Bragg-Brentano X-ray Diffraction Research Articles

Structure and Phase State of Ti49.4Ni50.6 (at%) Hydrogenated in Normal Saline.

The paper analyzes the surface structure and phase state of Ti49.4Ni50.6 (at%) hydrogenated at 295 K in normal saline (0.9% NaCl aqueous solution with pH = 5.7) at 20 A/m2 for 0.5–6 h. The analysis shows that the average hydrogen concentration in the alloy increases with the hydrogenation time tH as follows: slowly to 50 ppm at tH = 0.5–1.5 h, steeply to 150 ppm at tH = 1.2–2 h, and linearly to 300 ppm at tH = 2–6 h. According to Bragg–Brentano X-ray diffraction data (θ–2 θ, 2 θ ≤ 50°, CoKα radiation), the alloy in its scanned surface layer of thickness ~5.6 µm reveals a TiNiHx phase with x = 0.64 and x = 0.54 after hydrogenation for 4 and 6 h, respectively. The structure of this phase is identifiable as an orthorhombic hydride similar to β1–TiFeH0.94 (space group Pmcm), rather than as a tetragonal TiNiHx hydride with x = 0.30–1.0 (space group I4/mmm). Time curves are presented to trace the lattice parameters and volume change during the formation of such an orthorhombic phase from the initial cubic B2 phase in Ti49.4Ni50.6 (at%).

Application of X-rays Diffraction for Identifying Thin Oxide Surface Layers on Zinc Coatings

Structural characterization of compound material coatings is usually achieved using time-consuming and destructive techniques such as optical and electrical microscopy, which require the use of grinding processes not always compatible with the material. This paper reports on the effective use of a theoretical model based on X-ray diffraction to calculate the thickness and composition of thin oxide films formed on the surface of zinc coatings. Zinc coatings are widely used in industrial application as protective layers against the atmospheric corrosion of steel substrates. The thickness of single- and multi-layer coatings is estimated using grazing incidence X-ray diffraction and various incidence angles. The coatings were grown using hot-dip, pack cementation and thermal spray techniques, and their experimental characteristics were compared to the theoretically predicted values of thickness and composition. The results indicate the formation of a thin zinc oxide film on top of each coating, which acts as an isolation layer and protects the surface of the sample against the environmental corrosion. Finally, the penetration depth of the X-rays into the zinc-based coatings for grazing incidence and Bragg–Brentano X-ray diffraction geometries were calculated using theoretical equations and experimentally confirmed.

Determining intrinsic stress and strain state of fibre-textured thin films by X-ray diffraction measurements using combined asymmetrical and Bragg-Brentano configurations

Measuring intrinsic macro stresses in fibre-textured thin films have always been challenging. Due to the nature of preferential orientation in these films, only d-spacings aligned with the film surface are observable in Bragg-Brentano X-ray diffraction scans, and to collect sufficient diffraction data needed for the stress calculation, a sample stage with tilt capabilities is essentially required. In this article, a new method is developed to lift this requirement. Based on the thin film crystal structure, an incident angle for asymmetrical XRD configuration is calculated to reveal tilted planes belonging to the same group of crystallites which are the textured majority. Measurement of d-spacing for this angle of incidence in combination with the Bragg-Brentano configuration is shown to successfully extract stress-free lattice parameter and the internal stress of the cubic metallic thin film. This method can also be adapted to determine stress and strain in polycrystalline thin films.

Structural and mechanical characterization of nanostructured titanium oxide thin films deposited by filtered cathodic vacuum arc

Titanium oxides are interesting materials, because they can be used for photocatalytic, optical and gas sensing purposes. In a variety of applications, the present phases and film structure have an influence on the effectiveness of the coating function: for this reason, deposition parameter control plays a fundamental role in the formation of coatings with the wished features. In this work, titanium oxide films are deposited by filtered cathodic vacuum arc (FCVA) operated in a pulse mode. FCVA is a versatile deposition system appreciated both in research and industry for its high deposition rate, for the possibility to control the ion energy and for the production of nearly fully ionized plasma. A pure titanium cathode is used as ion source, and depositions are carried out in an oxygen reactive atmosphere.The effects of substrate temperature and substrate bias on film properties, structure and composition are investigated. Bragg–Brentano X-ray diffraction, and electron and atomic force microscopy are used to assess the deposited film structure, while nanoindentation is used to study film mechanical properties. Phases, roughness, hardness and reduced Young's modulus are studied as a function of the deposition parameters. Correlation between deposition conditions and structure of synthesized films is discussed, taking into account the features of plasma produced by a filtered cathodic arc system.

