at least 10,000 times smaller than conventional biological samples. In 2005, we were able to report the atomic structures of two microcrystals containing untwisted amyloid-like fibrils, giving the first glimpse of the atomic arrangement of proteins in the amyloid state. Both structures were short, fibril-forming segments of the yeast prion protein, Sup35, which itself forms amyloid-like fibrils. The microcrystals were of the order of 2 µm in cross section. Diffraction data were collected on ESRF beamline ID13, equipped with a MAR CCD detector. Since then, we have determined structures for some 90 other amyloid-like microcystals, with X-ray diffraction data collected at ESRF, SLS, and APS.

In recent work, we have found that informative X-ray diffraction patterns can be recorded from even smaller microcrystals and even from biological cells and subcellular granules containing ordered protein. This work was carried out at ESRF beamlline ID13 and Spring 8. The significance of this preliminary work is three fold. First it demonstrates that subcellular organelles can contain protein in highly ordered states. Second, it suggests that in vivo structure determination is feasible. Third, it suggests that X-ray structure determination of nanometer or micrometer-scale biological crystals may become routine, for cases in which only minute amounts of protein are available, or for which only micrometer scale ordered samples can be prepared. This development would accelerate research both in bioenergy sciences and health sciences.

Research support from: DOE BER, HHMI, NIH, Keck Foundation and NSF.

GISAXS: Development and Applications using Nanobeams, Microbeams and Tomography

Stephan V. Roth
Deutsches Elektronen-Synchrotron

Nanocomposite thin films play an ever increasing role in modern information and energy science. This is owing to their outstanding physical properties, being an effect of the confinement of the electrons in the nanoscopic structure. To tailor these functional films, a multitude of deposition methods is used. To name just a few are solution casting [1,2] or sputter deposition [3,4]. To obtain the structure-function relationship a multitude of methods is applied. On the one hand, structural information on the nanometer to micrometer scale is obtained using grazing incidence small- and wide-angle x-ray scattering [5]. Especially the the combination of micro- and nanobeams and special techniques such as (GI)SAXS-tomography allow for spatially resolved investigations of heterogeneous structures on multiple length scales [6,7,8]. On the other hand, to obtain the structure-function relationship, the in-situ combination with complementary methods is very useful. This includes the novel combination with imaging ellipsometry or microfluidic setups [9]. I will present the state-of-the art of the different combinations by specific research examples and will give an outlook on future trends in these areas.

References:

1. S.V. Roth, A. Rothkirch, T. Autenrieth, R. Gehrke, T. Wroblewski, M.C. Burghammer, C. Riekel, L. Schulz, R. Hengstler, and P. Müller-Buschbaum; Langmuir, 26, 1496 (2010)
2. S.V. Roth, T. Autenrieth, G. Grübel, C. Riekel, M. Burghammer, R. Hengstler, L. Schulz, and P. Müller-Buschbaum; Appl. Phys. Lett. 91, 091915 (2007)
3. A. Buffet, M.M. Abul Kashem, K. Schlage, S. Couet, R. Röhlsberger, A. Rothkirch, G. Herzog, E. Metwalli, R. Meier, G. Kaune, M. Rawolle, P. Müller-Buschbaum, R. Gehrke, and S.V. Roth; Langmuir 27, 343 (2011)
4. S.V. Roth, H. Walter, M. Burghammer, C. Riekel, B. Lengeler, C. Schroer, M. Kuhlmann, T. Walther, A. Sehrbrock, R. Domnick, ans P. Müller-Buschbaum; Appl. Phys. Lett. 88, 021910 (2006)
5. J. Perlich, J. Rubeck, S. Botta, R. Gehrke, S.V. Roth, M.A. Ruderer, S.M. Prams, M. Rawolle, Q. Zhong, V. Körstgens, and P. Müller-Buschbaum; Rev. Sci. Instr. 81, 105105 (2010)
6. C.G. Schroer, M. Kuhlmann, S.V. Roth, R. Gehrke, N. Stribeck, A. Almendarez-Camarillo, and B. Lengeler; Appl. Phys. Lett. 88, 164102 (2006)
7. M. Kuhlmann, J.M. Feldkamp, J. Patommel, S.V. Roth, A. Timmann, R. Gehrke, Peter Müller-Buschbaum, and C.G. Schroer; Langmuir 25, 7241 (2009)
8. S.V. Roth, G. Herzog, V. Körstgens, A Buffet, M. Schwartzkopf, J. Perlich, M.M. Abul Kashem, R. Döhrmann, R. Gehrke, A. Rothkirch, K. Stassig, W. Wurth, G. Benecke, C. Li, P. Fratzl, M. Rawolle, and P. Müller-Buschbaum; J. Phys: Cond. Matter, accepted (2011)
9. E. Metwalli, J.-F. Moulin, J. Perlich, W. Wang, A. Diethert, S.V. Roth, and P. Müller-Buschbaum; Langmuir 25, 11815 (2009)

