X-ray Pole Figure Research Articles

Determination of the wurtzite content and orientation distribution of nanowire ensembles

AbstractWe present x-ray diffraction based methods to quantitatively determine the wurtzite content of nanowire ensembles and to investigate the effect of twinning. An increased lattice constant in growth direction is found for all investigated InAs and InP nanowire samples. This increase is independent of the wurtzite content. Using x-ray pole figures we find that twinning is present in GaAs/Si branched nanowires, which leads to 60° rotations of the lattice.

ＡＺ９１圧延材の高温における超塑性挙動

n 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 673K, 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 648K 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 control of sputtered HfN thin films using low oxygen partial pressures

The authors studied the development of crystallographic texture in hafnium nitride (HfN) films deposited by off-normal incidence reactive magnetron sputtering at room temperature. Films are prepared with and without added oxygen in N2∕Ar mixtures. Texture measurements were performed by x-ray pole figure analysis of the (111) and (200) diffraction peaks. The authors found that HfN deposited at 40° without added oxygen has a strong ⟨100⟩ fiber texture with no in-plane alignments showing the dominance of thermodynamic effects in the course of texture evolution. Oxygen is deliberately introduced into the sputtering gas ambient to study its effects on microstructure formation. As the oxygen partial pressure (O2 pp) is increased in the range of 1.33×10−5to1.33×10−4Pa, HfN out-of-plane orientation changed to ⟨111⟩ with a substantial in-plane alignment in ⟨100⟩ direction as well. In this case, texture analysis of each individual diffraction peak revealed the existence of two populations of grains indicating a competition between (111) and (200) planes. A transition towards hafnium oxynitride phases occurred at high O2 pp’s. The authors propose that oxygen presence during deposition reduces the adatom surface mobility, which enables kinetic effects to govern the texture formation and thus leads to a biaxial alignment in HfN films.

Fabrication and Characterization of a (100) Three-Axis-Oriented Single-Crystal (Ba0.7Sr0.3)TiO3Thin Film Prepared by the Chemical Solution Deposition Method

Epitaxially grown single-crystal perovskite (100) three-axis-oriented (Ba0.7Sr0.3)TiO3 thin films were prepared on a (100) platinum-coated (100) magnesium oxide (MgO) single-crystal substrate by the chemical solution deposition method using a solution derived from Ba(CH3COO)2, Sr(CH3COO)2, and Ti(O-i-C3H7)4. The growth of the film was found to depend on the annealing condition. A (Ba,Sr)TiO3 thin film annealed at 1073 K was found to be a single crystal by transmission electron microscope. The single-crystal film exhibited a (100) three-axis orientation that followed the (100) orientation of the Pt substrate, as observed from an X-ray pole figure measurement and selected area electron diffraction patterns.

Molecular Orientation and Degree of Crystallinity of Piezoelectric Poly(Vinylidene Fluoride) Films Exclusively in the β Phase

Oriented β -phase films were obtained by drawing exclusively β -phase films obtained from dimethylformamide solution crystallization at 60 °C with subsequent pressing. Wide angle X-ray diffraction and pole figure plots showed that drawing at 90°C and with R = 4 of originally β -phase films results in exclusively β -phase films with crystallinity degree of 49% and orientation factor of 0.885. For comparison, with the conventional drawing technique from α-phase material, films oriented at a ratio (R) of 5 still contain about 20% of phase α, a crystallinity degree of 40% and β -phase crystallographic c-axis orientation factor of 0.655.

