Characterization of Materials through High Resolution Coherent Imaging: Coherent Imaging II
Sponsored by: TMS Structural Materials Division, TMS: Advanced Characterization, Testing, and Simulation Committee
Program Organizers: Ross Harder, Argonne National Lab; Xianghui Xiao, Argonne National Laboratory; Richard Sandberg, Los Alamos National Laboratory; Saryu Fensin, Los Alamos National Laboratory; Brian Abbey, LaTrobe University; Ana Diaz, Paul Scherrer Institut

Monday 2:00 PM
February 27, 2017
Room: 25B
Location: San Diego Convention Ctr

Session Chair: Xiaojing Huang, Brookhaven National Laboratory

2:00 PM  
Coherent X-ray Diffraction Measurements of Lattice Distortions Caused by Ion Bombardment: Felix Hofmann1; Edmund Tarleton1; Ross Harder2; Nicholas Phillips3; Jesse Clark4; Ian Robinson5; Brian Abbey3; Wenjun Liu2; Yevhen Zayachuk1; Christian Beck1; 1University of Oxford; 2Argonne National Lab; 3LaTrobe University; 4SLAC National Accelerator Laboratory; 5University College
    Focussed Ion Beam (FIB) milling is a mainstay of nano-scale machining. Using a tightly focussed ion beam, often gallium (Ga+), FIB can sculpt nanostructures via localised sputtering. This ability to cut solid matter on the nano-scale revolutionised sample preparation across the life-, earth- and materials sciences. However, despite its widespread usage, detailed understanding of the functional consequences of FIB-induced damage, intrinsic to the technique, remains elusive. Here, we study the nano-scale strain fields brought about by FIB-exposure of initially pristine gold nano-crystals. Using Bragg Coherent Diffraction Imaging (BCDI), we measure the full, 3D-resolved lattice strain tensor within each nano-crystal. Even low gallium ion doses, typical of FIB imaging, cause substantial lattice distortions. At higher doses extended self-organised defect structures appear. Combined with detailed numerical calculations, these observations provide fundamental insight into the nature of the damage created, and the structural instabilities that lead to a surprisingly inhomogeneous morphology.

2:30 PM  
Unraveling the Structure-function Relationships in Ion Implanted Nanodiamonds: Salman Maqbool1; Alastair Stacey2; Nicholas Phillips1; Henry Kirkwood1; Brett Johnson2; Ross Harder3; David Hoxley1; Brian Abbey1; 1La Trobe University; 2The University of Melbourne; 3Advanced Photon Source
    The unique set of chemical, optical, electronic, and mechanical properties of nanodiamonds (NDs) make them suitable for a wide range of applications including drug delivery and quantum computing. These useful properties of nanodiamonds can be tuned through modification of their surface chemistry and internal structure. A particularly important example of this is the optoelectronic characteristic behavior of nanodiamonds incorporating nitrogen-vacancy (N-V) defect centres. N-V centre nanodiamonds exhibit extraordinary photoluminescence and quantum-sensing properties, and are also being used as cellular biomarkers. In spite of the huge interest in these samples however, there is still a substantial gap in our knowledge of how their structural properties, particularly in the near-surface region, influence their function. Here we present results from a study, using a combination of Optically Detected Magnetic Resonance (ODMR) spectroscopy, fluorescence mapping as well as Bragg Coherent Diffractive Imaging (BCDI), that aims to unravel the structure-function properties of N-V centre nanodiamonds.

3:00 PM  
Imaging Strain Fields by Ptychographic Topography: Steven Van Petegem1; Ana Diaz1; Maxime Dupraz1; Ainara Irastorza1; 1Paul Scherrer Institut
    X-ray topography is a well-established method to visualize dislocations and associated strain fields in single crystals. It is based on Bragg diffraction and provides a two-dimensional intensity mapping of the diffracted beam. The resolution is typically limited by the pixel size of the detector, which restricts its practical usage to relatively large objects and defects. In this work we present a new method, ptychographic topography, where we combine tele-ptychography (H.R. Tsai et al. Optics Express 24 (2016) 6441) and Bragg topography. In tele-ptychography an object is illuminated with a parallel x-ray beam and the wave front after propagation through the object is reconstructed using an analyzer downstream the sample. In combination with Bragg topography it allows obtaining high-resolution topographs and in contrast to conventional topography it additionally provides phase contrast. We apply this method to visualize the strain field around an indent in a thin Si wafer.

