X-ray Pole Figure Research Articles

Laser Dressing of Alumina Grinding Wheels

High-power lasers are being explored as a non-contact-type dressing tool for alumina grinding wheels. The alumina grinding wheel surface underwent melting and/or vaporization on the surface when laser-dressed, forming a modified layer on the surface. Refinement of the grain size took place. The individual particles that formed on the surface had well-defined faceted structures. Microcutting edges were generated on the individual grains and particles, which can act as cutting edges for efficient grinding. The results of x-ray diffraction and pole figure analysis suggested that the formation of these faceted structures was due to the preferential orientation of the grains after dressing.

Heteroepitaxial growth of δ-Bi 2O 3 thin films on CaF 2(1 1 1) by chemical vapour deposition under atmospheric pressure

We have succeeded in achieving the heteroepitaxial growth of a δ-Bi 2O 3 thin film on a CaF 2(1 1 1) substrate by means of chemical vapour deposition under atmospheric pressure. The film grew with a strong (1 1 1) orientation. From X-ray pole figures, it was observed that the δ-Bi 2O 3 film grew on the CaF 2(1 1 1) substrate with 60° rotational in-plane domains. The growth mode was of a 3D island type, and the grain size decreased with increasing oxygen pressure during the δ-Bi 2O 3 film growth, improving the overall surface smoothness.

Imaging of domains in single crystals of BiFeO3-PbTiO3 using various microscopy techniques

Single crystals of BiFeO3-PbTiO3 have been grown from a PbO:Bi2O3 flux by cooling at a rate of 2°C/hour from the melt. Faceted crystals of various morphologies were produced and the size of the crystals ranged from less than 0.5mm to 5mm. Initial measurements were made using the scanning electron microscope (SEM) with energy dispersive X-ray analysis (EDX) semi-quantifying the composition of the crystals as well as electron probe microanalysis (EPMA). Powder X-ray diffraction (XRD) of the crushed and sieved crystals established that the structure was rhombohedral perovskite for the (BiFeO3)0.75-(PbTiO3)0.25 composition and tetragonal perovskite for the (BiFeO3)0.50-(PbTiO3)0.50 composition and mixed phase for the (BiFeO3)0.65-(PbTiO3)0.35 and (BiFeO3)0.70- (PbTiO3)0.30. X-ray pole figures verified that the (BiFeO3)0.75-(PbTiO3)0.25 crystal had grown with a single orientation, the [100] direction. Structures that are believed to be domains have been observed through optical and electron microscopy in backscattered mode. This interim report of on going investigations seeks to eventually confirm the domain structure in the crystals with electron back-scattered diffraction (EBSD).

Fabrication of fully epitaxial magnetic tunnel junctions using cobalt-based full-Heusler alloy thin film and their tunnel magnetoresistance characteristics

Cobalt-based full-Heusler alloy thin films have recently attracted much interest as highly desirable ferromagnetic electrodes for spintronic devices because of the half-metallic ferromagnetic nature theoretically predicted for some of these alloys and because of their high Curie temperatures, which are well above room temperature (RT). In this study, Co-based full-Heusler alloy thin films of Co2Cr0.6Fe0.4Al (CCFA) and Co2MnGe (CMG) were epitaxially grown on MgO-buffered MgO (001) substrates using magnetron sputtering. The films were deposited at RT and subsequently annealed in situ at temperatures ranging from 400 to 600 °C. X-ray pole figure measurements of the CCFA films indicated that these films were epitaxial and crystallized in the B2 structure. X-ray pole figure measurements of the annealed CMG films showed (111) peaks with four-fold symmetry, which provides direct evidence that these films were epitaxial and crystallized in the L21 structure. Furthermore, cross-sectional transmission electron microscope images of a fabricated CMG film indicated that it was single-crystalline. The annealed films of CCFA and CMG had sufficiently flat surface morphologies with roughness of about 0.23 nm rms for 100 nm thick CCFA films and 0.26 nm rms for 45 nm thick CMG films. Using these epitaxially grown thin films, we fabricated fully epitaxial magnetic tunnel junctions (MTJs) consisting of a Co-based full-Heusler thin film of either CCFA or CMG as a lower electrode, a MgO tunnel barrier and a Co50Fe50 (CoFe) upper electrode. All layers were successively deposited in an ultrahigh vacuum chamber through the combined use of magnetron sputtering and electron beam evaporation. Reflection high-energy electron diffraction patterns observed in situ for each layer during preparation clearly indicated that all layers grew epitaxially in both the CCFA/MgO/CoFe and CMG/MgO/CoFe MTJ layer structures. The microfabricated epitaxial CCFA/MgO/CoFe MTJs demonstrated relatively high tunnel magnetoresistance (TMR) ratios, for MTJs using a full-Heusler alloy, of 42% at RT and 74% at 55 K. On the other hand, the microfabricated epitaxial CMG/MgO/CoFe MTJs showed strongly temperature-dependent TMR characteristics with typical TMR ratios of 14% at RT and 70% at 7 K. These results confirm the promise of epitaxial MTJs as a key device structure for clarifying and utilizing the potentially high spin-polarization of Co-based full-Heusler alloy thin films.