Differences between magnetic and mineral fabrics in low-grade, cleaved siliciclastic pelites: A case study from the Anglo-Brabant Deformation Belt (Belgium)

Theoretically, within a given pelitic rock in which the main paramagnetic carriers are white mica and chlorite and in which, judging from the AMS parameters, AMS is controlled by the paramagnetic carriers, the results of X-ray pole figure goniometry should show a qualitative relationship with AMS. This idea is tested on single-phase deformed, low-grade pelites of the Lower Palaeozoic Brabant Massif (Belgium), representing the southeastern part of the Anglo–Brabant Deformation Belt. For the vast majority of the samples investigated, the different LF-AMS parameters suggest a paramagnetic control on LF-AMS. Different parameters of LF-AMS measured at 77 K (low- T LF-AMS) and a comparison of these with the LF-AMS parameters indicate that LF-AMS is controlled virtually entirely by paramagnetic carriers. High-field torque magnetometry (HF-AMS) indicates further that AMS is controlled entirely by paramagnetic carriers for the vast majority of the samples. Two apparent discrepancies are observed, however. These are 1) a frequent mismatch between the LF-AMS fabric on the one hand and the (paramagnetic) fabric indicated by low- T LF-AMS and HF-AMS on the other hand, and 2) a rather common mismatch between the preferred orientation of chlorite and white mica suggested by X-ray pole figure goniometry on the one hand and the LF-AMS fabric, low- T LF-AMS fabric and HF-AMS paramagnetic fabric on the other hand. These apparent discrepancies may partly be attributed to the composite nature of both the LF-AMS fabric and the paramagnetic susceptibility fabric. The presence of different populations of paramagnetic carriers, possibly in combination with minor traces of ferromagnetic (s.l.) carriers which are not picked up by the methods applied, may explain some of the mismatches observed and are compatible with the basin evolution history of the Brabant Massif. In addition, it is possible that the low temperatures (low- T LF-AMS) and high fields (HF-AMS) are capable of enhancing one of the paramagnetic phases, thus leading to discrepancies between methods that define the mineral and the magnetic fabrics. The results of this study show that, even when the LF-AMS data suggest that the LF-AMS of a given pelitic rock in which phyllosilicates form the main paramagnetic carriers, is controlled entirely by paramagnetic carriers, alternative methods, such as phyllosilicate X-ray pole figure goniometry, will not necessarily reflect the paramagnetic carrier orientation. Although a number of cases have successfully correlated LF-AMS with mineral fabric and occasionally even strain, this study serves as an example for how methods to define mineral and magnetic fabrics can be sensitive in detecting different paramagnetic phases.

Fiber textures of titanium nitride and hafnium nitride thin films deposited by off-normal incidence magnetron sputtering

We studied the development of crystallographic texture in titanium nitride (TiN) and hafnium nitride (HfN) films deposited by off-normal incidence reactive magnetron sputtering at room temperature. Texture measurements were performed by x-ray pole figure analysis of the (111) and (200) diffraction peaks. For a deposition angle of 40° from substrate normal, we obtained TiN biaxial textures for a range of deposition conditions using radio frequency (rf) sputtering. Typically, we find that the ⟨111⟩ orientation is close to the substrate normal and the ⟨100⟩ orientation is close to the direction of the deposition source, showing substantial in-plane alignment. We also introduced a 150 eV ion beam at 55° with respect to substrate normal during rf sputtering of TiN. Ion beam enhancement caused TiN to align its out-of-plane texture along ⟨100⟩ orientation. In this case, (200) planes are slightly tilted with respect to the substrate normal away from the ion beam source, and (111) planes are tilted 50° toward the ion beam source. For comparison, we found that HfN deposited at 40° without ion bombardment has a strong ⟨100⟩ orientation parallel to the substrate normal. These results are consistent with momentum transfer among adatoms and ions followed by an increase in surface diffusion of the adatoms on (200) surfaces. The type of fiber texture results from a competition among texture mechanisms related to surface mobilities of adatoms, geometrical, and directional effects.

