Grazing Incidence X-ray Diffraction Method Research Articles

Surface stress release in AlCrN coatings determined by synchrotron radiation multi-reflection grazing-incidence X-ray diffraction

In this work, the residual stress distribution of c. 3.8 μm arc-evaporated AlCrN coatings was investigated by the synchrotron radiation multi-reflection grazing-incidence X-ray diffraction method. Ar ion bombardment post-treatment was also used to tune the stresses in the AlCrN coating to elucidate the evolution of stress therein. The result showed that the as-deposited AlCrN coating showed large surface stress of −1500 MPa, this sharply decreased in magnitude to −800 MPa in the internal coating. Ar ion bombardment (post-treatment) could significantly reduce the surface stresses by around −1000 MPa and the interior stresses by around −400 MPa for an AlCrN coating, the “shot peening” effect arising therefrom could promote migration and diffusion of the adatoms, which contributed to the reduction of the micro-strain and interior stress. Furthermore, Ar ion bombardment also promoted the growth of surface grains, which also contributed to the stress reduction in the near-surface region of the AlCrN coating. In addition, Ar ion bombardment could increase the substrate stresses from −32 MPa to −210 MPa. The results suggested that internal stress reduction could be achieved by promoting the migration and diffusion of adatoms.

Increase in the density of Sr2Fe1.5Mo0.5O6-δ membranes through an excess of iron oxide: The effect of iron oxide on transport and kinetic parameters

Due to its widespread application in modern industry, the ongoing development of all the most important technological directions in the field of sensors, oxygen membranes, and reforming is undoubtedly a promising trend in world research and development (R&D). The search for modern highly oxygen-conducting materials used as oxygen separation membranes continues today. In this work, we investigated the following well-proven oxygen-conducting material, such as strontium ferrite-molybdate Sr2Fe1.5Mo0.5O6-δ. As an alternative for obtaining high-density ceramics, we used a co-synthesis method with a sintering additive (Fe2O3). We investigated the influence of sintering additive on the structural characteristics by certifying the phase composition by X-ray phase analysis; matrix continuity and volume distribution of Fe2O3 by secondary electron microscopy using energy dispersive X-Ray analysis; and elemental analysis of ceramic surface by X-ray photoelectron spectroscopy. The influence of Fe2O3 on the electrical conductivity was investigated using the four-probe DC method in the temperature range 100–800 °C in air. The kinetic dependences of 18O isotope-labeled oxygen on time were also obtained in the temperature range 600–800 °C and absolute oxygen pressure of 10−2 atm. The rate of heterogeneous oxygen exchange, the oxygen diffusion coefficient, and the corresponding rates of elementary processes of dissociative adsorption and incorporation of oxygen are calculated. Furthermore, it was revealed that the diffusion coefficient in the near-surface area significantly differs from the bulk one. As a consequence, this paper evaluates the observed effect and carefully analyzes the results obtained. All considered material parameters were analyzed and the regularities of the influence of surface composition on the rate-determining step of oxygen exchange were revealed. This research has made it possible to obtain dense ceramics at low temperatures and to identify a step that determines the rate of the oxygen exchange process. Finally, how strontium molybdate based thin layer on the surface and between the grains of the polycrystalline strontium ferrite-molybdates influence on the oxygen surface exchange and diffusivity is considered. The presence of such a phase in the form of a nanosized layer on the surface was convincingly proven by X-ray photoelectron spectroscopy and a grazing incidence X-Ray Diffraction method. Furthermore, the corresponding layer thickness, as well as the oxygen diffusion coefficients of the near-surface layer and the interface layer, were estimated experimentally and by modeling.