Characterisation of melt spun Ni-Ti shape memory Ribbons’ microstructure

NiTi alloys are the most technologically important medical Shape Memory Alloys in a wide range of applications used in Orthopaedics, Neurology, Cardiology and interventional Radiology as guide-wires, self-expandable stents, stent grafts, inferior vena cava filters and clinical instruments. This paper discusses the use of rapid solidification by the melt spinning method for the preparation of thin NiTi ribbons for medical uses. Generally, the application of rapid solidification via melt-spinning can change the microstructure drastically, which improves ductility and shape memory characteristics and leads to samples with small dimensions. As the increase in the wheel speed led to a reduced ribbon thickness, the cooling rate increased and, therefore, the martensitic substructure became finer. Furthermore, no transition from the crystalline phase to the amorphous phase was obtained by increasing the cooling rate, even at a wheel speed of 30 m/s. Specimens for our metallographic investigation were cut from the longitudinal cross sections of melt-spun ribbons. Conventional TEM studies were carried out with an acceleration voltage of 120 kV. Additionally, the chemical composition of the samples was examined with a TEM equipped with an EDX analyser. The crystallographic structure was determined using Bragg-Brentano x-ray diffraction with Cu-Kα radiation at room temperature.

Determining the C60 molecular arrangement in thin films by means of X-ray diffraction

The electrical and optical properties of molecular thin films are widely used, for instance in organic electronics, and depend strongly on the molecular arrangement of the organic layers. It is shown here how atomic structural information can be obtained from molecular films without further knowledge of the single-crystal structure. C60 fullerene was chosen as a representative test material. A 250 nm C60 film was investigated by grazing-incidence X-ray diffraction and the data compared with a Bragg–Brentano X-ray diffraction measurement of the corresponding C60 powder. The diffraction patterns of both powder and film were used to calculate the pair distribution function (PDF), which allowed an investigation of the short-range order of the structures. With the help of the PDF, a structure model for the C60 molecular arrangement was determined for both C60 powder and thin film. The results agree very well with a classical whole-pattern fitting approach for the C60 diffraction patterns.

Titanium oxide thin film deposition by pulsed arc vacuum plasma

The experimental study of effects of deposition conditions and plasma parameters on the structure of titanium oxide films is presented. The films are deposited by reactive deposition from a plasma generated by a pulsed cathodic vacuum arc source. The effects of deposition time and substrate bias voltage are studied, the films being deposited at different substrate temperatures. Bragg-Brentano X-ray diffraction and electron microscopy were used to investigate the structure of deposited films. Correlation between plasma parameters, deposition conditions and structure of synthesized films are established.

Towards particle size regulation of chemically deposited lead sulfide (PbS)

Powders and solid films of lead sulfides (PbS) were produced by chemical bath deposition from thiourea aqueous solutions at a temperature of 325 K. By a Rietveld-like analysis of the X-ray spectra, it was shown that nanocrystalline PbS has the same rock salt structure B1 (space group Fm-3m) as coarse grained or single crystalline PbS. Nevertheless, this B1 structure is a very distorted structure with root mean square displacements up to 0.011 nm and with a microstrain up to 0.3%. The particle sizes in the PbS powders and films measured by scanning electron microscopy (SEM) are found to be in agreement with those determined by Bragg–Brentano X-ray diffraction (XRD) on powders and by glancing incident diffraction (GID) on films. It was found that by changing the chemical affinity in the range from 31.4 to 38.7 kJ/mol, it is possible to regulate the particle size of the chemically deposited sulfide powders from 100 to 300 nm.