The morphology and texture of Cu nanorod films grown by controlling the directional fluxin physical vapor deposition

We report the creation of unusual biaxial textures in Cu nanorod films,through the control of the incident vapor flux during oblique angle deposition.High-density twin boundaries were formed using a periodic azimuthal swingrotation of the substrate while the incident angle of the Cu flux was fixed at85° with respect to the surface normal. In contrast, depositions on stationary substratesresulted in nanorod films with a much lower density of twinned crystals. From transmissionelectron microscopy and x-ray pole figure analysis, the nanorod axis was shown to coincideapproximately with the crystallographic directions. We also observed the branching of these nanostructures into‘nanotrees’. This branching was attributed to the creation of edge dislocations during thedeposition and was particularly prevalent for the case of swing rotation. The mechanismsfor the development of texture, twinning, and branching in these nanostructures arediscussed.

Ti 2AlC coatings deposited by High Velocity Oxy-Fuel spraying

High Velocity Oxy-Fuel has been utilized to spray coatings from Ti 2AlC ( MAXTHAL 211 ®) powders. X-ray diffraction showed that the coatings consist predominantly of Ti 2AlC with inclusions of the phases Ti 3AlC 2, TiC, and Al–Ti alloys. The fraction of Ti 2AlC in coatings sprayed with a powder size of 38 μm was found to increase with decreasing power of the spraying flame as controlled by the total gas flow of H 2 and O 2. A more coarse powder (56 μm) is less sensitive to the total gas flow and retains higher volume fraction of MAX-phase in the coatings, however, at the expense of increasing porosity. X-ray pole figure measurements showed a preferred crystal orientation in the coatings with the Ti 2AlC (000 l) planes aligned to the substrate surface. Bending tests show a good adhesion to stainless steel substrates and indentation yields a hardness of 3–5 GPa for the coatings sprayed with a powder size of 38 μm.

Crystal Orientation of Epitaxial α-Ta(110) Thin Films Grown on Si(100) and Si(111) Substrates by Sputtering

We have prepared Ta thin films on Si(100) and Si(111) substrates by increasing the substrate temperature from room temperature (RT) to 500 °C, using an ultrahigh-vacuum dc magnetron sputtering system. The obtained film crystallinities were evaluated by X-ray diffraction and X-ray pole figure analyses. It was found that the crystal phase of the prepared Ta films transforms gradually from the β-Ta phase to the α-Ta phase with increasing substrate temperature, and the epitaxial growth of the α-Ta(110) plane was realized at substrate temperatures of 400 °C on Si(100) and 200 °C on Si(111). In addition, it was also clarified that the α-Ta(110) films are grown epitaxially in a twin state on Si(100), while they are grown epitaxially in a triplet state on Si(111).

Orientation relationship of polycrystalline Pd-doped SnO 2 thin film deposits on sapphire substrates

Pd-doped SnO 2 thin films of rutile structure were deposited using radio-frequency magnetron sputtering method on sapphire substrates with three different orientations: r-cut (0112), a-cut (1120), and m-cut (1010). The deposited films were characterized using transmission electron microscopy and X-ray pole figures. All the deposited films were polycrystalline but highly oriented with the interface, and also had in-plane or near-epitaxial relationships were observed for the SnO 2 films grown on all three cases of sapphire substrates. In particular, (101), (101), and (001) oriented films were respectively grown on r-, a-, and m-cut sapphire substrates. The in-plane orientation relationships were determined to be [010]SnO 2 || [100]Al 2O 3 and [101]SnO 2 || [121]Al 2O 3 (r-cut), [101]SnO 2 || [110]Al 2O 3 and [010]SnO 2 || [001]Al 2O 3 (a-cut), and [100]SnO 2 || [010]Al 2O 3 and [010]SnO 2 || [001]Al 2O 3 (m-cut). A highly textured structure was observed for the films grown on m-cut substrate.

