Nanofocus X-ray Diffraction Research Articles

Formation and structure of ZIF-8@PEO coating on the surface of zinc

Recently, plasma electrolytic oxidation (PEO) found broad application as a multi-purpose process to create effective corrosion and wear resistant coatings on various metallic substrates. The exceptional properties of metal organic frameworks (MOFs) put them also in focus as perspective materials for corrosion protection. In this work, the formation of a novel ZIF-8@PEO coating is reported for the first time. It was synthesized by controllable recrystallization of a PEO layer formed on zinc alloy Z1 into ZIF-8 in the presence of 2-methylimidazole organic linkers. The multi-stage mechanism of PEO to ZIF-8 rearrangement is proposed. Cross section, glow discharge optical emission spectroscopy and nano-focused synchrotron X-ray diffraction demonstrated that varying of synthesis parameters, the ZIF-8@PEO coating with different distribution of ZIF-8 through PEO layer can be prepared. Based on the results of laser scanning microscopy, the surface smoothing was observed with increasing the degree of the PEO-to-ZIF-8 rearrangement. Containing two components, the novel ZIF-8@PEO coating is expected to combine admirable physical-chemical properties of both PEO and ZIF-8. Such a feature can open the way for its potential application not only for corrosion protection, but also for photo- and heterogeneous catalysis.

Assessing Fast Structure Formation Processes in Isotactic Polypropylene with a Combination of Nanofocus X-ray Diffraction and In Situ Nanocalorimetry.

A combination of in situ nanocalorimetry with simultaneous nanofocus 2D Wide-Angle X-ray Scattering (WAXS) was used to study polymorphic behaviour and structure formation in a single micro-drop of isotactic polypropylene (iPP) with defined thermal history. We were able to generate, detect, and characterize a number of different iPP morphologies using our custom-built ultrafast chip-based nanocalorimetry instrument designed for use with the European Synchrotron Radiation Facility (ESRF) high intensity nanofocus X-ray beamline facility. The detected iPP morphologies included monoclinic alpha-phase crystals, mesophase, and mixed morphologies with different mesophase/crystalline compositional ratios. Monoclinic crystals formed from the mesophase became unstable at heating rates above 40 K s−1 and showed melting temperatures as low as ~30 K below those measured for iPP crystals formed by slow cooling. We also studied the real-time melt crystallization of nanogram-sized iPP samples. Our analysis revealed a mesophase nucleation time of around 1 s and the co-existence of mesophase and growing disordered crystals at high supercooling ≤328 K. The further increase of the iPP crystallization temperature to 338 K changed nucleation from homogeneous to heterogeneous. No mesophase was detected above 348 K. Low supercooling (≥378 K) led to the continuous growth of the alpha-phase crystals. In conclusion, we have, for the first time, measured the mesophase nucleation time of supercooled iPP melted under isothermal crystallization conditions using a dedicated experimental setup designed to allow simultaneous ultrafast chip-based nanocalorimetry and nanofocus X-ray diffraction analyses. We also provided experimental evidence that upon heating, the mesophase converts directly into thermodynamically stable monoclinic alpha-phase crystals via perfection and reorganization and not via partial melting. The complex phase behaviour of iPP and its dependence on both crystallization temperature and time is presented here using a time–temperature–transformation (TTT) diagram.

Epitaxy in Polybutene-1 Form II-on-Form I Cross-Nucleation Revealed by Nanofocused X-ray Diffraction on Ad Hoc Morphology

Epitaxy in Polybutene-1 Form II-on-Form I Cross-Nucleation Revealed by Nanofocused X-ray Diffraction on Ad Hoc Morphology

Inducing ferroelastic domains in single-crystal CsPbBr3 perovskite nanowires using atomic force microscopy

Understanding and controlling the formation and dynamics of ferroelastic domains can be key to enhance metal halide perovskite device performance, but established methods lack spatial control at the level of single domains. Here, the authors induced the formation of ferroelastic domains in CsPbBr${}_{3}$ nanowires using an atomic force microscope tip, and studied the structural changes using nanofocused x-ray diffraction with a 60-nm beam. The applied stress locally induced lattice tilts that define room temperature-stable ferroelastic domains, which spread spatially and terminated at {112}-type domain walls. While pristine regions show an orthorhombic (004) reflection; regions exposed to higher forces exhibit {220}-type reflections.

Hierarchical architecture of spider attachment setae reconstructed from scanning nanofocus X-ray diffraction data.