Gradient of Residual Stress and Lattice Parameter in Mechanically Polished Tungsten Measured Using Classical X-rays and Synchrotron Radiation

In this work, the stress gradient in mechanically polished tungsten sample was studied using X-ray diffraction methods. To determine in-depth stress evolution in the very shallow subsurface region (up to 10 μm), special methods based on reflection geometry were applied. The subsurface stresses (depth up to 1 μm) were measured using the multiple-reflection grazing incidence X-ray diffraction method with classical characteristic X-rays, while the deeper volumes (depth up to 10 μm) were investigated using energy-dispersive diffraction with white high energy synchrotron beam. Both complementary methods allowed for determining in-depth stress profile and the evolution of stress-free lattice parameter. It was confirmed that the crystals of tungsten are elastically isotropic, which simplifies the stress analysis and makes tungsten a suitable material for testing stress measurement methods. Furthermore, it was found that an important compressive stress of about − 1000 MPa was generated on the surface of the mechanically polished sample, and this stress decreases to zero value at the depth of about 9 μm. On the other hand, the strain-free lattice parameter does not change significantly in the examined subsurface region.

Precise structural analysis of polymer materials using synchrotron X-ray scattering and spectroscopic methods

Polymers can exist in many different conformations and exhibit a variety of unique and complicated hierarchical structures, which are dominated mainly by entropy and sometimes by kinetics rather than thermodynamics due to the intrinsic high viscosity, polydispersity, and so on. The physical properties of polymeric materials are determined not only by their primary structures but also by their higher order (hierarchical) structures. Hence, precise determination of the structures at all spatial scales is essential to control the physical properties of polymeric materials. This focus review details the use of various characterization techniques, including variable-temperature (VT) synchrotron (SR) X-ray scattering, VT SR X-ray diffraction, and infrared p-polarized multiple-angle incidence resolution spectrometry (pMAIRS), to determine the structure of fully liquid-crystalline ABA-type triblock copolymers, highly crystalline aromatic polyimides, and thin-film polyimides, respectively. The advantages of these methods are briefly reviewed, and the relationship between the macroscopic physical properties and the inherent microstructure is discussed. Physical properties of polymer materials are deeply related to not only the primary structure but also the higher ordered structure such as periodic structures and molecular orientation. If the target material consists of ordered and non-ordered region, the former structure can be selectively detected by X-ray scattering method, whereas structural information of both the regions is obtained by infrared absorption spectroscopy. Particularly for thin film materials, infrared pMAIRS (p-polarized multiple-angle incidence resolution spectroscopy) and GI-XRD (grazing incidence X-ray diffraction methods are very useful for precise structural analyses.

Direct observation of amorphous to crystalline phase transitions in Ge–Sb–Te thin films by grazing incidence X-ray diffraction method

Ge–Sb–Te (GST)-based PCM alloys are currently used in optical data storage. The crystallization of GST materials is the rate-limiting step for these devices, hence a deeper knowledge of the crystallization mechanism is crucial for insightful development of faster devices. In the present work, the diffraction patterns for GST-225 thin films are studied using the in situ Grazing Incidence X-ray Diffraction method upon heating. It is shown that initial amorphous film in the temperature range from 120 to 140 °C is crystallized into two phases-cubic GST-225 (Fm$${\bar{3}}$$m), and trigonal GST-147 (P$${\bar{3}}$$m1). The crystallized film is stressed and highly textured, and should be characterized by the value of the lattice parameters averaged over all crystallographic planes. The structural transition of GST-225 from cubic to trigonal phase begins at T > 180 °C. The appearance of large-scale inhomogeneities in GST-225 film at T ≥ 100 °C indicates that the process of rearrangement of atoms Ge, Sb, and Te in the as-deposited amorphous film begins long before the onset of crystallization.

Non-destructive Surface Residual Stress Profiling by Multireflection Grazing Incidence X-Ray Diffraction: a 7050 Al Alloy Study

The multireflection grazing incidence X-ray diffraction method (MGIXD) was used to analyze the surface residual stresses in 7050 Al alloy samples. This technique can provide a non-destructive stress profile in function of sample depth, avoiding the relaxation effects intrinsic to destructive methods. The state of residual stress in aeronautical aluminium samples was modulated by milling and shot peening processes. After structural characterization, the residual stress states of the samples were analyzed by multireflection and conventional stress measurement methods. The milled samples presented tensile surface residual stress relaxation attributed to thermal effects and the shot peened samples showed strong compressive stress at sub-surface, which intensity was reduced near the surface. The residual stress profiles of the Al samples were obtained by MGIXD method that evidenced properties commonly undetected in conventional residual stress studies.