Effect of Film Thickness on the Annealing Texture in Sputtered and Electroplated Cu Films

For optimum fabrication and usage of Cu films, an understanding of the relationship between processing and microstructure is required. The existence of twins is another significant factor for texture development in Cu films. Texture character and strength in the Cu film is dependent on the twin boundary development that is a function of processing conditions and film thickness. In this study, determination of grain growth and texture in the sputtered and electroplated Cu films during annealing was performed for films of 100, 480 and 850 nm in thickness deposited on a Ta(25 nm)/Si wafer. The texture was measured by X-ray pole figure. The effect of film thickness on the annealing texture in the sputtered and electroplated Cu films is examined and discussed.

Determination of Biaxial Texture of Thick Film EuBa2Cu3O7-δ Homo-substrate by X-ray Diffraction

We have initially aligned polycrystalline EuBa2Cu3O7-δ (Eu-123) Superconductor using a magnetic force and a mechanical force simultaneously to fabricate biaxially aligned rare earth (RE) substituted Eu-123 thick films as homo-substrates for growth of epitaxial YBa2Cu3O7-δ superconductor thin films. The characterization of such Eu-123 thick films by X-ray pole figure study indicated that the polycrystalline Eu-123 grains having substantial biaxial alignment with their grain [001] axes perpendicular to the surfaces of the thick films and [010] axes parallel to the magnetic field direction in the specimen plane. We were the first to determine the biaxial alignment of Eu-123 homo-substrate by quantitative analysis of X-ray diffraction χ-circle and ϕ-circle scans of (013)/(103) reflections, demonstrating a degree of 33% alignment for both c-axis and a–b axis. The application of the biaxial alignment method to polycrystalline oxides as presented in this paper establishes a new paradigm for the processing of bulk materials.

Correlation between Thermoelectric Properties and Plastic Deformation of p-Type Bi<SUB>0.5</SUB>Sb<SUB>1.5</SUB>Te<SUB>3</SUB> Thermoelectric Materials

A plastic deformation process and ratio study of p-type Bi 0.5 Sb 1.5 Te 3 was performed. The ingots were grown by the Bridgman method. Disks were cut from the ingots and deformed by either cold-pressing or by hot-pressing under pulse current heating. The plastic deformation ratio was controlled from 55 to 90%. The crystal structures of the deformed samples were identified by X-ray diffraction and pole figure analyses. The diffraction patterns indicate that the surfaces and bottoms of the samples were highly oriented in the hexagonal (00-l) plane. Thermoelectric properties change depending on not the plastic deformation ratio but the kind of plastic deformation process. The power factor for hot-press deformed samples exceeded those for the original ingots and cold-press deformed samples. The results suggest that the process of hot-press deformation enhances the thermoelectric properties of p-type Bi 0.5 Sb 1.5 Te 3 .

P-type Bi<sub>0.5</sub>Sb<sub>1.5</sub>Te<sub>3</sub>熱電材料の熱電特性と塑性加工度との相関関係

A plastic deformation process and ratio study of p-type Bi0.5Sb1.5Te3 was performed. The ingots were grown by the Bridgman method. Disks were cut from the ingots and deformed by either cold-pressing or hot-pressing under pulse current heating. The plastic deformation ratio was controlled in the range from 55 to 90%. The crystal structures of the deformed samples were identified by X-ray diffraction and pole figure analyses. The diffraction patterns indicate that the surfaces and bottoms of the samples were highly oriented in the hexagonal (00-l) plane. Thermoelectric properties change depending on not the plastic deformation ratio but the kind of plastic deformation process. The power factor for hot-press deformed samples exceeded those for the original ingots and cold-press deformed samples. The results suggest that the process of hot-press deformation enhances the thermoelectric properties of p-type Bi0.5Sb1.5Te3.

