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Electronic or catalytic properties can be modified at the nanoscale level. Engineering efficient and specific nanomaterials requires the ability to study their complex structure–property relationships. Here, Bragg coherent diffraction imaging was used to measure the three‐dimensional shape and strain of platinum nanoparticles with a diameter smaller than 30 nm, i.e. significantly smaller than any previous study. This was made possible by the realization of the Extremely Brilliant Source of ESRF, The European Synchrotron. This work demonstrates the feasibility of imaging the complex structure of very small particles in three dimensions and paves the way towards the observation of realistic catalytic particles. [ABSTRACT FROM AUTHOR]

The observation of atomic ordering and signatures of defects in self-assembled Ge islands using x-ray diffraction techniques have been previously treated as unrelated subjects. However, mutual understanding can be achieved when both subjects are studied in a common frame. Here, we report on measurements and analysis of both defects and atomic ordering in Si1-xGex islands epitaxially grown on Si(001) substrates as a function of growth temperature. By using x-ray diffraction and mapping around a bulk forbidden reflection, defect sizes, and in-plane spacing between nearby dislocations are extracted and related to the composition of the islands. The results fit well with an independent determination using selective wet chemical etching and atomic force microscopy measurements. Moreover, the temperature dependence of the ordered domain size is discussed. Although both atomic ordering and defect formation take place independently in the system, it is found that the relaxation provided by the onset of defects does not affect the formation of ordered domains, recently pointed out to be stabilized by strain and surface equilibrium on islands facets. [ABSTRACT FROM AUTHOR]

Highlights • Composition of SiGe domes grown on vicinal Si(0 0 1) substrates were studied. • Synchrotron resonant x-ray diffraction measurements (Ge K-edge). • Elastic energy in islands grown on miscut substrates obtained for different Ge content. • Finite Elements Simulation points out that elastic energy is stored on new facets. Abstract We investigate here the influence of Si substrate miscut on the strain and elastic energy of Ge islands. We show how the morphology, composition and the elastic energy for 4 and 13 monolayers (ML) Ge islands grown at 600 °C and 730 °C on vicinal Si(0 0 1) surfaces change with miscut angles ranging between 0° and 10°. Scanning Tunneling Microscopy is used to determine the island morphology. Resonant x-ray diffraction near the Ge-K absorption edge allows the determination of the Ge concentration as well as the elastic energy stored on such structures from their dependency on the lattice parameter. Simulations using the Finite Elements Method indicate that the enlargement of the SiGe broad peak retrieved from the x-ray diffraction measurements is actually caused by the asymmetrical faceting induced by large miscut angles. Such faceting has a strong effect on island density and elastic energy, producing differences that are proportional to those observed in conditions with distinct SiGe content. [ABSTRACT FROM AUTHOR]

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 setupwas 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. [ABSTRACT FROM AUTHOR]

Phase change materials (PCMs) such as Ge 2 Sb 2 Te 5 (GST) undergo a reversible amorphous-to-crystal transition that is the basis of their interest for next generation non-volatile memories. The large density change upon crystallization raises important issues because of the large mechanical stresses occurring during memory cycling. In order to investigate the intimate relationship between stress buildup and microstructure evolution we have built a dedicated setup, which allows combining X-ray diffraction and curvature measurements on DiffAbs beamline at SOLEIL synchrotron. Using a thin (30 nm) GST film deposited on Si we show that this setup yields a wealth of interesting results. A clear correlation is observed between phase transition and stress buildup. Detailed information is obtained on the thermomechanical behavior of the different phases. Systematic investigation of PCMs with this original setup will help understanding the thermomechanical behavior of PCM thin films and nanostructures. [ABSTRACT FROM AUTHOR]

Texture evolution is an important issue in materials and nanosciences. Understanding it is fundamental for controlling the final orientation, which in fine controls the desired properties of nanodevices. Here, we reveal the formation of a peculiar texture during the silicidation of nanoscale Pd thin films. We demonstrate that the crystallographic relationship observed between the silicide and the Si(001) substrate, named gyroaxy, evolves continuously and collectively during silicidation. This continuous rotation of the nanosized grains over a wide angular range is proposed to be associated with a diffusional mechanism [ABSTRACT FROM AUTHOR]

