DiffAbs Beamline Research Articles

Dehydroxylation of Kaolinite and Halloysite-Rich Samples: An In Situ Study of the Texture and Structural Evolutions

Halloysite and kaolinite are dioctahedral TO phyllosilicates that drive the interest of scientists for formulating environmentally friendly materials, and consequently in the field of ceramics. The main scope of this study was the understanding of the texture evolution upon the dehydroxylation reaction and the influence of the presence of halloysite. In situ synchrotron (002) and (111) poles figures were recorded on the DiffAbs beamline at SOLEIL Synchrotron, from room temperature to 1000 °C, on kaolinite and/or halloysite-rich samples shaped by tape casting. Commercial kaolins and halloysite provided by Imerys company were used. The samples were labeled KRG100, KCS100, H100, KRG50H50 and KRG59H50 in relation with the wt. % of kaolin (KRG, KCS) or halloysite (H) clays. In samples KCS100 and KRG100, a strong texture was observed until in situ annealing at 700 °C, with respect to the c-axis of kaolinite. On the contrary, the texture with respect to the c-axis of halloysite for the sample H100 was weak whatever the temperature was. Moreover, this weak texture disappeared before the complete dehydroxylation of halloysite. This is due to the opening of some halloysite tubes. When considering the samples KRG50H50 and KCS50H50, a significant texture was observed with the c-axis preferentially oriented perpendicular to the sample surface. The presence of kaolinite platelets predominated onto the alignment of halloysites tubes. Furthermore, it was noted that the halloysite influenced the (002) diffracted intensity into the temperature range 20 °C to 400 °C. Above 400 °C, the behavior obtained for the (002) reflection in samples KRG50H50 and KCS50H50 was similar to the behavior noticed for pure kaolins KRG100 and KCS100, respectively. The dehydroxylation temperature range appeared to be relevant with combined effect of kaolinite and halloysite transformations arising from KRG100 or KCS100 and H100 samples. Therefore, the onset point of dehydroxylation is 550 °C ± 25 °C for KRG100, KCS100, KRG50H50 and KCS50H50. For the pure halloysite H100 sample, the dehydroxylation starts at the lower temperature 475 °C. It was also noted that during the dehydroxylation of kaolinite, the characteristic portion of ring related to the diffracted intensity of the (111) reflection located at χ = 45° tended to disappear above 550 °C and led to the formation of a new transitory phase with a (111) reflection with perpendicular alignment to the c-axis. Indeed, an epitaxial relationship with the (111) kaolinite reflection could be assumed. Further X-ray scattering experiments allowed highlighting the effective offset temperature of the dehydroxylation, which was identified as close to 720 °C. The metakaolinite achieved structural transformation to another transitory phase at 1000 °C.

The CirPAD, a circular 1.4 M hybrid pixel detector dedicated to X-ray diffraction measurements at Synchrotron SOLEIL.

One of the challenges of all synchrotron facilities is to offer the highest performance detectors for all their specific experiments, in particular for X-ray diffraction imaging and its high throughput data collection. In that context, the DiffAbs beamline, the Detectors and the Design and Engineering groups at Synchrotron SOLEIL, in collaboration with ImXPAD and Cegitek companies, have developed an original and unique detector with a circular shape. This detector is based on the hybrid pixel photon-counting technology and consists of the specific assembly of 20 hybrid pixel array detector (XPAD) modules. This article aims to demonstrate the main characteristics of the CirPAD (for Circular Pixel Array Detector) and its performance - i.e. excellent pixel quality, flat-field correction, high-count-rate performance, etc. Additionally, the powder X-ray diffraction pattern of an LaB6 reference sample is presented and refined. The obtained results demonstrate the high quality of the data recorded from the CirPAD, which allows the proposal of its use to all scientific communities interested in performing experiments at the DiffAbs beamline.

Lattice Strain Evolutions in Ni-W Alloys during a Tensile Test Combined with Synchrotron X-ray Diffraction.

Ni and Ni(W) solid solution of bulk Ni and Ni-W alloys (Ni-10W, Ni-30W, and Ni-50W) (wt%) were mechanically compared through the evolution of their {111} X-ray diffraction peaks during in situ tensile tests on the DiffAbs beamline at the Synchrotron SOLEIL. A significant difference in terms of strain heterogeneities and lattice strain evolution occurred as the plastic activity increased. Such differences are attributed to the number of brittle W clusters and the hardening due to the solid solution compared to the single-phase bulk Ni sample.