Effect of Ti3Si on Texture in Ti-Nb Based Shape Memory Alloys

AbstractEffect of Ti3Si particles on recrystallization texture of Ti-Nb based superelastic alloys has been investigated using X-ray pole figure measurement and electron backscatter diffraction (EBSD) technique. The alloys used were Ti-24mol%Nb-3mol%Al-Xmol%Si (X=0~0.9, termed XSi) and Ti-24mol%Nb-3mol%Si alloy (termed 3Si). The apparent phase at room temperature was β-phase (bcc). Besides, (Ti, Nb)3Si particles with PTi3 type crystal structure were formed in the alloys with Si content higher than 0.7mol%. After the cold rolling of 99% reduction in thickness, a rolling texture of the β-phase was formed to be mainly {001}β<110>β regardless of the presence of the (Ti, Nb)3Si particles. After the solution treatment at 1273K, a recrystallization texture formed to be {112}β<110>β in all the alloys except for 3Si. The average grain size of the recrystallized alloys was 20~40μm. On the other hand, the solution treated 3Si exhibited the {001}β<110>βn texture and the average grain size of 3μm. It is concluded that the {001}β<110>β texture with fine grains of the solution treated 3Si is obtained by the suppression of grain boundary migration due to the existence of the (Ti, Nb)3Si particles.

Calcium Phosphate Bioceramics with Tailored Crystallographic Texture for Controlling Cell Adhesion

ABSTRACTThe orientation distribution of crystalline grains in calcium phosphate coatings produced by pulsed laser deposition was investigated using an X-ray pole-figure diffractometer. Increased laser energy density of a KrF excimer laser in the 4–7 J/cm2 range leads to the formation of hydroxyapatite grains with the c-axis preferentially aligned perpendicularly to the substrates. This preferred orientation is most pronounced when the plume direction of incidence is normal to the substrate. This crystallographic texture of hydroxyapatite grains in the coatings is associated with the highly directional and energetic nature of the ablation plume. Anisotropic stresses, transport of hydroxyl groups, and dehydroxylation effects during deposition all seem to play important roles in texture development. Studies of cell adsorption using human Mesenchymal stem cells reveal that hydroxyapatite coatings with strong texture and random orientation show different cell adsorption behavior, which is consistent with the notion that protein attach differently on different faces of hydroxyapatite crystals. Cells seeded on textured coatings exhibit better spreading and adhesion compared to those placed on randomly oriented coatings.

Electrostatic spray assisted vapour deposition and structural characterisation of cerium oxide films on biaxially textured Ni tapes

CeO2 thin films were successfully deposited onto biaxially textured Ni tapes at a temperature between 400 and 600 °C using electrostatic spray assisted vapour deposition (ESAVD). The surface morphology and microstructure of the deposited CeO2 films were characterized using high-resolution scanning electron microscopy. The preferred orientation of both Ni tape and CeO2 films was characterised using both X-ray diffraction and pole figure measurements. It has been found that highly textured CeO2 films were formed epitaxially on biaxially textured Ni substrates. The orientation relationships between CeO2 film and Ni substrate are 001CeO2//001Ni and 110CeO2//100Ni. FWHM of the 111 Φ scans from both film and substrate were also recorded and compared, which shows the good CeO2 film alignment has been achieved. The results show that ESAVD is a promising and cost-effective deposition technique to form thin epitaxial CeO2 buffer layers onto Ni tapes for subsequent deposition of high-temperature superconducting oxides.

Epitaxial growth of [formula omitted] Heusler alloy thin films on MgO (0 0 1) substrates by magnetron sputtering

We demonstrate that single-crystalline epitaxial films of the Heusler alloy Co 2 Cr 0.6 Fe 0.4 Al (CCFA) featuring excellent surface flatness can be grown on MgO (0 0 1) substrates by magnetron sputtering deposition at room temperature and subsequent annealing at high temperatures. X-ray pole figure measurements reveal that the films exhibit the B2-type structure and the [1 0 0] direction of the films is rotated by 45° from the [1 0 0] direction of the MgO substrate. Moreover, their Curie temperatures and saturation magnetizations are also improved by annealing. The surface roughness is about 0.2 nm rms according to atomic force microscopy.