Semiconductor heteroepitaxy on top of thin compliant layers has been explored as a path to make inorganic electronics mechanically flexible as well as to integrate materials that cannot be grown directly on rigid substrates. Here, we show direct evidences of strain transfer for InAs islands on freestanding Si thin films (7 nm). Synchrotron X-ray diffraction measurements using a beam size of 300 x 700 nm² can directly probe the strain status of the compliant substrate underneath deposited islands. Using a recently developed diffraction mapping technique, three-dimensional reciprocal space maps were reconstructed around the Si (004) peak for specific illuminated positions of the sample. The strain retrieved was analyzed using continuous elasticity theory via Finite-element simulations. The comparison of experiment and simulations yields the amount of strain from the InAs islands, which is transferred to the compliant Si thin film. [ABSTRACT FROM AUTHOR]

Strain in silicon induced by Through-Silicon Via (TSV) integration is of particular interest in the frame of the integration of active devices in silicon interposer. Nano-focused X-ray beam diffraction experiments were conducted using synchrotron radiation to investigate the thermally induced strain field in silicon around copper filled TSVs. Measurements were performed on thinned samples at room temperature and during in situ annealing at 400°C. In order to correlate the 2D strain maps with finite elements analysis, an analytical model was developed, which takes into account beam absorption in the sample for a given diffraction geometry. The strain field along the [335] direction is found to be in the 10-5 range at room temperature and around 10-4 at 400°C. Simulations support the expected plastification in some regions of the TSV during the annealing step. [ABSTRACT FROM AUTHOR]

Compositional atomic ordering is a crucial issue in the epitaxial growth of nanoparticles and thin films. Here, we report on a method based on x-ray diffuse scattering close to basis forbidden Bragg reflections to infer the lateral location, the symmetry, and the thermal stability of ordered domains in GeSi dome-shaped islands on Si(001) after growth and during annealing. We observe that atomic ordering does not disappear after annealing, demonstrating that it is a resilient metastable phenomenon. [ABSTRACT FROM AUTHOR]

Compositional atomic ordering is a crucial issue in the epitaxial growth of nanoparticles and thin films. Here, we report on a method based on x-ray diffuse scattering close to basis forbidden Bragg reflections to infer the lateral location, the symmetry, and the thermal stability of ordered domains in GeSi dome-shaped islands on Si(001) after growth and during annealing. We observe that atomic ordering does not disappear after annealing, demonstrating that it is a resilient metastable phenomenon. [ABSTRACT FROM AUTHOR]

Abstract: Palladium–silicon (Pd–Si) is a model system for investigating stress development during solid state reaction because of the formation of one single phase (hexagonal Pd2Si). In this work we have measured simultaneously the curvature of the substrate and the diffracted signal from the films during reactive diffusion of a thin Pd (25nm) film with a Si(001) substrate. Only the diffracted signal was measured during the solid state reaction of Pd(25nm) with Si(111). The combined experiment allows monitoring in situ stress and strain during the growth of Pd2Si. The combination method also permits the determination of the elastic constants and thermal expansion coefficient of Pd2Si assuming an equibiaxial stress and isotropical physical properties in Pd2 Si. [Copyright &y& Elsevier]

A procedure to retrieve the three-dimensional strain and composition fields of single-crystalline nanoparticles using a combination of anomalous and coherent x-ray diffraction was developed. The applicability of the method was demonstrated using numerically generated data for AgIAu core-shell nanowires for which the epitaxy-induced strain field was simulated by the use of the finite element method for infinitely long nanowires with either abrupt ("as-prepared") or diffuse ("as-annealed") interfaces between core and shell. First, the influence of the elemental distribution and the associated inhomogeneous strains on the x-ray diffraction patterns were described. Next, the diffraction patterns as determined for different x-ray energies were inverted by applying phase retheval algorithms. Only if diffraction patterns at different energies are available and inverted can the concentrations and displacements be obtained subject to specific assumptions. [ABSTRACT FROM AUTHOR]