Contact-free Manipulation and Probing of Single Biological and Soft Matter Objects

Christian Riekel
European Synchrotron Radiation Facility

The extent to which nanometer-sized X-ray beams will find practical applications depends on the availability of advanced sample environments and manipulation tools. Pushing the limits to smaller X-ray beams and objects will require the integration of more and more nanotechnology in a synchrotron radiation experiment. I will discuss in my talk techniques for deposition, manipulation and probing of fragile biological and soft matter objects involving low contact forces which have recently been explored. Examples are optical tweezers, inkjet systems and superhydrophobic surfaces. The experiments discussed are performed in situ and usually in an aqueous environment which is particular interest for studying biological processes such as biomineralization. The examples will also be used to discuss some challenges for next generation experiments involving brilliant nanobeams.

X-ray Detectors: State-of-the-art & Future Possibilities

Sol Gruner
Cornell University

The state-of-the-art of quantitative imaging x-ray detectors is described. We then consider upcoming technologies that may be applied to imaging detectors to advance the state-of-the-art with respect to pixel size and functionality, spatial resolution, time resolution, analog dynamic range, and energy resolution. Specifically, we look into our crystal ball and ask what is likely feasible on a decade time scale, given adequate R&D, given current physical limits of materials and technology.

Ultrafast Diffraction with Nanobeams: reversible and irreversible processes

Paul Evans
University of Wisconsin, Madison

The future development of high-repetition-rate ultrafast x-ray sources with a high degree of coherence will enable the creation of new nanobeam probes with a unique combination of spatial resolution, time resolution, and structural precision. These probes have the potential provide insight that is not available with present techniques. This talk will highlight examples from applications in which dynamics at the picosecond timescale and at nanometer length-scales are crucial, but are only beginning to be understood.

The first of these areas addresses the need to understand the evolution of mesoscopic order in condensed systems. Emerging degrees of freedom, including novel ferroelectric domain geometries and charge ordering, have fascinating and potentially useful dynamical properties. It is already possible in some cases to probe the dynamics of an ensemble of these 10-nm-scale structures using synchrotron-based techniques but it is not yet possible to obtain dynamical information about phase transitions and defects at the single-domain scale. We will illustrate the opportunities in this area with the specific example of striped polarization domains in a ferroelectric/dielectric PbTiO ₃/SrTiO₃ superlattice (Figure 1).

A second exciting opportunity arises from the need to probe materials driven into transient non-equilibrium structural states by large applied electric fields. Large fields have the potential to fundamentally alter the structure of complex oxides, and promise to provide a means to control electronic, magnetic, and electromechanical properties. At present, x-ray based probes provide excellent static structural precision but often lack either the spatial or time resolution (or both!) required to study small volumes of material, often in thin films or nanostructures, driven far from equilibrium.

Figure 1: Time-evolution of a diffuse x-ray refection from striped polarization domains in a PbTiO3 /SrTiO3 ferroelectric dielectric superlattice. The decrease in the intensity of the satellite reflection (at left) arises from the switching of the system into a single-domain state beginning at t=0.