Influence of the substrate bias on the size and thermal stability of grains in magnetron-sputtered nanocrystalline Ag films

The nanostructural evolution during heat treatments of direct-current magnetron-sputtered Ag films, deposited at room temperature at different substrate bias voltages, was experimentally studied. A growth chamber equipped with a magnetron and Kapton windows for in-situ x-ray diffraction was mounted on a six-circle goniometer at a synchrotron beam line. Bragg–Brentano x-ray diffraction was used to monitor the (111) Bragg peak during thermal annealing of the Ag films. In addition, to investigate the 〈111〉 fiber texture, one-dimensional pole figures were measured ex situ. The thermal stability of the nanostructure was sensitively dependent on the substrate bias voltage. Increasing the bias voltage resulted in significantly lower rates of grain growth, which we ascribe mainly to the formation of Ar bubbles. Furthermore, the grain size in the as-deposited films decreased with increasing bias voltage while the width of the one-dimensional pole figures increased.

On the dependence on bias voltage of the structural evolution of magnetron- sputtered nanocrystalline Cu films during thermal annealing

The nanostructural evolution during heat treatments of DC magnetron-sputtered Cu films deposited at different substrate bias voltages was experimentally studied. A growth chamber equipped with two magnetrons and Kapton windows for in-situ X-ray diffraction was mounted on a six-circle goniometer at a synchrotron beam line. Using Bragg–Brentano X-ray diffraction, the grain size, the texture, and the lattice constant were monitored during thermal annealing. Increasing the substrate bias voltage, the grain growth rate lowered, and the change in texture with time became smaller due to a decrease in the defect concentration. Furthermore, the grain size in the as-deposited films decreased with increasing bias voltage. The activation energy for grain growth was, within experimental errors, the same in all the films.

On the development of texture during growth of magnetron-sputtered CrN

During growth of CrN films deposited by reactive magnetron sputtering, the development of the microstructure, especially the texture, was studied. By ex-situ Bragg–Brentano X-ray diffraction measurements, the texture, the grain size and the microstrain were measured as a function of film thickness. In addition, in-situ Bragg–Brentano X-ray diffraction and reflection measurements were carried out with synchrotron radiation, including measurements where the dynamic development of the microstructure was followed in real-time. Below a transition deposition temperature of approximately 550 °C, it was found that the 〈0 0 2〉 preferred orientation dominated, while a mixture of 〈1 1 1〉 and 〈0 0 2〉 preferred orientations was found above the transition temperature. The development of texture with film thickness was controlled by a recrystallization mechanism. With increasing film thickness, the grain size increased while the microstrain decreased. The real-time measurements with synchrotron radiation revealed that several different dynamic processes took place both during and after depositions. After a long-time interruption of the growth, major changes in the texture were observed.

Crystallographic texture of EB-PVD TBCs deposited on stationary flat surfaces in a multiple ingot coating chamber as a function of chamber position

The crystallographic texture of EB-PVD TBCs has been experimentally determined by pole figure analysis and X-ray diffraction. It was found that the TBC coating deposited on a stationary flat surface directly above an ingot or between the two ingots and off center exhibited single crystal texture. Coatings deposited at the far corners of the coating chamber revealed a fiber texture with 〈111〉 column growth direction. The Bragg–Brentano X-ray diffraction analysis revealed a variety of textures (i.e. crystallographic planes that are parallel to the substrate surface) with the most predominant planes being the (220), (311), (420) and (620).

Electrodes and Barriers for Dram and Feram: Processing, Integration, and Fundamentals

AbstractMaterials requirements for electrodes and barriers in high density dynamic random access memory (DRAM) and ferroelectric random access memory (FERAM) are reviewed, and some approaches to barrier materials and device geometries are described. Electrode/barrier topics covered in more detail include Pt reactivity with Si-containing barriers and dielectric overlayers, the application of a Bragg-Brentano x-ray diffraction technique to quantitatively probe Pt and Ir electrode morphology and thickness changes during ferroelectric processing, the stability of metal oxide electrode materials in reducing ambients, electrode patterning techniques (including Pt electroplating), and electrical properties of 3-D capacitors in 256k arrays as a function of top electrode annealing treatments.