Plastic relaxation and formation of defects are crucial issues in the epitaxial growth of nanoparticles and thin films. Indeed, defects generate local stress in the crystalline lattice, which affects their surroundings and may lead to undesired effects such as reduced charge-carrier lifetime or nonradiative recombinations. Here, we use a nondestructive method based on x-ray diffuse scattering close to forbidden reflections to identify the defect types with a high sensitivity and quantify their average size and strain field. Combined with transmission electron microscopy, it offers opportunities to track both ensemble average and single defects inside three-dimensional structures. These techniques have been applied to partially embedded and high-Ge-content (xGe=0.87±0.06) dots selectively grown in 20-nm-sized pits on Si(001) surfaces through openings in a SiO2 template. The stress in the 20-nm-wide Ge islands is relaxed not only by interfacial dislocations but also by microtwins and/or stacking faults located at the interface, proving the importance of {111} planes and twinning in the relaxation process of nanometer-size Ge dots. [ABSTRACT FROM AUTHOR]

Abstract: We investigate the morphology of islands obtained by epitaxial growth of Ge on Si(001). During a low growth rate or during annealing and depending of the quench method, we observe the formation of a new type of superdomes, which exhibit additional {15323} facets, an increase of their {001} and {105} facet area on their top and a smaller aspect ratio compared to known superdomes. This flat-top superdome shape results from the complex evolution of domes and superdomes: coalescence, intermixing and ripening. Dome or superdome coalescence which results in the newly observed shape appears as a dominant pathway towards dislocation nucleation for the investigated temperature range. [Copyright &y& Elsevier]

Abstract: The growth mode, strain state and shape of Ge islands were analyzed in situ, during their growth on Si(001), by combining Grazing Incidence Small Angle X-ray Scattering (GISAXS) and Grazing Incidence X-ray Diffraction (GIXD) measurements. GISAXS measurements provide the detailed evolution of the shape of the grown quantum dots (QDs). GIXD allows the monitoring of the island nucleation and the strain state of the QDs. The shape, size, strain and interdiffusion are found to strongly depend on the growth temperature between 773 K and 923 K. At low T, the 3D islands are small, nearly fully relaxed and do not strain the substrate. At higher T, larger islands with significant Si content are grown, and induce deformation in the silicon substrate. [Copyright &y& Elsevier]

Abstract: The growth mode, strain state and shape of Ge islands were analyzed in situ, during their growth on Si(001), by combining grazing incidence small angle X-ray scattering (GISAXS) and X-ray diffraction (GIXD) measurements. GISAXS measurements provide the detailed evolution of the shape of the grown quantum dots (QDs) and allow characterizing the degree of ordering. GIXD allows monitoring the island nucleation, the evolution of the in-plane size and the epitaxial orientation of the QDs, as well as the diffusion of the wetting layer into the islands during growth. It is found that for a deposition temperature of 500°C, an amount of about one atomic layer is transported from the four monolayers (ML) thick wetting layer into the 3D islands. [Copyright &y& Elsevier]

Plastic relaxation and formation of defects is a crucial issue in the epitaxial growth of nanoparticles and thin films. Here, we report an in situ non-destructive method based on x-ray diffuse scattering close to forbidden reflections to study the formation of defects during the growth of Ge islands on Si(001). The dependence of in-plane spacing between interfacial dislocations, defect size, and density is analyzed as a function of Ge-deposit. It is found that the introduction of additional defects is preferred to relieve strain during growth. [ABSTRACT FROM AUTHOR]

Composition and strain inhomogeneities strongly affect the optoelectronic properties of InGaN but their origin has been unclear. Here we report real-time x-ray reciprocal space mapping that reveals the development of strain and composition distributions during metal-organic chemical vapor deposition of InxGa1-xN on GaN. Strong, correlated inhomogeneities of the strain state and In fraction x arise during growth in a manner consistent with models for instabilities driven by strain relaxation. [ABSTRACT FROM AUTHOR]