Microsecond time-resolved X-ray diffraction for the investigation of fatigue behavior during ultrasonic fatigue loading.

A new method based on time-resolved X-ray diffraction is proposed in order to measure the elastic strain and stress during ultrasonic fatigue loading experiments. Pure Cu was chosen as an example material for the experiments using a 20 kHz ultrasonic fatigue machine mounted on the six-circle diffractometer available at the DiffAbs beamline on the SOLEIL synchrotron facility in France. A two-dimensional hybrid pixel X-ray detector (XPAD3.2) was triggered by the strain gage signal in a synchronous data acquisition scheme (pump-probe-like). The method enables studying loading cycles with a period of 50 µs, achieving a temporal resolution of 1 µs. This allows a precise reconstruction of the diffraction patterns during the loading cycles. From the diffraction patterns, the position of the peaks, their shifts and their respective broadening can be deduced. The diffraction peak shift allows the elastic lattice strain to be estimated with a resolution of ∼10-5. Stress is calculated by the self-consistent scale-transition model through which the elastic response of the material is estimated. The amplitudes of the cyclic stresses range from 40 to 120 MPa and vary linearly with respect to the displacement applied by the ultrasonic machine. Moreover, the experimental results highlight an increase of the diffraction peak broadening with the number of applied cycles.

(Invited) Ultrathin Epitaxial Silicides for Semiconductor Contacts

Over the past decades, nickel mono-silicide NiSi has become one of the preferred materials to enhance contacting in silicon-based semiconductor devices. However, the formation of a useable NiSi contacting layer is challenged by the continued miniaturization in the micro-electronics industry. As the silicide thickness is reduced, it is more likely to agglomerate [D. Deduytssche et al., J. Appl. Phys. 98, 033526 (2005)]. Therefore it is crucial to stabilize silicide films, either by altering the microstructure of the NiSi phase or by exploring the use of alternative phases that are more resistant to agglomeration. However, De Keyser et al. [Appl. Phys. Letters. 96, 173503 (2010)] reported that below a critical thickness of 5 nm, annealing of ultrathin Ni films results in surprisingly stable silicide layers. In this work, we systematically investigated (1) the influence of Ni thickness on the formation of nickel silicides in the range between 0 and 15 nm, and (2) the influence of alloying elements (e.g. Al, Co, Pd, Ge and Pt) on the phase formation sequence and on the critical thickness phenomenon. Research on such ultra-thin films is very challenging using conventional lab-based XRD techniques. Therefore, the silicidation process was investigated in detail through XRD-based pole figure measurements at the DiffAbs beamline of the SOLEIL synchrotron. These measurements allow unambiguous phase identification, even if the formed silicide would exhibit a preferential orientation to the monocrystalline substrate. Furthermore, these synchrotron based pole figure measurements provided detailed texture information that helps to understand the observed shift in critical thickness and the morphological stability of the ultra-thin silicide layers. For an as deposited layer thickness above the critical thickness, we observed the sequential formation of Ni -> θ-Ni2Si (epitaxial) -> δ-Ni2Si -> NiSi, which agglomerates. Samples in the ultrathin regime (i.e. below the critical thickness, e.g. for 3nm pure Ni) instead exhibit a formation sequence identified as Ni -> θ-Ni2Si (epitaxial) -> NiSi2 (epitaxial). This finally formed NiSi2 is remarkably stable and does not suffer from agglomeration. The phase sequence changes at a critical thickness for pure Ni films around 5nm as-deposited thickness. Through alloying of the initial Ni layer, we could influence this critical thickness to higher (Al) and lower (Ge, Pd, Pt) values. Our pole figure measurements also showed that the interface alignment of these silicide grains with their surroundings, and the energetic cost of creating such an interface, plays a crucial role during the phase formation. In summary, we report that the phase formation sequence during the Ni salicidation process severely changes at a critical thickness of 5nm. Pole figure measurements show that the thicker films form intermediate Ni-rich phases which subsequently form agglomerating NiSi. Thinner films, however, show a simplified formation sequence which results in the formation of epitaxial, non-agglomerating NiSi2. Secondly, we demonstrate that this critical thickness can be influenced to higher or lower values through the addition of alloying elements, an effect that can be understood through the effect of mixing entropy. Furthermore, crystallographic alignment matching at the interface is a crucial parameter controlling the phase formation kinetics in these sub-10nm thick films.

