X-ray Pole Figure Research Articles

Superplastic Flow at Elevated Temperatures in As-Rolled AZ91 Sheet

An alternative processing method for superplastic magnesium alloys has been studied on the form of sheet of Mg–9Al–1Zn (AZ91) via large strain by ingot metallurgy with an isothermal-rolling. Constant initial strain rate tensile tests have been conducted at elevated temperatures for AZ91 sheets as rolled with reduction in area of 90%.The values of total elongation exceeded over 50% at all strain rates and at all testing temperatures except 673 K, and the maximum total elongation exhibited 210%. The total elongation had a tendency to increase at low temperature side.The strain rate sensitivity, m-values, exceeded over 0.5 at strain rates from 1.0×10−4 to 2.5×10−4 s−1. The values of flow stress were lower than those of completely recrystallized AZ91 and did not depend so much on the tensile temperatures from 573 to 648 K at high strain rates.The activation energy required for superplastic flow in the high-m-deformation was calculated to be 80–83 kJ·mol−1. This value was close to the grain boundary self-diffusion energy of Mg.Anisotropic textures were no seen in X-ray (0002) pole figure analysis (XPFA) by Schulz's reflection method. It was suggested that the stress concentrations through grain boundaries or in grains could be relaxed during superplastic deformation process and the superplastic flow was more easily associated with boundary diffusion.

Crystallographic Texture and Whiskers in Electrodeposited Tin Films

Electron back scatter diffraction (EBSD) analysis was used to determine texture for electrodeposited tin films, and the results were compared to standard X-ray "times random" and full pole figure texture analysis. The data showed that EBSD and X-ray texture results differed as to primary and secondary texture determinations with some degree of correlation between texture determinations when primary/secondary/tertiary calculations were disregarded. It is these authors' opinion that film texture cannot be accurately determined using "times random" X-ray diffraction (XRD) techniques, and that there is considerable room for error with X-ray pole figure analyses. These data must be considered preliminary due to the small sample size, but these results indicate that electroplaters may have better control over as-deposited tin film texture than is currently believed, and that there is a relationship between as-deposited texture and film stress

Low-Temperature Growth of GaN film by Near-Atmospheric Plasma-Assisted Chemical Vapor Deposition

A GaN thin film was fabricated by near-atmospheric plasma-assisted chemical vapor deposition. Pure nitrogen plasma can be generated stably using an alternating pulsed voltage system that applies an alternating pulsed voltage between two parallel plate electrodes. The excited nitrogen species correspond to the N2 second positive system. Ionic molecular species, which cause film damage, were not observed by optical emission spectrum analysis. Using this plasma as a nitrogen source, metalorganic chemical vapor deposition of GaN thin mm was carried out under a nitrogen partial pressure of 40 kPa and substrate temperature of 400oC. The quality of the GaN thin film was analyzed by means of 2-dimensional X-ray diffraction and X-ray pole figure measurement. The measurements revealed that the film was epitaxial with a 30o rotation of the unit cell with respect to (0001) sapphire in the (0001) basal plane.

Texture Evolution in Ni Substrate Prepared by Powder Metallurgy and Casting Methods

Cube textured Ni substrate were fabricated for YBCO coated conductors from the initial specimens prepared by powder metallurgy (P/M) and casting and the effects of annealing temperature and reduction ratio on texture formation and microstructural evolutio were evaluated. The initial specimens were rolled by 98.6% and 99.2% reduction ratio and then annealed in the temperature range of 600°C to 1200°C. The microstructure and texture were evaluated by optical microscopy and X-ray pole-figure analysis. We observed that microstructure of the initial specimen varied with preparation methods.Texture analysis indicated that a strong cube texture formed for substrate made by P/M, and the degree of texture did not significantly vary with annealing temperature of 600°C~1100°C. On the other hand, the texture of substrate made by casting was more dependent on the annealing temperature and twin texture ({221}<221>) and several minor texture components started to form at 1000°C. In addition, the texture of substrate made by P/M was significantly dependent on the reduction ratio.

Surface pole figures by reflection high-energy electron diffraction

The authors demonstrated that it is possible to construct a reflection high-energy electron diffraction (RHEED) pole figure of a polycrystalline film by recording multiple RHEED patterns as they rotate the substrate around the surface normal. Since electrons have limited penetration depth, the pole figure constructed is a surface pole figure. It is in contrast with the conventional x-ray pole figure which gives an average texture information of the entire film. Surface texture change, particularly the evolution of multiple preferred orientations, in polycrystalline Ru films grown by oblique angle vapor deposition has been observed using this RHEED surface pole figure technique.