When sitting and walking, the feet of wandering spiders reversibly attach to many surfaces without the use of gluey secretions. Responsible for the spiders' dry adhesion are the hairy attachment pads that are built of specially shaped cuticular hairs (setae) equipped with approximately 1 µm wide and 20 nm thick plate-like contact elements (spatulae) facing the substrate. Using synchrotron-based scanning nanofocus X-ray diffraction methods, combining wide-angle X-ray diffraction/scattering and small-angle X-ray scattering, allowed substantial quantitative information to be gained about the structure and materials of these fibrous adhesive structures with 200 nm resolution. The fibre diffraction patterns showed the crystalline chitin chains oriented along the long axis of the attachment setae and increased intensity of the chitin signal dorsally within the seta shaft. The small-angle scattering signals clearly indicated an angular shift by approximately 80° of the microtrich structures that branch off the bulk hair shaft and end as the adhesive contact elements in the tip region of the seta. The results reveal the specific structural arrangement and distribution of the chitin fibres within the attachment hair's cuticle preventing material failure by tensile reinforcement and proper distribution of stresses that arise upon attachment and detachment.

Ferroelectric monoclinic phases in strained K0.70Na0.30NbO3 thin films promoting selective surface acoustic wave propagation

We present a detailed analysis of the ferroelectric domain structure of K0.70Na0.30NbO3 thin films on (110) TbScO3 grown by metal–organic chemical vapor deposition. Upon piezoresponse force microscopy and nanofocus x-ray diffraction measurements we derive a domain model revealing monoclinic MC domains. The complex domain pattern is formed out of four co-existing in-plane orientations of the shearing direction of the monoclinic unit cell resulting in four types of superdomains each being composed of well-ordered stripe domains. Finally, we present surface acoustic wave (SAW) experiments that exhibit extraordinary signal intensities given the low thickness of the tested film. Moreover, the SAW propagation is found to occur selectively along the identified shearing directions.

Reactor for nano-focused x-ray diffraction and imaging under catalytic in situ conditions.

A reactor cell for in situ studies of individual catalyst nanoparticles or surfaces by nano-focused (coherent) x-ray diffraction has been developed. Catalytic reactions can be studied in flow mode in a pressure range of 10-2-103 mbar and temperatures up to 900 °C. This instrument bridges the pressure and materials gap at the same time within one experimental setup. It allows us to probe in situ the structure (e.g., shape, size, strain, faceting, composition, and defects) of individual nanoparticles using a nano-focused x-ray beam. Here, the setup was used to observe strain and facet evolution of individual model Pt catalysts during in situ experiments. It can be used for heating other (non-catalytically active) nanoparticles (e.g., nanowires) in inert or reactive gas atmospheres or vacuum as well.

Bending and Twisting Lattice Tilt in Strained Core-Shell Nanowires Revealed by Nanofocused X-ray Diffraction.

We have investigated strained GaAs-GaInP core-shell nanowires using transmission electron microscopy and nanofocused scanning X-ray diffraction. Nominally identical growth conditions for each sample were achieved by using nanoimprint lithography to create wafer-scale arrays of Au seed particles. However, we observe large individual differences, with neighboring nanowires showing either straight, bent, or twisted morphology. Using scanning X-ray diffraction, we reconstructed and quantified the bending and twisting of the nanowires in three dimensions. In one nanowire, we find that the shell lattice is tilted with respect to the core lattice, with an angle that increases from 2° at the base to 5° at the top. Furthermore, the azimuthal orientation of the tilt changes by 30° along the nanowire axis. Our results demonstrate how strained core-shell nanowire growth can lead to a rich interplay of composition, lattice mismatch, bending and lattice tilt, with additional degrees of complexity compared with thin films.