Multireflection grazing-incidence X-ray diffraction: a new approach to experimental data analysis

The multireflection grazing-incidence X-ray diffraction method is used to test surface stresses at depths of several micrometres in the case of metal samples. This work presents new ways of analysing experimental data obtained by this method for Ni samples exhibiting significant elastic anisotropy of crystals. Three different methods of determining biaxial stresses and lattice parameter were compared. In the first approach, the calculations were performed using the linear least-squares method, and then two simplified procedures based on simple linear regression (weighted and non-weighted) were applied. It was found that all the tested methods give similar results, i.e. almost equal values of the determined stresses and lattice parameters and the uncertainties of their determination. The advantage of analyses based on simple linear regression is their simplicity and straightforward interpretation, enabling easy verification of the influence of the crystallographic texture and the presence of shear stresses, as well as graphical determination of the stress-free lattice parameter.

Investigation of short-term, high-temperature oxidation of AlCrN coating on WC substrate

A surface analysis was performed on an aluminum chromium nitride (AlCrN) coating formed on a tungsten carbide (WC) substrate subjected to short-term (in minutes) oxidation at an elevated temperature (900 °C) using focused ion beam (FIB), X-ray photoelectron spectroscopy (XPS), grazing incidence X-ray diffraction (GI-XRD), and laser-induced breakdown spectroscopy (LIBS). To separately analyze a coating with a thickness of several micrometers, the GI-XRD method was used. For cross-sectional imaging, the samples were milled using an FIB system, and chemical bonding states and surface elemental concentrations were analyzed by XPS. Within just a few seconds, the color of the AlCrN coating surface changed irregularly and, after 10 min, the entire coating layer surface changed. The entire coating surface oxidation as discoloration progressed in partial areas after 30 min. Based on the GI-XRD and XPS results, after 1 min, alumina and chromium oxides formed on the outermost surface, and after 10 min, Cr-W and Co-W oxide phases appeared, resulting from a reaction with WC near the interface. The atomic concentration of nitrogen in the AlCrN coating decreased after few seconds on the outermost surface and was almost eliminated after 10 min; oxygen showed the opposite trend. Finally, the FIB and LIBS results showed that voids formed within the coating layer and interface at high temperatures, and diffusion of Al and Cr in subsequent reactions was identified. This work demonstrates interesting results from various analyses that differ from previously reported AlCrN coating oxidation behaviors, and could provide a better understanding of long-term reactions for the surface oxidation of AlCrN coatings at high temperatures.

Depth profile crystal orientation determination of Cu(In1−xGax)Se2 thin films by GIXRD method applying skin depth theory

In this study, Cu(In1−xGax)Se2 (CIGS) thin film was deposited on molybdenum (Mo) coated glass substrate by thermal co-evaporation technique and depth profile crystal orientation of the this film was examined by grazing incidence X-ray diffraction (GIXRD) method. The crystal structure of the CIGS thin film was determined within 20° to 80° (2θ) scanning range at 0.5° to 15° incidence angle of X-ray. Cross section images were investigated by scanning electron microscope measurements and these measurements showed that bilayer Mo thickness and CIGS thickness are approximately 480 nm and 2 µm, respectively. The surface roughness of films investigated by atomic force microscopy (AFM) and average roughness Ra was found 11.07 nm. According to GIXRD measurements; the interdiffusion of the constituent elements and their effect on the crystal structure were defined both electromagnetic field penetration (skin depth) and mass attenuation viewpoints, and also these results were supported by energy dispersive spectroscopy measurements. As a result, it was seen that the GIXRD method can be used with ease to define the crystal phase homogeneity and depth profile characterization of thin film volume applying skin depth theory.