Microstructure and texture evolution of Ti-Nb-Si based alloys for biomedical applications

Microstructure and texture of Ti-Nb-Si based alloys, prepared by water quenching from β-phase field, cold rolling and recrystallization heat treatment followed by water quenching, were investigated in terms of optical microstructure and analysis of X-ray pole figure result. In as-quenched sample, relatively random distribution of pole figure was detected without showing a specific texture component. In as-cold rolled sample, however, it is found well-developed several texture components consisting of rotated cube, α-fiber and γ-fiber texture components which are frequently observed in bcc-structured metals and alloys were found. Therefore, texture components developed in the present alloys are closely related to the deformation of β-phase even though small amount of α″ phase co-exist in the microstructure. In recrystallized sample, α-fiber texture component is weakly detected while the other texture components, rotated cube and γ-fiber components, appears to be relatively unchanged. No additional texture components were detected besides those texture components observed in the cold rolled samples.

Epitaxial growth of (1 1 1)ZrN thin films on (1 1 1)Si substrate by reactive sputtering and their surface morphologies

We have investigated the epitaxial growth of (1 1 1)ZrN films on (1 1 1)Si substrate at a relatively low temperature using an ultrahigh vacuum DC magnetron sputtering system. The film quality obtained and the epitaxial relationship were evaluated on the basis of analyses of X-ray diffraction (XRD) patterns, X-ray pole figures, and grazing incidence angle X-ray reflectivity (GIXR), transmission electron microscopy (TEM) and atomic force microscopy (AFM) results. It was found that (1 1 1)ZrN films were grown epitaxially on (1 1 1)Si at a substrate temperature of 500 ∘ C with the directional relationship ZrN(1 1 1)[1 1 0] ∥ Si(1 1 1)[1 1 0]. GIXR and AFM results also revealed that the epitaxial (1 1 1)ZrN film has a high film density comparable to that of bulk ZrN and a fairly flat surface morphology with an average surface roughness of approximately 0.25 nm.

A Structural Study of Electrodeposited Fe on n-GaAs ( 001 )

The microstructure of Fe films electrodeposited onto from and electrolytes was examined by X-ray and electron diffraction. Symmetrical X-Ray diffraction from films deposited from chloride solutions indicates a dominant (001) texture with the presence of additional minority orientations. In contrast, deposition from an ammonium sulfate electrolyte yields films that only exhibit (001) scattering in the geometry. Transmission electron microscopy (TEM) cross-sectional images of films grown in chloride solutions reveal intermittent cube-on-cube epitaxy that is also evident in plan view TEM dark field images. Interestingly, X-ray pole figure measurements for all specimens examined reveal an additional (221) orientation that is undetectable by symmetric diffraction. The (221) oriented material most likely derives from twinning of (001) oriented grains during growth.

Epitaxial Growth of Full-Heusler Alloy Co$_2$MnSi Thin Films on MgO-Buffered MgO Substrates

Full-Heusler alloy Co2MnSi (CMS) thin films were epitaxially grown on MgO-buffered MgO substrates through magnetron sputtering. The films were deposited at room temperature and subsequently annealed in situ at 600degC. X-ray pole figure measurements of the annealed films showed 111 peaks with fourfold symmetry, providing direct evidence that these films were epitaxial and crystallized in the L21 structure. The annealed films had sufficiently flat surface morphologies with root-mean-square roughness of about 0.22 nm at a film thickness of 50 nm. The saturation magnetization of the annealed films was 4.5muB/f.u. at 10 K, corresponding to about 90% of the Slater-Pauling value for CMS

Crystal evaluation of spherical silicon produced by dropping method and their solar cell performance

The characterization of silicon spheres 1 mm in diameter, which were produced by a dropping method and solar cell performance using spheres are reported. Scanning electron microscopy observations of the Si spheres after Dash etching and X-ray pole figures indicate that the spherical Si has many defects and crystal grains. Systematic study of the crystal growth temperature and the atmosphere in the dropping area yields improvements in the crystallinity as well as a decrease in the concentrations of oxygen and carbon. Moreover, the spherical Si solar cell performance improved because these impurities are the prime factor for recombination centers.

Room temperature epitaxial growth of TiN on SiC

Epitaxial growth of a titanium nitride (TiN) on (6H)-SiC (0001) is achieved at room temperature by means of direct current magnetron sputtering. The epitaxial relationship is established by X-ray pole figure and Φ-scan. Cross-sectional transmission electron microscopy and pole figure analysis show that the orientation relationship is ( 111 ) TiN ‖ ( 0001 ) SiC [ 0 1 ¯ 1 ] TiN ‖ [ 1 2 ¯ 10 ] SiC , It is different from that on sapphire, “ ( 111 ) TiN ‖ ( 0001 ) Al 2 O 3 [ 10 1 ¯ ] TiN ‖ [ 10 1 ¯ 0 ] Al 2 O 3 ” , in spite of the same crystal structure of substrate surfaces. Different lattice mismatch is a plausible explanation.