Flyscan opportunities in medicine: the case of quantum rattle based on gold quantum dots.

The new rapid scan method, Flyscan mode, implemented on the DiffAbs beamline at Synchrotron SOLEIL, allows fast micro-X-ray fluorescence data acquisition. It paves the way for applications in the biomedical field where a large amount of data is needed to generate meaningful information for the clinician. This study presents a complete set of data acquired after injection of gold-cluster-enriched mesoporous silica nanospheres, used as potential theranostic vectors, into rats. While classical X-ray fluorescence investigations (using step-by-step acquisitions) are based on a limited number of samples (approximately one per day at the DiffAbs beamline), the Flyscan mode has enabled gathering information on the interaction of nanometer-scale vectors in different organs such as liver, spleen and kidney at the micrometer scale, for five rats, in only a single five-day synchrotron shift. Moreover, numerous X-ray absorption near-edge structure spectra, which are beam-time-consuming taking into account the low concentration of these theranostic vectors, were collected.

Nano-structuration effect on the mechanical behavior of gold thin films studied by 2D synchrotron x-ray diffraction

Thin film technology is pervasive in microelectronics, and in optical, magnetic or micro-mechanical devices. The mechanical performance of such nanoscale structure is crucial for applications since it is related to device lifetime. Furthermore, the mechanical behavior of nanostructured materials is still not well known. In this work, nanostructured gold thin films with different thicknesses have been elaborated by sequenced ion beam sputtering to study size effect. The grain size is controlled by stopping the grain growth during the thin film growth. Using the biaxial tensile setup developed at the DiffAbs beamline of the French synchrotron facility SOLEIL, x-ray diffraction (XRD) measurements have been performed during controlled biaxial deformation tests on gold thin films deposited on Kapton substrate. Strain analysis of the gold thin films with different grain size and architecture has been achieved for a non equi biaxial loading with a force ratio of 0.8. XRD allows measuring the intra-granular strains using the so-called sin2ψ method while the macroscopic in-plane strains are measured simultaneously thanks to Digital Image Correlation. By analyzing the mechanical response of the different films, we conclude that gold thin films follow a plastic deformation mode whatever the grain size or thin film architecture.

Stress buildup during crystallization of thin chalcogenide films for memory applications: In situ combination of synchrotron X-Ray diffraction and wafer curvature measurements

Phase change materials (PCMs) such as Ge2Sb2Te5 (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 (30nm) 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.

Synchrotron X-ray diffraction of bole layers from Portuguese gilded baroque retables

Studies based on a scientific approach to materials and techniques used in Portuguese gilded retables from the Baroque are very scarce and focus particularly on works with erudite features and on the characterization of the superficial gold leaf. The conservation and appearance of gilded surfaces, however, depended on the qualities of the clayey ground layer underneath, which is the bole. Colour and texture are closely related to its mineralogical composition.Boles were healing clays. Red to orange varieties could also be used for gilding, usually agglutinated with animal glue when the gold surface was meant to be burnished. Armenian was the name used to identify the best quality material.Microsamples collected from erudite and popular gilded retables, respectively belonging to the city of Oporto and its rural surroundings, were selected for elemental and mineralogical characterization. It was intended to shed light on the characteristics of boles used in Portuguese retables and to understand if there are any differences between materials used in works of distinct artistic quality.Elemental analysis was performed through SEM–EDS. SR-XRD was used for phase identification, performed with a six-circle diffractometer at the DIFFABS beamline of SOLEIL Synchrotron. Portuguese clay standards of identifiable composition and provenance were also analysed.The results suggest that boles are mainly kaolinitic, with variable amounts of illite and smectite. Gypsum was used as an extender. Although the proportions of the main clay minerals are similar in erudite and popular works, in Oporto homogeneity is clearly higher.