Experiments and numerical simulations based on finite element modeling show that the x-ray intensity scattered by comparatively large nanostructures on a substrate is not simply related to their strain in experiments using either grazing incidence or exit because of multiple scattering effects. However, whatever the nanostructure size, the composition profiles are correctly extracted from grazing incidence multiwavelength anomalous scattering. These effects are illustrated for the structural analysis of Ge dome-shaped islands grown on Si(001). [ABSTRACT FROM AUTHOR]

The growth of Ge on Si(001) is investigated in situ at 500 and 600 °C, combining grazing incidence diffraction, multiple wavelength anomalous diffraction, and small angle scattering. This allows probing simultaneously the island shape, strain state, composition, and the transition from wetting layer to island growth. At 500 °C no intermixing occurs. The wetting layer is found to decrease by one atomic layer at the onset of island nucleation. At 600 °C interdiffusion plays an important role in strain relaxation leading to a more stable wetting layer. Small angle scattering yields the island morphology and shows the transition from pyramids to multifacetted domes. [ABSTRACT FROM AUTHOR]

Fast-scanning X-ray microscopy is used to directly visualize the local strain and lattice tilt in the silicon neighboring Through Silicon Vias (TSVs). Strain variations of the order of 10 −4 were detected and results show that the silicon is slightly strained at room temperature ( | ε 335 | < 0.06 % ) with maximum close to the oxide/copper interface, after the completion of copper filled TSVs process. Finite element analysis was carried out and compared with experimental data obtained with synchrotron X-rays. Using the elements birth and death technique with commercial software ANSYS, 3D strains are simulated in a complete TSV structure. Numerical results are in good agreement with extracted strains from diffraction data. [ABSTRACT FROM AUTHOR]

This paper presents a study of the spatial distribution of strain and lattice orientation in CMOS fabricated strained Ge microstripes using high resolution x-ray micro-diffraction. The recently developed model-free characterization tool, based on a quick scanning x-ray diffraction microscopy technique can image strain down to levels of 10-5 (δa/a) with a spatial resolution of ~0.5 μm. Strain and lattice tilt are extracted using the strain and orientation calculation software package X-SOCS. The obtained results are compared with the biaxial strain distribution obtained by lattice parameter-sensitive μ-Raman and μ-photoluminescence measurements. The experimental data are interpreted with the help of finite element modeling of the strain relaxation dynamics in the investigated structures. [ABSTRACT FROM AUTHOR]

This paper presents a study of the spatial distribution of strain and lattice orientation in CMOSfabricated strained Ge microstripes using high resolution x-ray micro-diffraction. The recently developed model-free characterization tool, based on a quick scanning x-ray diffraction microscopy technique can image strain down to levels of 10-5 (△a/a) with a spatial resolution of ~0.5 μm. Strain and lattice tilt are extracted using the strain and orientation calculation software package X-SOCS. The obtained results are compared with the biaxial strain distribution obtained by lattice parameter-sensitive i-Raman and i-photoluminescence measurements. The experimental data are interpreted with the help of finite element modeling of the strain relaxation dynamics in the investigated structures. [ABSTRACT FROM AUTHOR]

Silicidation of Ni ultra-thin films on Si(001) substrates was investigated from room temperature to 500°C. In situ X-ray diffraction (XRD) experiments were performed to follow the reaction evolution. Transmission electron microscopy (TEM) and atomic probe tomography (APT) analyses highlight the formation of NiSi at low temperature (200°C). A peculiar phase sequence is evidenced for the thinnest deposited Ni film for which the NiSi phase forms from the low temperatures. Structural analyses of the formed silicides indicate that the NiSi phase grows in axiotaxy with the substrate at 200°C whereas NiSi2 rods form at higher temperatures. [ABSTRACT FROM AUTHOR]