High-Energy Scattering with Micro- and Nanobeams

Harald Reichert
European Synchrotron Radiation Source

Rapid progress in X-ray optics allows now to produce tailored high energy micro- and nanobeams routinely. The prospect of new low-emittance sources such as an Energy Recovery Linacs or an Ultimate Storage Ring on the horizon brightens this picture considerably. Extrapolating the parameter, it is apparent that these beams are ideally suited for in-situ and in-operando materials science applications. This builds in particular on one of the defining features of high energy X-ray beams: the capacity to penetrate complex sample environments for access to deeply buried structures. Combined with the capacity to achieve time resolution down into the picosecond domain with high repetition rates we expect to gain insight into materials and materials processing with unprecedented resolution. Examples of experiments not possible today should stimulate a discussion to build the scientific case for such a resource.

3D Ptychography with Differential Aperture Microscopy

Gene Ice
Oakridge National Laboratory

The development of differential aperture microscopy provides a powerful tool for mapping local crystal structure with submicron three-dimensional (3D) resolution. This tool has wide applications for understanding the distribution and evolution of elastic strain and plastic deformation in materials. We are now exploring the possibility of extending these methods into the coherent regime. Here the differential aperture is itself a perturbation of the diffraction pattern from the sample and new reconstruction methods will be needed that treat the absorbing wire much like an imperfect probe beam in current coherent diffraction methods. In this talk we will outline the instrumentation needed to perform such experiments, describe our limited attempts to test the suitability of existing instruments and present a path forward toward exploring these methods. If successful, this approach will enable nm-scale studies on volumes deep inside materials, which are clearly impossible by any other means.

This research is funded by the Center for Defect Physics, an Energy Frontier Research Center of the Office of Science, Office of Basic Energy Science, U. S. Department of Energy.

Nanostructure and Diffraction of Heterogeneous Materials with Nanobeams

Simon Billinge
Columbia University

The next generation of synchrotron based sources will have unique performance characteristics with extremely low emittance and high brightness like a linac based source, combined with high rep-rates and high time-integrated fluxes. In this talk we will explore what some of the scientific frontiers and challenges are in materials science and structure determination of complex materials and how they may benefit from these source characteristics. In particular, one of the major challenges is the complexity of materials that are being explored next generation technological solutions. These contain many elements, contain defects that are critical to the properties and are structured at the nanoscale. They are generally manufactured into complicated heterogeneous devices with sub-micron sized features and as functioning materials change over time as the device functions. We therefore need tools that can carry out time-resolved measurements with accurately positioned nano-dimensioned beams that can probe an operating device (and therefore penetrate any packaging or special environment) in a non-destructive way to extract quantitative structural information. Because of the complexity of structural solutions it will often be necessary to have complementary data from more than one method and software that can handle the heterogeneous data in a coherent modeling scheme, something we are calling Complex Modeling. The aim of the talk will be to stimulate discussion about scientific needs and scattering based technological solutions made feasible at a next generation ERL or USR.

Coherent Diffraction Imaging with Nano- and Microbeams

Mark Pfeifer
Cornell University

Coherent diffraction imaging (CDI) is a promising x-ray microscopy technique because it does not require a lens for image formation, so its resolution is not tied to precision of optics fabrication. The resolution is dictated by wavelength, detector geometry, signal-to-noise, and ultimately radiation damage. CDI can still take advantage of focusing optics to provide improved flux on the sample, to provide an illumination which is finite in extent (useful in the ptychography variant of CDI), and provides a strong phase structure. This last aspect can be used to improve the convergence of CDI analysis routines in Fresnel CDI.

While CDI is usually thought of as requiring a coherent, planar wave incident upon the sample, a more general treatment simply requires that the complex wave field of the illumination be well characterized. CDI methods can computationally recover the wave field in any plane, including the focal plane, from an image of the intensity in the far field of the focus, provided there is sufficient coherence in the wave field. The fractional coherence of a beam is unchanged by focusing, but providing coherent illumination moderate sized optics with hard x-rays at third generation sources is impractical- hence the need for high brilliance, high fractional coherence future sources. An ideal CDI microscope would scan a highly focused beam, at each scan point recording an x-ray fluorescence spectrum, photoelectron yield, and a coherent diffraction pattern. Three dimensional information would be obtained tomographically or by scanning the lens to sample distance.