Characterisation of ZnS:Mn thin films by Rietveld refinement of Bragg–Brentano X-ray diffraction patterns

In this work, we investigate ZnS:Mn polycrystalline thin films deposited onto glass substrates coated by tin or bismuth buffer layers, by using X-ray diffraction in the conventional Bragg–Brentano geometry. The ZnS:Mn thin films were deposited via radio frequency magnetron sputtering from a ZnS:Mn target (0.1% atomic Mn) and the buffer layers by thermal vacuum evaporation. A suitable algorithm were introduced in the Rietveld routine for powder diffraction data in order to model the X-ray diffraction patterns of the multilayers. The experimental results reveal that the microstructure and the crystalline phase of the ZnS films depend decisively on the structural and microstructural properties of the buffer layers.

Correlation between titania film structure and near ultraviolet optical absorption

Titania is a material with structural flexibility, and as a result, readily forms both crystalline polymorphs and an amorphous structure in thin films grown near room temperature. The goal of this study is to correlate fundamental optical absorption edge characteristics with the phase constituency of titania films. To that end, films with coexistent rutile, anatase, and amorphous constituents were sputter deposited onto fused silica and 〈111〉-Si substrates. The films were then subjected to cyclic annealing in air at moderate temperature (700 and 1000 °C) to affect phase changes. Bragg–Brentano x-ray diffraction was used for phase identification and near ultraviolet-visible transmission and reflection spectrophotometry was used to determine the optical absorption coefficient at the onset of interband transitions. The optical absorption coefficient was modeled within the framework of the coherent potential approximation (CPA), with Gaussian site disorder introduced into the valence and conduction bands of a perfect virtual crystal. Two parameters of the disordered crystal were defined: the optical band gap, Ex, and the slope of absorption edge, Eo. The results are discussed in terms of two extreme cases: (1) film states containing a large rutile volume fraction (0.70–1) share a rutile virtual crystal, with Eg=3.22 eV. Data for these states was combined with single crystal data to develop an expression interrelating Eg, Ex, and Eo. This expression is applicable to any structure with a rutile virtual crystal. The relationship between structural disorder (i.e., the volume fraction of amorphous material) and electronic disorder (i.e., Eo), is quantitatively consistent with the CPA model. (2) Film states containing a small rutile volume fraction (0.02–0.17), and hence a large anatase+amorphous component, share a nonrutile virtual crystal, with Eg=3.41 eV. The effect of increasing the structural disorder (i.e., the rutile volume fraction), in these states is to shift Ex to lower values, which is qualitatively consistent with the CPA model. Furthermore, anatase and amorphous components can be modeled using the same nonrutile virtual crystal, indicating these structures have a common short-range order in the sputter deposited films of this study.

Highly Oriented Nb-Doped Lead Titanate Thin Films by Reactive Sputtering: Fabrication and Structure Analyses

Highly oriented lead titanate thin films have been deposited on bare (100)MgO substrates and on (100)Pt/(100)MgO substrates by reactive sputtering. By adding metallic niobium chips to the target, Nb-doped PbTiO3 films could be obtained as well. The variation in the orientation of PbTiO3 films due to the deposition conditions is described in detail. Due to the highly oriented nature of the films, two types of X-ray diffraction methods were used to evaluate the effect of Nb doping on the tetragonality ratio c/a: one was the conventional θ–2θ Bragg-Brentano X-ray diffraction method (XRD), the other was the in-plane energy-dispersive total reflection X-ray diffraction method (ED-TXRD), which could provide the lattice vectors perpendicular (c axis) and parallel (a axis) to the substrate, respectively. Furthermore, the epitaxy of the deposited PbTiO3 films in relation to the (100)-cut MgO single crystal substrate could be confirmed using ED-TXRD.