Time-Resolved X-Ray Stress Analysis in Multilayered Thin Films during Continuous Loading: Use of 2D Remote Detection

Synchrotron X-ray diffraction is a powerful tool to analyse the mechanical behavior of multiphase materials due to its selectivity. Simultaneous stress analysis of both phases of a W/Cu thin multilayer has been performed during a continuous biaxial loading on DiffAbs beamline at SOLEIL synchrotron (France). The use of a 2D detector with a large sample-detector distance is shown to give relatively accurate applied stress analysis even if only a small part of the usual ψ range of the sin2ψ method is considered. The results show the failure of the thin film multilayer while the W components are still under a strong compressive stress state of-3 GPa. It is concluded that the mechanical behavior is in fact mainly governed by the residual stress state.

Fast pole figure acquisition using area detectors at the DiffAbs beamline – Synchrotron SOLEIL

Structural anisotropy, for example texture, may govern important physical properties of thin film, such as electrical, magnetic and/or mechanical ones. Texture (orientation information) is typically observed and quantified by the measurement of so-called pole figures. An optimized experimental approach implemented at the DiffAbs beamline (Synchrotron SOLEIL) is presented here. Using an X-ray pixel area detector and synchrotron radiation sources, a complete pole figure (with resolutions adapted for metallic textured thin films, typically of the order of a few degrees) can be measured in time intervals as short as one minute. The necessary corrections enabling complete pole figure retrieval from the experimental data using this optimized approach are provided and discussed. A gain in measuring time by up to two orders of magnitude is found with respect to the use of a point detector (classical approach) under the same experimental conditions. Data measured using these two approaches are shown, compared and discussed.

Stress evaluation in thin films: Micro-focus synchrotron X-ray diffraction combined with focused ion beam patterning for do evaluation

Nanocrystalline metallic coatings of sub-micron thickness are widely used in modern microelectronic applications. In X-ray diffraction experiments to determine both the residual and applied stresses in nanocrystalline coatings, one difficult challenge that comes up invariably is the determination of the strain-free lattice spacing do. The present study addresses this challenge by using the focused ion beam (FIB) to generate a built-in strain-free reference by patterning (milling) a 50×50μm2 region of the coating to produce an array of small stress-relieved “islands” ~0.8×0.8μm2 each. Transmission X-ray diffraction setup was used for data collection at DIFFABS beamline (Synchrotron SOLEIL, France). A 150nm-thick multi-layered W–Cu nano-composite thin film on polyimide (Kapton®) substrate was studied. The samples were loaded incrementally using a compact uniaxial loading device, and micro-beam diffraction data were collected on and away from the reference array. It was shown experimentally that the “island” array remained approximately strain free throughout the experiment, providing an on-board do lattice spacing reference. The changing lattice spacing d in the coating was also monitored away from the array, to deduce the elastic strain evolution during deformation. The results and their implications are presented and discussed.

Non-equibiaxial deformation of W/Cu nanocomposite thin films on stretchable substrate: Effect of loading path

In situ biaxial tensile tests were carried out on W/Cu nanocomposite thin films deposited on a polyimide cruciform substrate. A biaxial testing machine developed on the DiffAbs beamline at the French SOLEIL synchrotron allows for scrutinizing the mechanical behaviour of crystalline thin films at the micro-scale and the macro-scale using simultaneously synchrotron X-ray diffraction and digital image correlation techniques. Both strain analyses have been performed for two controlled non-equibiaxial loading paths: loading ratios of 0.8 and 0.33. The mechanical response is analysed and compared for the two loading ratios.

Yield surface of polycrystalline thin films as revealed by non-equibiaxial loadings at small deformation

A biaxial device developed at DiffAbs beamline of the SOLEIL synchrotron facility has been employed to determine the applied strains in film–substrate composites using both X-ray diffraction and digital image correlation measurements. Such an experimental combination is used for the first time to determine the yield surface of a polycrystalline thin film deposited on a polyimide substrate. In situ biaxial tensile tests under different biaxial planar load ratios were performed on W/Cu nanocomposite thin films deposited on flexible substrates. The effect of loading path on the yield stress of W/Cu nanocomposites is presented by considering a large range of proportional loadings. By comparing experimental results with theoretical models, this study reveals the brittle behaviour of W/Cu nanocomposite thin films at small deformations.