Investigations of structure and morphology of the AlN nano-pillar crystal films prepared by halide chemical vapor deposition under atmospheric pressure

Abstract Aluminum nitride (AlN) prepared under atmospheric pressure using a halide chemical vapor deposition method has been examined by means of a variety of analytical techniques. Scanning electron microscopic observations showed that the crystals deposited onto a Si(100) substrate have hexagonal pillar structure. Based on the X-ray diffraction and X-ray pole-figure analyses, it was deduced that the each AlN pillar crystal grows with a different rotation angle around the 〈001〉 axis. Transmission electron diffraction showed that they are of single-like form. This was also confirmed by the selected area electron diffraction image as well. It was found that the diameter of pillar which constitutes an AlN film was significantly dependent upon the ratio of NH3/AlCl3 used as source materials and the growth temperature.

Characterization of Highly-Oriented Ferroelectric PbxBa1−x TiO3 Thin Films Grown by Metalorganic Chemical Vapor Deposition

PbxBa1−xTiO3 (0.2 ⩽ x ⩽ 1) thin films were deposited on single-crystal MgO as well as amorphous Si3N4/Si substrates using biaxially textured MgO buffer templates, grown by ion beam-assisted deposition (IBAD). The ferroelectric films were stoichiometric and highly oriented, with only (001) and (100) orientations evident in x-ray diffraction (XRD) scans. Films on biaxially textured templates had smaller grains (60 nm average) than those deposited on single-crystal MgO (300 nm average). Electron backscatter diffraction (EBSD) has been used to study the microtexture on both types of substrates and the results were consistent with x-ray pole figures and transmission electron microscopy (TEM) micrographs that indicated the presence of 90° domain boundaries, twins, in films deposited on single-crystal MgO substrates. In contrast, films on biaxially textured substrates consisted of small single-domain grains that were either c or a oriented. The surface-sensitive EBSD technique was used to measure the tetragonal tilt angle as well as in-plane and out-of-plane texture. High-temperature x-ray diffraction (HTXRD) of films with 90° domain walls indicated large changes, as much as 60%, in the c and a domain fractions with temperature, while such changes were not observed for PbxBa1−xTiO3 (PBT) films on biaxially textured MgO/Si3N4/Si substrates, which lacked 90° domain boundaries.

Crystal growth of CaMn 1−xMo xO 3 perovskites by the floating-zone technique ( [formula omitted

The crystal growth of perovskite manganites with composition CaMn 1− x Mo x O 3 ( 0 ⩽ x ⩽ 0.15 ) by the floating zone technique is reported. An air over-pressure is used to avoid the loss of manganese and molybdenum during the growth. The effect of the growth parameters (atmosphere, pressure, speed) on the quality of the crystals is discussed for several compositions. The crystals were characterized by X-ray (diffraction and pole figures) and electron probe microanalysis. Magnetization data are also presented.

Flux growth of BiFeO 3–PbTiO 3 single crystals

Single crystals of BiFeO 3–PbTiO 3 have been grown from a PbO:Bi 2O 3 flux by cooling at a rate of 2 °C/h from the melt. Faceted crystals of various morphologies were produced and the size of the crystals ranged from less than 0.5 to 5 mm. The crystals were reflective with smooth facets. Initial measurements were made using scanning electron microscope (SEM) with energy-dispersive X-ray analysis (EDX), quantifying the approximate composition of the crystals. Powder X-ray diffraction (XRD) of the crushed and sieved crystals established that the structure was rhombohedral perovskite for the (BiFeO 3) 0.75–(PbTiO 3) 0.25 composition and tetragonal perovskite for the (BiFeO 3) 0.50–(PbTiO 3) 0.50 composition. X-ray pole figures verified that the (BiFeO 3) 0.75–(PbTiO 3) 0.25 crystal had grown with a single orientation, the [1 0 0] direction. As grown, un-poled (BiFeO 3) 0.75–(PbTiO 3) 0.25 crystals exhibited a piezoelectric coefficient ( d 33) of 18 pC/N in the 〈1 0 0〉 direction.