Multi‐wavelength (mw) Bragg coherent X‐ray diffraction imaging (BCDI) is demonstrated on a single Au particle. The multi‐wavelength Bragg diffraction patterns are inverted using conventional phase‐retrieval algorithms where the dilation of the effective pixel size of a pixelated 2D detector caused by the variation of the X‐ray beam energy is mitigated by interpolating the raw data. The reconstructed Bragg electron density and phase field are in excellent agreement with the results obtained from conventional rocking scans of the same particle. Voxel sizes of about 63 nm3 are obtained for reconstructions from both approaches. Phase shifts as small as 0.41 rad, which correspond to displacements of 14 pm and translate into strain resolution better than 10−4 in the Au particle, are resolved. The displacement field changes shape during the experiment, which is well reproduced by finite element method simulations considering an inhomogeneous strained carbon layer deposited on the Au particle over the course of the measurements. These experiments thus demonstrate the very high sensitivity of BCDI and mw‐BCDI to strain induced by contaminations. Furthermore, mw‐BCDI offers new opportunities for in situ and operando 3D strain imaging in complex sample environments. [ABSTRACT FROM AUTHOR]

Systematic tensile tests were performed on single defect‐free ⟨110⟩ Au nanowires grown by physical vapor deposition while simultaneously recording three‐dimensional Bragg peaks using coherent X‐rays. The trajectory of three‐dimensional Bragg peaks in reciprocal space during tensile testing allowed for measurements of the evolution of strains and rotations of the nanowire, thus sensitively uncovering the full deformation geometry of the nanowire. The transition from elastic to plastic deformation is accompanied by rotations of the nanowire as quantified by analysis of the motion of Bragg peaks, showing the importance of boundary conditions in interpreting nanoscale mechanical deformations. [ABSTRACT FROM AUTHOR]

Structural quality and stability of nanocrystals are fundamental problems that bear important consequences for the performances of small-scale devices. Indeed, at the nanoscale, their functional properties are largely influenced by elastic strain and depend critically on the presence of crystal defects. It is thus of prime importance to be able to monitor, by noninvasive means, the stability of the microstructure of nano-objects against external stimuli such as mechanical load. Here we demonstrate the potential of Bragg coherent diffraction imaging for such measurements, by imaging in 3D the evolution of the microstructure of a nanocrystal exposed to in situ mechanical loading. Not only could we observe the evolution of the internal strain field after successive loadings, but we also evidenced a transient microstructure hosting a stable dislocation loop. The latter is fully characterized from its characteristic displacement field. The mechanical behavior of this small crystal is clearly at odds with what happens in bulk materials where many dislocations interact. Moreover, this original in situ experiment opens interesting possibilities for the investigation of plastic deformation at the nanoscale. [ABSTRACT FROM AUTHOR]

The strain distribution induced by TSVs is extensively studied in silicon by using submicron resolution synchrotron X-ray diffraction techniques. Simulations with finite elements are performed to interpret the experimental strain results. Stress and strain in silicon are found to be small at room temperature (< 7 × 10 − 5 ), while measurements and simulations at annealing temperature (400 °C) show a reverse sign of strain and support a plastic behavior of copper in some regions of the TSV. [ABSTRACT FROM AUTHOR]

The nucleation and the evolution of dislocations in SiGe/Si(001) films can be controlled and confined along stripes aligned along pits carved in the substrate, leaving micrometric coherent areas free of dislocations. In this work, we have addressed the stability of such metastable areas versus, film thickness, different Ge contents (xGe=10%-30%) and larger pit-pattern periods, revealing the flexibility and effectiveness of this method even for coherent areas of about 64 µm². The thermal stability of such configuration has been finally verified by post-growth annealing treatment, in order to simulate device processing. Finally, µRaman spectroscopy and X-ray nanodiffraction have been used to characterize the periodic strain variations across the pattern. [ABSTRACT FROM AUTHOR]