Beamline fast and automatic attenuation system for X-Ray detectors at Synchrotron Soleil

Attenuators are commonly used on beamlines to control incident photon flux. Attenuators are mainly controlled by software. In some experimental cases using various diffraction techniques, this architecture is not fast enough to manage high flux variation. The fast attenuation system inserts and extracts filters quickly, allowing very fast beam attenuation at the maximum rate allowed by the filter mechanism and the beam detector response. To build the solution, we used an off-the-shelf CPCI General Purpose board (GPIO) from TEWS that is based on a SPARTAN-3 Xilinx FPGA: We have developed a daughter board and an embedded VHDL program. The logic is dedicated to maintaining incident detector photon flux within an acceptable range for optimized measurements and protecting the X ray detector against over-exposure. This system is part of a continuous scan process. Some low level process logic is also embedded in order to optimize data exchange. During continuous scanning, this process allows each experimental data item collected to be associated with its corresponding photon flux value. This system is in operation on the SIXS beamline and will be soon installed on the DIFFABS beamline. This paper describes the principle and the results obtained with this solution and the possible improvements and perspectives (interfacing more complex detectors such as XPad).

Deformation modes of nanostructured thin film under controlled biaxial deformation

This paper reports on the mechanical behaviour of nanostructured W/Cu thin films deposited on Kapton® under controlled biaxial loadings thanks to a biaxial testing device developed on DiffAbs beamline at SOLEIL synchrotron (Saint-Aubin, France). In situ tensile tests were carried out combining 2D synchrotron X-ray diffraction (XRD) and digital-image correlation (DIC) techniques. First, the elastic behaviour of the composite metallic film — polymeric substrate was investigated under equi-biaxial and non-equi-biaxial loading conditions. The results show that the strain measurements (in the crystalline film by XRD and the substrate by DIC) match within 10−4. This result demonstrates the full transmission of strains in the elastic domain through the film-substrate interface and thus a good adhesion of the thin film to the substrate. The second part of the paper deals with higher strains response under equi-biaxial tensile tests. The elastic limit of the nanostructured W/Cu thin films was determined at the bifurcation point between strains obtained by XRD and DIC. Deformation mechanisms such as strain localisation and film fragmentation are proposed.

In situmulti-axial loading frame to probe elastomers using X-ray scattering

An in situ tensile-shear loading device has been designed to study elastomer crystallization using synchrotron X-ray scattering at the Synchrotron Soleil on the DiffAbs beamline. Elastomer tape specimens of thickness 2 mm can be elongated by up to 500% in the longitudinal direction and sheared by up to 200% in the transverse direction. The device is fully automated and plugged into the TANGO control system of the beamline allowing synchronization between acquisition and loading sequences. Experimental results revealing the evolution of crystallization peaks under load are presented for several tension/shear loading sequences.

Combined synchrotron X-ray and image-correlation analyses of biaxially deformed W/Cu nanocomposite thin films on Kapton

In situbiaxial tensile tests within the elastic domain were conducted with W/Cu nanocomposite thin films deposited on a polyimide cruciform substrate using a biaxial testing machine developed on the DiffAbs beamline at the Synchrotron SOLEIL. The mechanical behaviour of the nanocomposite was characterized at the micro- and macroscales using synchrotron X-ray diffraction and digital image-correlation techniques simultaneously. Strain analyses for equibiaxial and non-equibiaxial loading paths were carried out. The results show that the two strain measurements match to within 1 × 10−4in the elastic domain for strain levels less than 0.3% and for both loading paths.

Controlled biaxial deformation of nanostructured W/Cu thin films studied by X-ray diffraction

The deformation behaviour of 150 nm thick W/Cu nanocomposite deposited on polyimide substrates has been analysed under equi-biaxial tensile testing coupled to X-ray diffraction technique. The experiments were carried out using a biaxial device that has been developed for the DiffAbs beamline of SOLEIL synchrotron source. Finite element analysis has been performed to study the strain distribution into the cruciform shape substrate and define the homogeneous deformed volume. X-ray measured elastic strains in tungsten sub-layers could be carried out for both principal directions. The strain field was determined to be almost equi-biaxial as expected and compared to finite element calculations.

Mechanical characterization of nanostructured thin films at different scales

The mechanical behaviour of multilayered W/Cu thin films on polyimide substrate has been investigated at different scales and using complementary X-ray techniques and compared to finite element analysis. Mechanical testing has been carried out using a new biaxial tensile machine which allow s for testing in controlled biaxial loading condition. This device has been developed f or synchrotron measurements at DiffAbs beamline of the French synchrotron radiatio n facility (SOLEIL, Saint Aubin).