Reaction of thin Ni films with Ge: Phase formation and texture

The solid-state reaction between a 30-nm-thick Ni film and Ge substrates was investigated using in situ x-ray diffraction, diffuse light scattering, and four-point probe electrical measurements. Our results reveal that Ni5Ge3 and NiGe appear consecutively on Ge(111) while they grow simultaneously on amorphous Ge(α-Ge) and Ge(001). Furthermore, phase formation temperatures depend strongly on the nature of the substrate being the lowest on α-Ge and the highest on Ge(111). X-ray pole figure measurements of the NiGe phase obtained from the reaction with an amorphous substrate indicate a completely random texture while several epitaxial and axiotaxial texture components are observed on both Ge(001) and Ge(111). The texturing for the NiGe film on Ge(111), which showed a sequential phase formation, is an order of magnitude more pronounced than for the film on Ge(001) which showed a simultaneous growth.

Development of textured substrates with high strength and weak magnetism

Ni-clad substrates for HTS coated conductors have been developed to enhance their mechanical strength and to reduce their magnetization. The Ni-clad substrate has a sandwich structure, which comprises two pure Ni layers at the top and bottom sides and a Ni–Mo alloy layer at the center.The textured Ni-clad substrate shows a 0.2% proof stress of 1.1GPa, which is 25 times higher than that of the textured pure Ni substrate. The saturated magnetization is about half that of pure Ni substrate, which reduces the magnetic loss of the substrate remarkably. In order to evaluate bi-axially textured growth of the buffer layers on the substrate, a CeO2 buffer layer was deposited by electron-beam evaporation. The X-ray diffraction and pole figure analysis of the CeO2 buffer layer indicate that the buffer layer has the {200}〈220〉 cube orientation.A 40m-long Ni-clad substrate has been successfully fabricated to demonstrate the mass-productivity. The 40m-substrate exhibits that the orientation is a good alignment and the quality is homogeneous over the full length.The Ni-clad substrate is expected to be one of the useful substrates for HTS coated conductors.

Polycrystal elastic constants for triclinic crystal and physical symmetry

The problem of obtaining the Voigt average for the elastic stiffnesses with texture-describing weight functions has been solved for triclinic crystal and physical symmetries. The average is obtained by expanding theTijklmnpq, which relate the elastic stiffnesses in the rotated reference frame, c^{\,\prime}_{ijkl}, to those of the principal elastic stiffnesses,cmnpq, in generalized spherical harmonics, multiplying by the orientation distribution function and integrating over all orientations. The condition imposed to assure a unique expansion results in the absence of terms with oddL, so that the results are completely determinable from conventional X-ray pole figures. This is the most general case, from which all higher-symmetry solutions may be obtained by application of symmetry operations. The Reuss average for elastic compliances may be obtained in a similar fashion.

Effects of short time heat treatment on superelastic properties of a Ti–Nb–Al biomedical shape memory alloy

The effect of short time heat treatment on microstructure, texture formation and anisotropy on superelastic properties was investigated for a Ti–24Nb–3Al (at.%) alloy, which is a Ni-free and β-titanium based biomedical shape memory alloy. An ingot was made by Ar-arc melting, homogenized at 1273 K for 7.2 ks, and then cold rolled with 99% reduction in thickness. Then, the alloy was heat-treated at 973, 1123 and 1273 K for 60, 120, 180 and 300 s, etc. X-ray diffraction analysis, X-ray pole figure measurement and scanning electron microscopy (SEM) combined with the recording of electron backscattering patterns (EBSP), were made for alloy characterization. Cyclic loading–unloading tensile test was performed to evaluate superelasticity for the alloy heat-treated at 1123 K for 120 s. It was found that 〈1 1 0〉 β{0 0 1} β-type deformation texture, which is developed by cold rolling, still appears after the heat treatment at 973 K for 300 s. On the other hand, it was also found that {1 1 2} β〈1 1 0〉 β-type recrystallization texture appears when heat-treated at 1123 K for 180 s and 1273 K at 60 s. Only when heat-treated at 1123 K for 120 s, SEM–EBSP revealed that the alloy contains both deformation texture with a grain size of 0.5 μm in diameter and recrystallization texture with a grain size of 20 μm. By tensile tests, the alloy with such bimodal texture exhibits more isotropic superelastic property of a 4% in all tensile directions than fully recrystallized and cold rolled alloys.