Mechanical and structural properties of ODS RAF steels submitted to low-energy ions irradiation

The effect of ion implantation on mechanical and structural properties of 12%Cr ODS steel have been investigated. Specimens were submitted to single (He+ or Fe+) and dual ion beam (He+ and Fe+) implantation campaigns. Modification of three mechanical parameters: hardness, Young modulus and yield strength were characterized by means of nanoindentation technique. Structural properties were measured by using Grazing Incidence X-ray Diffraction (GIXRD) method. Correlation between obtained mechanical and structural results have been found. Recorded results show that ion-irradiation causes hardening effect which may be associated with creation of radiation defects and dislocation loops. The weakest effects have been observed for single He-ion implantation, whereas the dual beam irradiation led to significant change of all mechanical parameters. During structural analysis, small shifts of α-Fe peaks have been observed. Reported structural changes can be attributed to the effect of local stress introduced during ion irradiation.

Nanomechanical Imaging of the Diffusion of Fullerene into Conjugated Polymer.

The large Young's modulus difference between chemically modified fullerene (PCBM) and a conjugated polymer was used to nanomechanically map the diffusion of PCBM into PTB7, a high-efficiency low-band-gap conjugated polymer. The sharp tip in nanomechanical atomic force microscopy ensures a high-resolution nanomechanical characterization of the diffusion front, with the intrinsic benefits of revealing the mechanical properties of the mixtures. Localized structure changes induced by diffusion were investigated by grazing incidence X-ray diffraction methods. We found a most unusual diffusion behavior that shows Case II characteristics, where a front of PTB7 saturated with PCBM moves into the pure PTB7 with a linear time dependence. This diffusion is due mainly to a majority fraction of the disordered PTB7 that has continuous paths for PCBM diffusion without obvious energetic barriers, and as diffusion proceeds, the paths for diffusion gets larger, leading to a step in the concentration profile. The donor/acceptor-dependent diffusion constants may also contribute to the observed Case-II-like diffusion front.

Stress measurements by multi-reflection grazing-incidence X-ray diffraction method (MGIXD) using different radiation wavelengths and different incident angles

The presented study introduces the development of the multi-reflection grazing-incidence X-ray diffraction method (MGIXD) for residual stress determination. The proposed new methodology is aimed at obtaining more reliable experimental data and increasing the depth of non-destructive stress determination below the sample surface. To verify proposed method measurements were performed on a classical X-ray diffractometer (Cu Kα radiation) and using synchrotron radiation (three different wavelengths: λ = 1.2527 Å, λ = 1.5419 Å and λ = 1.7512 Å). The Al2017 alloy subjected to three different surface treatments was investigated in this study. The obtained results showed that the proposed development of MGIXD method, in which not only different incident angles but also different wavelengths of X-ray are used, can be successfully applied for residual stress determination, especially when stress gradients are present in the sample.

Equi-penetration grazing incidence X-ray diffraction method: Stress depth profiling of ground silicon nitride

In this work a new modification of the grazing incidence X-ray diffraction method for residual stress determination is presented. This equi-penetration grazing incidence X-ray diffraction method is especially suitable for the precise determination of the residual stress depth profile in materials. It originates from a sin2ψ approach based on the determination of the lattice spacing of various selected diffraction planes. Additionally, for each measurement the condition ∂τ/∂ψ=0 is here fulfilled and one dataset corresponds strictly to a specific mean penetration depth τ independent of the tilt angle ψ. This can be achieved by the individual adjustment of the incidence angle for each measured diffraction maximum. In the actual work, the influence of different surface finishes on the stress depth profile of commercial silicon nitride ceramic samples is investigated. The ground specimen displays an almost biaxial compressive stress parallel and near to the specimen surface of 3GPa, which decreases almost up to zero in a depth of 5μm. After the polishing process, the specimens show a strongly reduced compressive stress maximum at the surface of 1GPa, which diminishes similarly with increasing depth. The orientation between the stress component and the grinding direction is of minor influence. Furthermore, the influence of a possible residual stress component perpendicular to the sample surface is discussed.