Structure and Composition of Isolated Core-Shell(In,Ga)N/GaNRods Based on Nanofocus X-Ray Diffraction and Scanning Transmission Electron Microscopy

Nanofocus x-ray diffraction is used to investigate the structure and local strain field of an isolated ðIn; GaÞN=GaN core-shell microrod. Because the high spatial resolution of the x-ray beam is only 80 × 90 nm2, we are able to investigate several distinct volumes on one individual side facet. Here, we find a drastic increase in thickness of the outer GaN shell along the rod height. Additionally, we performed highangle annular dark-field scanning-transmission-electron-microscopy measurements on several rods from the same sample showing that (In,Ga)N double-quantum-well and GaN barrier thicknesses also increase strongly along the height. Moreover, plastic relaxation is observed in the top part of the rod. Based on the experimentally obtained structural parameters, we simulate the strain-induced deformation using the finiteelement method, which serves as the input for subsequent kinematic scattering simulations. The simulations reveal a significant increase of elastic in-plane relaxation along the rod height. However, at a certain height, the occurrence of plastic relaxation yields a decrease of the elastic strain. Because of the experimentally obtained structural input for the finite-element simulations, we can exclude unknown structural influences on the strain distribution, and we are able to translate the elastic relaxation into an indium concentration which increases by a factor of 4 from the bottom to the height where plastic relaxation occurs.

Nanofocus x-ray diffraction and cathodoluminescence investigations into individual core–shell (In,Ga)N/GaN rod light-emitting diodes

Employing nanofocus x-ray diffraction, we investigate the local strain field induced by a five-fold (In,Ga)N multi-quantum well embedded into a GaN micro-rod in core–shell geometry. Due to an x-ray beam width of only 150 nm in diameter, we are able to distinguish between individual m-facets and to detect a significant in-plane strain gradient along the rod height. This gradient translates to a red-shift in the emitted wavelength revealed by spatially resolved cathodoluminescence measurements. We interpret the result in terms of numerically derived in-plane strain using the finite element method and subsequent kinematic scattering simulations which show that the driving parameter for this effect is an increasing indium content towards the rod tip.

Counterintuitive strain distribution in axial (In,Ga)N/GaN nanowires

We study the three-dimensional deformation field induced by an axial (In,Ga)N segment in a GaN nanowire. Using the finite element method within the framework of linear elasticity theory, we study the dependence of the strain field on the ratio of segment length and nanowire radius. Contrary to intuition, the out-of-plane-component εzz of the elastic strain tensor is found to assume large negative values for a length-to-radius ratio close to one. We show that this unexpected effect is a direct consequence of the deformation of the nanowire at the free sidewalls and the associated large shear strain components. Simulated reciprocal space maps of a single (In,Ga)N/GaN nanowire demonstrate that nanofocus x-ray diffraction is a suitable technique to assess this peculiar strain state experimentally.

Нанокалориметрия высокого временного разрешения и ее сочетание с микро- и нанофокусной рентгеновской дифракцией для исследования функциональных наноструктурированных материалов

Нанокалориметрия высокого временного разрешения и ее сочетание с микро- и нанофокусной рентгеновской дифракцией для исследования функциональных наноструктурированных материалов

Smart Energetic Nanosized Co-Crystals: Exploring Fast Structure Formation and Decomposition

The interest in co-crystals of energetic materials is explained by the fact that they can offer better thermodynamic stability and tunable sensitivity and detonation performance. In the present work, a combination of DSC, ultrafast chip calorimetry, high-resolution X-ray powder diffraction, and nanofocus X-ray diffraction was employed to investigate the thermal behavior and structure formation in nanosized co-crystals of CL-20 with HMX and TNT prepared using Spray Flash Evaporation (SFE). The CL-20/HMX co-crystal does not reveal any thermal transitions up to the thermal decomposition. In contrast, CL-20/TNT exhibits an irreversible melting transition. Upon melting, it can rapidly crystallize on heating or, at a slower pace, at room temperature to form homocrystals of γCL-20, the polymorph stable at high temperature. These observations constitute the first evidence of a CL-20 crystallization process, which occurs from the melt and not from solution. The solid–liquid phase separation occurring during heatin...

Strain accommodation through facet matching in La1.85Sr0.15CuO4/Nd1.85Ce0.15CuO4 ramp-edge junctions

Scanning nano-focused X-ray diffraction and high-angle annular dark-field scanning transmission electron microscopy are used to investigate the crystal structure of ramp-edge junctions between superconducting electron-doped Nd1.85Ce0.15CuO4 and superconducting hole-doped La1.85Sr0.15CuO4 thin films, the latter being the top layer. On the ramp, a new growth mode of La1.85Sr0.15CuO4 with a 3.3° tilt of the c-axis is found. We explain the tilt by developing a strain accommodation model that relies on facet matching, dictated by the ramp angle, indicating that a coherent domain boundary is formed at the interface. The possible implications of this growth mode for the creation of artificial domains in morphotropic materials are discussed.

Efficient modeling of Bragg coherent x-ray nanobeam diffraction.