Structural perfection of (001) CeO2 thin films on (11_02) sapphire

Large-area (001) oriented epitaxial CeO2 films with extremely high crystalline perfection characterized by x-ray diffraction rocking curves of the (002) CeO2 reflection with a full width at half maximum (FWHM) Δω⩽0.013° and thickness dependent oscillations in the Bragg-Brentano x-ray diffraction spectra were deposited via rf-magnetron sputtering on (11_02) sapphire. Pole figure measurements of the space symmetry confirmed that the examined sharp reflections belong to CeO2 and no other phases like CeAlO3 are present. The improvement of the crystalline quality was obtained by optimization of the high-pressure sputter deposition process and the use of large-area substrates. The [100] CeO2 axis was slightly tilted with respect to the [11_02] sapphire axis by 0.185°. Subsequently sputter-deposited high-Tc YBa2Cu3O7−x thin films revealed structural properties characterized by FWHM <0.06° of the (005) θ-2θ peaks and by FWHM of the (005) peaks rocking curves of Δω=0.3°.

Influence of substrate bias on the microstructure of sputtered Al-Zn alloy coatings

The influence of energetic particle bombardment in the modification of vacuum deposited coatings is reasonably well understood. However, the ion assisted deposition of alloy coatings is considerably more complex, and is often influenced by the re-emission of deposited material. In this work, unbalanced magnetron sputtering is used to study the effect of substrate bias on the composition and microstructure of coatings deposited with ion assistance. The coatings were sputtered from targets of Zn and two Al-Zn alloys onto silicon substrates, over a range of bias voltages. The composition, microstructure, and morphology of the coatings were characterised by energy dispersive X-ray spectrometry, Bragg-Brentano X-ray diffraction, and scanning electron microscopy respectively. The Zn coatings were highly preferred with the close packed plane parallel to the substrate surface. The residual stresses of the deposited films were highly dependent on the substrate bias. The Zn coatings were also affected by resputtering and re-evaporation of the deposited material due to energetic particle bombardment. The microstructures of the Al-Zn alloy coatings were influenced largely by the relatively high T/ T m, which favoured the segregation of Zn and Al into discrete grains. Energetic ion bombardment during the growth of the alloy coatings significantly affected the coating composition by preferential resputtering and/or re-evaporation of Zn. Furthermore, the bias voltage required to reject the Zn completely from the coating varied with its concentration in the target. It is argued that this effect occurs when the Zn re-emission flux is equal to the Zn flux arriving at the substrate, so that only Al is deposited when the bias voltage is sufficiently high.

Growth of MBE-Codeposited IrSi3 on Si(111) and Si(100)

AbstractWe have used Molecular Beam Epitaxy (MBE) to successfully grow films that are predominantly IrSi3 on both Si(111) and Si(100) substrates by codeposition of Si and Ir in a 3:1 ratio. Bragg-Brentano and Seemann-Bohlin x-ray diffraction reveal that polycrystalline IrSi3 films form as low as 450 °C. This is the lowest temperature yet reported for growth of this iridium silicide phase. These x-ray diffraction techniques, along with Transmission Electron Microscope (TEM) diffraction and in situ Low Energy Electron Diffraction (LEED), show that at higher deposition temperatures codeposition can form IrSi3 films on Si(111) that consist predominantly of a single epitaxial growth orientation. Ion beam channeling and x-ray rocking curves show that the epitaxial quality of IrSi3 films deposited on Si(111) is superior to that of IrSi3 films deposited on Si(100). We also present evidence for several new epitaxial IrSi3 growth modes on Si(111) and Si(100).

Structural analysis of ZrN and TiN films prepared by reactive plasma beam deposition

The effect of composition of ZrN and TiN films and deposition temperature on lattice expansion was investigated. ZrN and TiN films containing various at.% of nitrogen were prepared by reactive sputter deposition in a Balzers Sputron plasma beam apparatus. Both ZrN and TiN films were grown at a substrate temperature of 180°C and some of the ZrN films also at substrate temperatures between 400 and 700°C. Interplanar distances and textures were determined using Seeman-Bohlin and Bragg-Brentano X-ray diffraction.