High resolution X-ray and electron microscopy characterization of PZT thin films prepared by RF magnetron sputtering

Pb(Zr0.52Ti0.48)O3 (PZT) thin films grown on Pt/TiO2/SiO2/Si(1 0 0) substrates in the thickness range of ∼30–550 nm by radio frequency (RF) magnetron sputtering method under different sputtering pressures were studied in the present work. High resolution grazing incidence X-ray diffraction method for residual stress and electron microscopy, particularly cross sectional transmission electron microscopy (XTEM), were used to identify the crystalline phases, and structure of the thin films at the nano-scale. Microstructure of the ultrathin films in <50 nm thickness range, consists predominantly of para-electric, oxygen deficient pyrochlore phase of Pb2Ti2O6 structure co-existing with ferroelectric perovskite PZT phase in tetragonal form. In films with thickness around 500 nm, sputtering pressure shows a strong influence on the purity of PZT phase grown. High resolution X-ray diffraction method for wafer curvature measurement and Stoney's equation were used to evaluate the biaxial stress in the films. It is found that the ultrathin films are compressively stressed with high magnitude of the order of 2 GPa which gets reduced with increasing film thickness. In the thickness range of ∼500 nm, at an optimum sputtering pressure of 4.5 Pa, the stress becomes tensile in nature with a small magnitude of 2.3 MPa. At this pressure, the film consists of almost pure perovskite phase and comparatively better electrical characteristics. X-ray reflectometry study indicates very low density of PZT films with an interlayer formed at the interface with Pt. XTEM study throws valuable insight into the nano-scale structure and reveals the presence of nano-porosity along the interface as well as within the film microstructure. This has been attributed to the observed interface roughness, reduced density, tensile residual stress as well as the poor ferroelectric properties encountered.

Does cholesterol preferentially pack in lipid domains with saturated sphingomyelin over phosphatidylcholine? A comprehensive monolayer study combined with grazing incidence X-ray diffraction and Brewster angle microscopy experiments

In this work, the Langmuir monolayers were used as a model for the analysis of the influence of cholesterol on 1,2-distearoyl-sn-glycero-3-phosphocholine – DSPC and stearoyl sphingomyelin – SSM, as well as their equimolar mixture. The aim of these studies was to compare the affinity of cholesterol to sphingomyelin and phosphatidylcholine and discuss the effectiveness of cholesterol packing with these phospholipids. The experiments involved the registration of the surface pressure–area isotherms combined with the application of Brewster angle microscopy (BAM) images and grazing incidence X-ray diffraction methods. We have performed a thorough analysis of the properties of both one-component DSPC and SSM films as well as their 1:1 mixture. Next, the effect of cholesterol on these systems was verified based on the results for 2:1 SSM/Chol, 2:1 DSPC/Chol, and 1:1:1 DSPC/SSM/Chol mixtures. It was found that both phospholipids form highly condensed monolayers, however, they differ in the orientation of acyl chains, namely the acyl chains are more tilted in DSPC film as compared to SSM monolayer as well as DSPC/SSM mixture. Furthermore, the area contraction provoked by the addition of cholesterol was found to be more pronounced for DSPC monolayer than in DSPC/SSM and SSM films. However, all the collected results allow one to postulate that the ability of cholesterol to form ordered domains with DSPC and SSM is similar and is predominantly driven by hydrophobic forces between molecules. The differences in the area condensation induced by cholesterol on the studied phospholipids films results from differences in molecular organization of pure phospholipids films rather than specific cholesterol–phospholipid interactions.

Formation of Self-Assembled Organosilicon-Functionalized Quinquethiophene Monolayers by Fast Processing Techniques

Different techniques for a relatively fast self-assembled monolayer film formation such as Langmuir-Blodgett (LB), spin-coating, and dip-coating methods have been compared using chloro[11-(5''''-ethyl-2,2':5',2″:5''',2''':5''',2''''-quinquethiophene-5-yl)undecyl]dimethylsilane as a reactive precursor. It was shown that both spin-coating and LB techniques are very promising methods for preparation of highly ordered monolayer films of organosilicon-functionalized quinquethiophene with vertical orientation of oligothiophene fragments, while dip-coating gives only partial coverage. Optimal conditions for complete filling out the substrate surface by the quinquethiophene-containing monolayer by spin-coating and LB methods have been found. Grazing incidence X-ray diffraction measurements confirmed formation of in-plane crystalline order within the monolayer film. Changes in the layer structure were established by X-ray reflectivity and grazing incidence X-ray diffraction methods.