Texture Analysis of Thin In2O3:Sn Films Prepared by Direct-current and Radio-frequency Magnetron-sputtering

Thin In2O3:Sn (ITO) films prepared by radio-frequency (rf) or direct-current (dc) magnetron-sputtering and in central or peripheral position relative to the target were characterized by x-ray diffractograms and pole figures. The diffractograms were normalized with the powder diffraction intensities of the target. In the normalized diffractograms, a random texture level and preferred orientations can be distinguished. The pole figures are represented by normalized χ-scans that are modeled as a sum of Gaussian curves. The centers of the Gaussian curves are consistent with the prominent orientations of the normalized diffractograms. The textures of the rf-sputtered films in the central and the peripheral position are similar, showing strong contributions from (211)-planes. The texture of dc-sputtered samples is dominated by (400) and (411) planes. In the peripheral sample, the distribution of (400)- and (411)-oriented grains is shifted towards the incidence angle of the particle flux and the frequency of the (222)-grains is suppressed below the random texture level. The results are discussed with reference to a model of incorporation of interstitial oxygen into the growing films.

Deposition of cerium oxide films on Si (1 0 0) and glass substrates using the ESAVD method

CeO 2 thin films were deposited onto both Si (1 0 0) and glass substrates at a temperature between 400 and 600 °C using electrostatic spray-assisted vapour deposition (ESAVD). A DC voltage, ranging from 5 to 20 kV, was applied between nozzle and substrate. The surface morphology and microstructure of deposited CeO 2 films were characterised using atomic force microscopy (AFM) and high-resolution scanning electron microscopy (HRSEM). The preferred orientation of the CeO 2 films produced on Si (1 0 0) was revealed using both X-ray diffraction and pole figure measurements. Highly textured CeO 2 films were formed epitaxially onto Si (1 0 0) substrates. The orientation relationships between CeO 2 film and Si substrate were 0 0 1 CeO 2 / / 0 0 1 Si and 1 1 1 CeO 2 / / 1 1 1 Si . However, no distinct alignment was observed in the CeO 2 films deposited on glass. The results show that ESAVD is a promising deposition technique to form thin epitaxial CeO 2 buffer layers onto Si (1 0 0), which is essential for the subsequent deposition of other functional oxide films, such as high-temperature superconducting oxides.

Epitaxial Growth of Fe/MgO/Fe Heterostructures on SrTiO3(001) Substrates by Magnetron Sputtering

We report on the preparation and structural properties of MgO/Fe bilayers (a MgO thin film on an Fe thin film), Fe/MgO bilayers (an Fe thin film on a MgO thin film), and Fe/MgO/Fe trilayers, all grown by magnetron sputtering on SrTiO3(001) substrates. We investigated the structural properties of these heterostructures with X-ray diffraction (XRD) (θ–2 θ scan, rocking curve and pole figure measurements), atomic force microscopy (AFM), and high-resolution transmission electron microscopy (HRTEM). Single-crystalline epitaxial growth was confirmed by the X-ray pole figure measurements for both the MgO/Fe and Fe/MgO bilayers, which were the basic layer components for the Fe/MgO/Fe trilayer. The cross-sectional HRTEM clearly indicated epitaxial growth of the Fe/MgO/Fe trilayer structures on the SrTiO3(001) substrates with excellent flat interfaces having roughness of less than a few angstroms.

Fabrication of YBCO coated conductor by TFA-MOD method in route of dissolving Y211 and Ba3Cu5O8 powders in TFA

We fabricated YBCO coated conductors using a new TFA-MOD method and evaluated the phase formation, texture evolution, and critical properties as a function of the firing temperature and oxygen heat treatment time, in order to explore its possible application in CCs fabrication. In the fabrication process, Y2Ba1Cu1Ox and Ba3Cu5O8 powders were used as precursors, instead of Y-, Ba- and Cu-based acetate or organics, and dissolved in trifluoroacetic acid followed by firing and oxygen heat treatment.We observed that for the films fired at 725°C, BaF2 and other second phases formed and Tc was measured to be 66.5K. In contrast, when the film was fired at 775°C, strong and sharp (00l) diffraction peaks of YBCO were observed, without the formation of the BaF2 phase. In addition, X-ray pole-figure analysis indicated that a strong biaxial texture was developed and the full-width at half-maximums of in-plane and out-of-plane textures were 4.38° and 4.26°, respectively. The critical temperature and current were also increased to 85.3K and 35.8A/cm-width, respectively, at 77K when the oxygen heat treatment time was increased to 20h. Microstructure observation indicated that a crack-free surface was obtained and that there was no a-axis grain growth.