3:20 PM Break

3:40 PM  
Progress towards Dichroic Bragg Coherent Diffractive Imaging: Jonathan Logan1; Ross Harder1; Luxi Li1; Daniel Haskel1; Daniel Rosenmann1; Martin Holt1; Yihua Liu1; Tenzin Sangpo1; Robert Winarski1; Ian McNulty1; 1Argonne National Laboratory
    Magnetization is coupled to the atomic lattice strain in crystals by the magnetoelastic energy. X-ray diffraction methods are powerful tools for study of magnetism and lattice strain, however there are currently no tools for measuring these properties simultaneously at the nanoscale, where local strain fields can influence magnetic domain configurations. By combining x-ray magnetic circular dichroism and Bragg coherent diffractive imaging methods, it should be possible to image nanoscale strain and magnetization at the same time, with a single measurement. We are developing dichroic BCDI techniques for imaging strain and magnetization simultaneously, in two and three dimensions, in isolated magnetic nanocrystals and magnetic thin films. We use circularly polarized x-rays produced by a diamond x-ray phase retarder to gain sensitivity to magnetism. To quantify the feasibility of these methods we are testing them with novel magnetic material systems such as faceted Cobalt-Platinum nanocrystals and tungsten-encapsulated Gadolinium nanocrystals.

4:10 PM  
Photoelastic Ptychography: A New Approach for Quantitative Stress Determination: Guido Cadenazzi1; Keith Nugent1; Nicholas Anthony1; Brian Abbey1; 1La Trobe University
    We present an experimental study of the elastic properties of materials explored through photoelastic ptychography. This work is an extension of a recent simulation study by Ferrand et al (Opt. Lett. 40, 5144-5147 (2015)). The circular polariscope in combination with holographic photoelasticity allows the sum and difference of principal stress components to be determined. Phase stepping and interferometric techniques have been proposed as a method for separating the in-plane stress components in two-dimensional photoelasticity experiments. Here we describe a new experimental approach to the problem of quantifying stress and birefringence in transparent samples based on photoelastic ptychography. The quantitative birefringent information provides a direct window into the samples’ mechanical properties which can then be used, e.g. for predictive modelling. We have validated our results against a well-studied engineering problem, the diametrically compressed disc. The analysis of this sample as well as several others of biological significance will be discussed.

4:30 PM  
Soft-X-ray Ptychographic Imaging of Shale: Namhey Lee1; Peter Nico1; David Shapiro1; Manika Prasad2; Timothy Kneafsey1; Benjamin Gilbert1; 1Lawrence Berkeley National Lab; 2Colorado School of Mines
    Shales are important sedimentary rock formations for energy resources and geologic storage of waste materials due to their very low permeability. Soft-X-ray ptychography provides a new approach for imaging the pore structures in shale that is complementary to electron microscopy, helium ion microscopy and scanning transmission X-ray microscopy. Ptychography acquires the complex refractive index of the sample that is better suited to low-density materials such as kerogen. We performed non-resonant soft-X-ray ptychographic imaging of carbonate rich (Niobara) and organic rich (Bakken) shale rocks thinned to 0.5 Ám using focused ion beam milling. In all samples, two-dimensional (2D) projection images revealed complex internal structure with 5-nm features resolved. In organic-rich shale, 2D transmission images reveal nanoscale porosity consistent with HIM images of fractured shale. Wavy lamellar structures within organic components are likely clay minerals. However, determination of nanoscale pore structure is affected by statistical noise in the diffraction data.

4:50 PM  
Polychromatic Bragg Coherent X-ray Diffraction Imaging for Rapid Measurements: Wonsuk Cha1; Stephan Hruszkewycz1; Matthew Highland1; Ross Harder1; Wenjun Liu1; Ruqing Xu1; Paul Fuoss1; 1Argonne National Laboratory
    Coherent x-ray diffraction imaging (CDI) performed in Bragg geometry has been employed as a powerful technique to examine three-dimensional strain distributions within nanocrystals. However the current state-of-art of CDI requires significant time to perform three-dimensional scans making it incompatible with most time-resolved studies. In this talk, I will discuss a new approach for CDI with the goal of obtaining three-dimensional coherent x-ray diffraction patterns without scanning samples. Polychromatic coherent x-ray delivered by third-generation synchrotron sources allows transient diffraction patterns collected during phase transition of the sample within short time. It also makes CDI on complex heterogeneous crystalline materials simplified with a two stage, screening and imaging process. This innovative approach may provide opportunities for time-resolved Bragg CDI studies.

5:10 PM  
Coherent X-ray Imaging at Future High Brightness Synchrotron Sources: Ross Harder1; 1Argonne National Laboratory
    Several synchrotron radiation facilities around the world are developing plans to increase the brightness of the sources by factors of 100. This will elevate coherent x-ray diffractive imaging to a new level of capability. It is anticipated that atomic resolution could be achieved in some samples. This talk will describe some properties of the new sources that will enable entirely new science and introduce state of the art imaging instrumentation that is being planned for these new sources.