Significant developments in micro-electrical-mechanical systems (MEMS)-based devices for use in transmission electron microscopy (TEM) sample holders have recently led to the commercialization of windowed gas cells that now enable the atomic-resolution visualization of phenomena occurring during gas-solid interactions at atmospheric pressure. In situ atmospheric TEM study provides unique information that is beneficial to correlating the structure-properties relationship of catalytic nanomaterials, particularly under realistic gaseous reaction conditions. In this paper, we illustrate the capability of this novel in situ device as applied to our study of two catalyst systems: (1) In situ kinetic growth of free standing Pt nanowires as active catalysts toward oxygen reduction reaction (ORR); (2) In situ observation of facet-dependent oxidation of another promising ORR catalyst, Pt3Co nanoparticles.

Chip-package interaction (CPI) and the related thermomechanical stress in microchips increase the risk of failure in on-chip interconnect stacks, caused by delamination along Cu/dielectrics interfaces (adhesive failure) and fracture in dielectrics (cohesive failure). High-resolution transmission X-ray microscopy (TXM) is a unique technique to image crack propagation in on-chip interconnect stacks. The visualization of crack evolution in Cu/low-k Backend-of-Line (BEoL) structures is demonstrated using an experimental setup which combines high-resolution X-ray imaging with mechanical loading. The application of an indenter manipulator at the TXM beamline of the synchrotron radiation source BESSY II provides an unprecedented level of details on the fracture behavior of microchips. This in-situ experiment allows to identify the weakest layers and interfaces and to evaluate the robustness of the BEoL stack against CPI.

Liquid crystal polymers (LCP’s) comprise a class of materials that derive desirable, but anisotropic, engineering properties from long-range molecular ordering. The ability to model the polymer texture is essential to the design of manufacturing processes for isotropic material production. Previous efforts to model LCP directionality have been primarily restricted to structured grids and simple geometries that demonstrate the underlying theory, but fall short of simulating realistic manufacturing geometries. In this investigation, a practical methodology is proposed to simulate the director field in full-scale melt-processing domains and wide-angle x-ray scattering (WAXS) is used to experimentally validate modeling results. It is shown that the model generates good agreement with experimental measurements of both the orientation state and degree of order.

We report on the results of coherent X-ray diffraction imaging (CXDI) and ptychography measurements of two individual core-shell-shell GaAs/(In,Ga)As/GaAs nanowires (NWs) grown by molecular beam epitaxy (MBE) on patterned Si(111) substrate. CXDI at the axial GaAs 111 Bragg reflection was applied at different positions along the NW axis in order to characterize the NWs in terms of structural homogeneity along the radial directions. At each positon 3D reciprocal space maps have been recoded and inverted using phase retrieval algorithms. The CXDI were complemented by 2D ptychography measurements at GaAs 111 Bragg reflection probing the same NWs with respect to their structural homogeneity. Both methods provide structural homogeneity for NW1 and NW2 except at the bottom part of the NWs. In case of NW2 CXDI and ptychography show changes in the structure of the top part of the NW indicated by 60° rotation of the indicated three-fold rotational symmetry in the observed diffraction patterns and changes in the strain field reconstructed from ptychography.

The purpose of this research work is to gain a better understanding of the nanostructural properties of Molybdenum (Mo) thin films’ porosity, nanovoid heterogeneity and provide detailed quantitative data on voids volume fractions, sizes, shapes, and their preferred orientations as the growth sputtering pressure changes systematically. This knowledge shall assists in optimizing Mo film nano- and micro-structural properties as desired for solar cells applications. Therefore, two separate series of Mo thin films (∼ 0.7 μm thick) were deposited on high purity (99.999) Al-foil (10 μm thick), and Si/SiO2 substrates using direct-current (DC) planar magnetron sputtering. The sputtering pressure was varied from 0.8 mT to 12 mT, with a sputtering power density of 1.2 W/cm2. High-Resolution Scanning Electron Microscopy (HRSEM) was used to examine the Mo films’ morphology. Whereas, the Mo films’ bulk resistivity was calculated from the films’ thickness and average sheet resistance measurements using Dektak Surface Profilometer, and Four Point Probe method, respectively. Small Angle X-Ray Scattering (SAXS) technique was applied to examine the existence of nanovoids and its heterogeneity in the Mo-coated Al foils (Al/Mo). Moreover, the porosity of the Mo films as a function of sputtering pressure was studied by Transmission Electron Microscopy (TEM) on Mo-coated Si/SiO2 (Si/SiO2/Mo) substrates.

Plasticity in as-grown gold nanowires deformed in three-point bending configuration was studied by Laue microdiffraction. One-dimensional orientation maps of the Au crystal along the nanowire were generated from which the deformation profile was inferred. The crystal lattice was found to rotate continuously around the Au $[\bar{2}11]$ direction, which is transverse to the wire axis evidencing the storage of geometrically necessary dislocations (GNDs). The analysis of the diffraction peak shape points to the activation of multiple slip systems in contrast to the formation of wedge shaped twins predicted by MD simulations.

Three dimensional X-ray diffraction (3DXRD) microscopy is a powerful technique that provides crystallographic and spatial information of a large number, of the order of thousands, of crystalline grains in a sample simultaneously. A key component of every 3DXRD microscopy experiment is the near field detector that provides high resolution spatial information of the grains. In this work we present a novel design for a semi-transparent, 16 megapixel near field detector. As opposed to a typical single scintillator phosphor detector, this design, we call the Quad Near Field Detector, uses four quadrants. It has a total field of view is 5.3 mm x 5.3 mm with an effective pixel size of 1.3 µm x 1.3 µm. The detector’s relatively large field of view can be used to obtain higher order diffraction spots which we anticipate will lead to improved spatial resolution in grain reconstructions. The large field of view can also enable the detector to be positioned further from the sample, in this way increasing the working distance and enabling larger environmental cells for in-situ studies. Many alignment parameters can be resolved by careful mechanical design. For this reason a novel translation stage for focusing the microscopes was developed, tested, and implemented. The near field detector was calibrated and characterized at the Cornell High Energy Synchrotron Source. The operational feasibility of such a multi-plate detector demonstrated in this work paves the way for new technologies in instrumentation of 3DXRD microscopy.

Second-order diffraction (SOD) of x-rays refers to all diffraction processes where the photons reaching the detector have been diffracted twice within a crystal lattice. By measuring the two dimensional intensity profile of SOD, it is possible to distinguishing rescattering processes taking place inside each grain (perfect crystal domain) or in between grains. These two SOD regimes, usually called dynamical and kinematical, respectively, are ruled by size and relative orientation of the grains. In this work, we demonstrate how to explore SOD phenomena to understand the micro scale grain structure in plastically deformed silicon single crystal.

The structural descriptions of even the most basic amorphous materials are under considerable debate. In this work, an intuitive computational technique has been developed to construct 3D statistical density maps to directly visualize and identify local atomic structures from simple monatomic amorphous germanium (a-Ge) to complex multi-atom systems such as copper zirconium metallic glass. We show motifs in copper zirconium that are unresolvable through traditional tools such as Voronoi indexing. This self-sorted local atomic motif (SLAM) method builds upon the Kabsch algorithm incorporating techniques in computer vision to produce least-squares optimized 3D density maps. Simultaneously, the SLAM method incorporates self-contained categorization to define local motifs based upon atomic structures. We present the methodology of the SLAM method and also present resulting motifs comparing models a-Ge and demonstrate its broad capability on metallic glass.