Highly textured Pb(Zr0.3Ti0.7)O3 thin films on GaN/sapphire by metalorganic chemical vapor deposition

Highly (111) textured Pb(Zr0.3Ti0.7)O3 (PZT 30/70) films were deposited on (0001) GaN/sapphire substrates using liquid-source metalorganic chemical vapor deposition (MOCVD) technique at 520 °C and 80 nm/min. The crystallinity of as-deposited PZT films and the structure of PZT/GaN interface were evaluated by x-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM), respectively. Mitigated by geometric epitaxy and strain energy minimization, the orientation relationships of PZT on epi-GaN, determined using x-ray pole figure and selected area diffraction pattern, were as follows: out-of-plane alignment of [111] PZT//[0001] GaN, and orthogonal in-plane alignments of [112] PZT//[1100] GaN (zone axes) and [110] PZT//[1120] GaN. The nanochemistry of the PZT (150nm)/GaN interface, studied using analytical TEM, indicated a chemically sharp interface with interdiffusion limited to a region below 5 nm. The properties of as-deposited PZT on GaN by MOCVD are briefly compared with PZT by sol-gel processing, radio-frequency sputtering, and pulsed laser deposition.

Development of cube textured Ni–5 at.%W alloy substrates for coated conductor application using a melting process

Biaxially textured Ni–5 at.%W substrates have been prepared by cold rolling, followed by three different annealing routes. In this paper, the processes of melting Ni and W metals, flat rolling, various annealing methods are described in detail. The Ni–5 at.%W tapes annealed under either high vacuum or flowing Ar (7% H 2) gas were characterized by X-ray pole figures, ODF, EBSD as well as AFM analysis. The texture analysis indicated that as fabricated tapes have a sharp cube texture formed after annealing at a wide temperature range of 800–1100 °C. The high quality of cube orientation on tapes was obtained after a two-step annealing (TSA), where the percentage of the cube texture component was as high as 93.5% within a misorientation angle smaller than 8° from EBSD analysis. Furthermore, it was also observed that the number of twin boundaries in this tape decreased with respect to that of tapes annealed both in vacuum and one-step gas annealing. From AFM on 1 μm 2 areas, it was concluded that the roughness (RMS) on the tape surface reached 0.98 nm.

Effect of substrate’s nature on the growth of HgBCCO thin films

The synthesis of HgBCCO films by spray pyrolysis on single crystals is investigated. It is shown that in conditions where the precursor is expected to give Hg-1223, Hg-1212 grows on LaAlO 3 (0 0 1) while Hg-1223 grows on MgO (0 0 1). The samples are analysed by X-ray pole figures, SEM and critical current measurements. Both samples were superconducting but the sample on MgO had a negligible I c while 17 A was measured on LAO at 77 K (sf). These differences are analysed in terms of texture and microstructure and some conclusions concerning the growth are drawn. On LAO, the nucleation is probably epitaxial and the anisotropy of the growth inhibits the transformation into Hg-1223 while some interfacial contribution expected to occur on MgO makes this transformation easier.

Crystal Characterization of Spherical Silicon Solar Cell by X-ray Diffraction

We have investigated the crystal quality of spherical Si solar cells by X-ray diffraction. A Si sphere with a diameter of 1 mm was fabricated by a dropping method. X-ray pole figure measurements confirmed that the Si sphere includes twin crystals. The spherical Si solar cells were fabricated using Si spheres. The spherical Si solar cells consisting of almost the same number of crystal grains exhibited various performance characteristics, because no clear correlation between the X-ray pole figure measurements indicating the grain number and the solar cell performance characteristics was confirmed. An X-ray rocking curve and a Dash etching method for the spherical Si solar cells indicated that the short-circuit current density and open-circuit voltage of the solar cells depend on the crystallinity of intragrains.

Structural and magnetic properties of epitaxially grown full-Heusler alloy Co2MnGe thin films deposited using magnetron sputtering

Full-Heusler alloy Co2MnGe thin films were epitaxially grown on MgO (001) substrates using magnetron sputtering. The films were deposited at room temperature and subsequently annealed in situ at temperatures ranging from 400to600°C. X-ray pole figure measurements for the annealed films showed (111) peaks with fourfold symmetry, which gives direct evidence that these films are epitaxial and crystallized in the L21 structure. Furthermore, cross-sectional transmission electron microscope images of a fabricated film indicated that it is single crystalline. The annealed films had sufficiently flat surface morphologies with roughnesses of about 0.26nm rms at film thicknesses of 45nm. The saturation magnetization of the annealed films was 4.49μB∕f.u. at 10K, corresponding to about 90% of the Slater–Pauling value for Co2MnGe.