Induced magnetic anisotropy and strain in permalloy films deposited under magnetic field

Field induced magnetic-anisotropy is a very important but poorly understood property. There have been many hypotheses on the origin of the phenomenon, e.g. strain, atomic pair ordering, etc., but little experimental evidence exist. This study prepares 100nm thick Permalloy films having the field-induced-magnetic-anisotropy and carefully measure strains, i.e. interplanar distance of crystallographic (111) planes in various directions, using high power synchrotron radiation and precise Grazing Incidence X-Ray Diffraction method. The result delineates that the field-induced-magnetic-anisotropy has a strong correlation with the strain-anisotropy in the film.

Structural irradiation damage and recovery in nanometric silicon carbide

Silicon carbide is one of the candidate materials for core components of some nuclear reactor projects (Gen-IV). In order to improve their thermo-mechanical properties, materials with nanometric grain size are considered. For such materials, nearly no data concerning their behaviour under irradiation are available. In this paper, we study the damage and subsequent recovery of a nanostructured 3C–SiC ceramic. Samples were irradiated at room temperature with 4 MeV Au ions and subsequently annealed. Their structural modifications are analysed with a grazing incidence X-ray diffraction method. Results show that these nanoceramic materials present the same damage kinetics during irradiation as conventional micrometric grained SiC, with total amorphisation at the highest fluence. However, while the recrystallisation of a conventional ceramic is expected to occur through an epitaxial recrystallisation from the non-damaged parts of the large grains, the nanometric material is healed only after annealing at 1000 °C through mechanisms that can be attributed to a heterogeneous nucleation and growth of β crystallites in the totally amorphised grains.

X-Ray Measurement of Residual Stress Distribution in Sputtered Cu Thin Films

Three kinds of copper thin films were fabricated by RF-magnetron sputtering. The target power was selected to be 10 and 150 W to change the properties of the films. Thin glass sheet was used as a substrate. For the target power of 150 W, the deposition time was selected to be 7 and 40 min. The thickness was 0.6 μm and 2.9 μm, and the grain size measured was 243 nm and 450 nm, respectively. The grain size of thicker film was larger than that of thinner one. On the other hand, for the target power of 10 W, the thickness and grain size were 2.4 μm and 54 nm, respectively. The grain size depends on the target power. The residual stress distribution in the films was measured by X-ray method. Several methods such as the grazing incidence X-ray diffraction method, the constant penetration depth method and the conventional sin2ψ method were adopted. The measured weighted average stress increased with increasing depth. After taking the maximum value at about 0.3 μm from the surface, the value decreased with increasing depth. The stress distribution near the surface in the films deposited at 150 W was almost identical irrespective of thickness. On the other hand, for the target power of 10 W, the stress distribution shifted to compression side. The reason could be explained by the effect of the thermal residual stress. The real stress distribution was estimated by using the optimization technique. The stress took the maximum value at 0.5 μm from the surface, and was compressive near the substrate. .

MgxC60 Fabricated by Using Mg:C60 Co-Evaporation Method for Carrier Doping

Mg:C60 co-evaporation method has been performed to obtain fulleride of MgxC60 thin films for carrier doping. Atomic concentration of the film has been examined by x-ray photoelectron spectroscopy to calibrate the composition ratio, and the results indicated that Mg concentration in the film was controlled well. Then, crystal structure of the Mg:C60 mixing film has been examined by using grazing incidence x-ray diffraction method. The diffraction patterns suggested that these films were microcrystalline MgxC60. Conductivity of the mixing films was increased as composition ratio of Mg increasing. It indicates that Mg atoms acted as carrier dopant.