X-ray Bragg diffraction experiments that utilize tightly focused coherent beams produce complicated Bragg diffraction patterns that depend on scattering geometry, characteristics of the sample, and properties of the x-ray focusing optic. Here, we use a Fourier-transform-based method of modeling the 2D intensity distribution of a Bragg peak and apply it to the case of thin films illuminated with a Fresnel zone plate in three different Bragg scattering geometries. The calculations agree well with experimental coherent diffraction patterns, demonstrating that nanodiffraction patterns can be modeled at nonsymmetric Bragg conditions with this approach--a capability critical for advancing nanofocused x-ray diffraction microscopy.

X-ray diffraction strain analysis of a single axial InAs 1-x Px nanowire segment.

The spatial strain distribution in and around a single axial InAs 1-x Px hetero-segment in an InAs nanowire was analyzed using nano-focused X-ray diffraction. In connection with finite-element-method simulations a detailed quantitative picture of the nanowire's inhomogeneous strain state was achieved. This allows for a detailed understanding of how the variation of the nanowire's and hetero-segment's dimensions affect the strain in its core region and in the region close to the nanowire's side facets. Moreover, ensemble-averaging high-resolution diffraction experiments were used to determine statistical information on the distribution of wurtzite and zinc-blende crystal polytypes in the nanowires.

Switching Chirality of Hybrid Left–Right Crystalline Helicoids Built of Achiral Polymer Chains: When Right to Left Becomes Left to Right

It is widely accepted that achiral polymers crystallize in lamella helicoids of both handedness, whereas chiral polymers are known to form helicoids of only one handedness. By employing nanofocus X-ray diffraction, we show that the situation is more complex and that the lamella helicoids of achiral polymers can be in fact hybrid, i.e., containing a left- and a right-handed part. Moreover, our data demonstrate that the poly(trimethylene terephthalate) lamellae invert chirality at a certain crystallization temperature. The chirality correlates with the growth axis polarity (i.e., a versus −a) and handedness of the lamellar helicoid (L versus R) and can be conveniently expressed in terms of the chirality parameter pairs. In addition, the overall chain tilt does not affect the rate and sense of twisting, calling into question the premise of the Keith and Padden model. Instead, the inclination of the terminal segment of the crystalline stem protruding the lamellar surface is proposed to be the key factor contr...

Scanning force microscope for in situ nanofocused X-ray diffraction studies.

A compact scanning force microscope has been developed for in situ combination with nanofocused X-ray diffraction techniques at third-generation synchrotron beamlines. Its capabilities are demonstrated on Au nano-islands grown on a sapphire substrate. The new in situ device allows for in situ imaging the sample topography and the crystallinity by recording simultaneously an atomic force microscope (AFM) image and a scanning X-ray diffraction map of the same area. Moreover, a selected Au island can be mechanically deformed using the AFM tip while monitoring the deformation of the atomic lattice by nanofocused X-ray diffraction. This in situ approach gives access to the mechanical behavior of nanomaterials.

Local magnetization and strain in single magnetoelectric microrod composites

Magneto-optic Kerr effect microscopy and nanofocus X-ray diffraction are combined to investigate the local mapping of the magnetoelectric microcomposite properties of ZnO microrods coated with an amorphous (Fe90Co10)78Si12B10 layer. We follow the magnetic domain behavior and lattice deformation upon applying an external magnetic field. In addition to the expected field induced strain, we observe a local magnetic induced strain in the 10−5 range in the ZnO localized near the (Fe90Co10)78Si12B10 /ZnO interface.

Hard X-ray imaging of bacterial cells: nano-diffraction and ptychographic reconstruction

Ptychographic coherent X-ray diffractive imaging (PCDI) has been combined with nano-focus X-ray diffraction to study the structure and density distribution of unstained and unsliced bacterial cells, using a hard X-ray beam of 6.2keV photon energy, focused to about 90nm by a Fresnel zone plate lens. While PCDI provides images of the bacteria with quantitative contrast in real space with a resolution well below the beam size at the sample, spatially resolved small angle X-ray scattering using the same Fresnel zone plate (cellular nano-diffraction) provides structural information at highest resolution in reciprocal space up to 2nm(-1). We show how the real and reciprocal space approach can be used synergistically on the same sample and with the same setup. In addition, we present 3D hard X-ray imaging of unstained bacterial cells by a combination of ptychography and tomography.