In-situ synchrotron x-ray observations reveal that the ferroelectric behavior of epitaxial (001) PbTiO3 thin films grown on (110) DyScO3 substrates depends on both film thickness and interfacial electrical properties. A 92-nm-thick film was found to exhibit an a/c domain structure with a ferroelectric Curie temperature similar to that theoretically predicted based on the strain state. In contrast, 6-nm-thick films contained only c-oriented domains, and the ferroelectric behavior was found to depend strongly on the nature of the electrical boundary condition at the buried interface. [ABSTRACT FROM AUTHOR]

Abstract: The strain field of individual epitaxial sub-micrometric copper islands is studied using coherent X-ray diffraction and finite element modelling. The strain inhomogeneity in each island is so large that the characteristic features of the island shape tend to disappear in the diffraction pattern, which is dominated by strain effects. The model confirms the tensile strain imposed to the island by the thermal mismatch occurring during the preparation of the samples. An evaluation of the residual strain is obtained by qualitatively fitting the diffraction data. [Copyright &y& Elsevier]

Mechanical deformation of a SiGe island epitaxically grown on Si(001) was studied by a specially adapted atomic force microscope and nanofocused X-ray diffraction. The deformation was monitored during in situ mechanical loading by recording three-dimensional reciprocal-space maps around a selected Bragg peak. Scanning the energy of the incident beam instead of rocking the sample allowed the safe and reliable measurement of the reciprocal-space maps without removal of the mechanical load. The crystal truncation rods originating from the island side facets rotate to steeper angles with increasing mechanical load. Simulations of the displacement field and the intensity distribution, based on the finite-element method, reveal that the change in orientation of the side facets of about 25° corresponds to an applied pressure of 2-3 GPa on the island top plane. [ABSTRACT FROM AUTHOR]

Ge-rich and N-doped Ge-Sb-Te thin films and patterned structures for memory applications are investigated in situ during annealing up to 500 °C with a heating rate of 2 °C/min using synchrotron x-ray diffraction. The initial material is amorphous. Under these annealing conditions, Ge crystallization occurs at 340 °C and precedes the one of cubic Ge 2 Sb 2 Te 5 by about 15 °C. In situ monitoring of diffraction allows for a quantification of crystallized quantity, grain size and elastic strain during the material transformation. Increasing N doping reduces the amount of crystallized Ge and Ge grain size. These results bring important insights into the multiphase crystallization of Ge-rich GST phase change materials for memory applications. [Display omitted] • in-situ synchrotron x-ray diffraction at DiffAbs beamline (SOLEIL synchrotron). • Monitoring of crystallization of Ge-rich N-doped Ge-Sb-Te thin films and nanostructures. • Ge crystallizes before GST (15 °C difference in crystallization temperature). • Thermoelastic behavior is different between films and patterned structures and is dominated by Ge. • Nitrogen doping strongly reduces Ge crystallization. [ABSTRACT FROM AUTHOR]

Review: 96 refs. [ABSTRACT FROM AUTHOR]

The upgraded ID01 beamline now offers a coherent X-ray probe, 56 nm × 141 nm in size (full width half maximum), combined with access to large swathes of reciprocal space with an area detector and sufficient working distance to host various sample environments. Coherent diffraction imaging at Bragg reflections offers picometre sensitivity to lattice distortions in crystals and access to the full strain tensor, in the case where three or more non-coplanar reflections are measured. Defects may have a strong effect on the physical properties of materials. As the majority of defects produce lattice distortions, hence these can be imaged. Here we describe the instrumentation at ID01 required to produce such foci and the protocols employed to ensure reliable data acquisition. The wavefront of the incident beam must be coherent in order to observe interference. Thus the coherent probe is recovered online via ptychography on a reference structure at the beginning of every experiment, and can be executed at any time to confirm beam quality and maintain experimental consistency. Due to the small source size in the vertical direction a diffraction limited spot is achieved, whereas in the horizontal the beam size is defined by the image of the source. With the upgrade of the ESRF this asymmetry is supposed to decrease substantially, and will be accompanied by an increase in coherent flux density by a factor of 30–100. [ABSTRACT FROM AUTHOR]