Structure and Properties of Self-Organized TiO2 Nanotubes from Stirred Baths

Self-organized porous nanotubular TiO2 was anodically formed on titanium in 1M Na2SO4 electrolyte containing 0.5 wt pct NaF. The oxidation was carried out for 0.5, 1, 2, and 4 hours at 20 V with the baths stirred using (1) magnetic pellet and (2) ultrasonic vibration. During the initial stages of oxidation, a barrier type of oxide film is formed, which gives rise to the formation of pores beneath it. With increasing time of oxidation, the pores self-organize to tubular structure. Of the two types of agitation studied, ultrasonics help in earlier complete removal of the barrier layer. The nanotubes have single-pore diameter of 50 to 90 nm under the magnetic pellet conditions and 55 to 110 nm under the ultrasonic agitation condition. The porosity was of the order of 24 to 30 pct for both types. The charges that have flown onto the coatings are greater under the ultrasonated condition. The as-oxidized coatings were amorphous for both types. The coatings obtained by using magnetic pellet had lower tensile adhesion strengths than those obtained using ultrasonic agitation. Heat treatment for 2 hours at 500 °C maintained the tubular morphology and converted the amorphous coatings to anatase TiO2. These anatase containing coatings were analyzed for texture by X-ray pole figures, and it was found that (101) and (200) poles were randomly oriented.

Structural characterization of multi-coated YBCO films processed by metal-organic deposition method

YBCO films were fabricated using the TFA–MOD process. The effects of film thickness on phase formation, degree of texture, microstructures, and critical properties were evaluated by X-ray diffraction, pole-figure, and transmission electron microscopy. The films were prepared with various thicknesses by producing multi-coated films by repeating the dip-coating and calcining processes. The microstructure and resultant critical current ( I c) and critical current density ( J c) varied remarkably with film thickness: the I c increased from 39 to 169 A/cm-width, while J c ranged from 0.85 to 0.92 MA/cm 2 with increasing number of coatings from one to three or four. Both values decreased when further coatings were applied as a result of microstructural degradation. It is believed that this decrease in I c for the multi-coated film is partly due to the presence of a second phase, pores, and poor texture formability. The optimum thickness for maximizing both the I c and J c values is believed to be in the range of 1.1–1.7 μm.

Biaxially oriented CaF 2 films on amorphous substrates

Biaxially oriented CaF 2 films have been created by first using an oblique incidence vapor flux to deposit CaF 2 onto an amorphous surface to form vertically aligned nanorods which served as seeds to grow a more continuous CaF 2 capping layer under a subsequent normal incidence flux deposition. The entire film possesses a unique {1 1 1}〈1 2 1〉 biaxial texture as shown by X-ray pole figure analysis and transmission electron microscopy (TEM). This unique texture formation is a result of shadowing and surface diffusion effects. This biaxially oriented film on an amorphous substrate may be useful as a buffer layer to grow active semiconductor devices.

Texture in superplastically deformed alumina–zirconia composites

3Y-TZP/Al 2O 3 composites were prepared by hot-pressed sintering at 1450 °C for 1 h under 30 MPa in vacuum, and then the fine-grained composite sintered bodies were deformed by superplastic compression at 1500 °C. Quantitative texture analysis to the hot-pressed and deformed composites was accomplished via XRD and X-ray pole figure measurements. Highly oriented and textured microstructure was generated by superplastic deformation. The maximum degree of texture was up to 7.3 times random. The microstructure observation based on SEM and TEM was adopted to explain the development and mechanism of texture formation. The results indicated that Al 2O 3 matrix with fine platelike grains was formed in deformed materials, while the shape of ZrO 2 grains did not change obviously. The predominant mechanism for deformation and texture development was grain-boundary sliding and grain rotation, accompanying with anisotropic grain growth. Meanwhile, the intragranular dislocation motion played an important role in the formation of texture.

Epitaxial growth of HfB 2(0 0 0 1) on Si(0 0 1) by etching through a SiO 2 layer

Using the single-source chemical vapor deposition (CVD) precursor Hf(BH 4) 4, HfB 2 films can be grown epitaxially on Si substrates at 1000 °C by etching through a pre-existing SiO 2 layer. Despite the different symmetries in the plane of the interface, the film is oriented with HfB 2 (0 0 0 1)∥Si(0 0 1) and the X-ray rocking curve is exceptionally sharp, with full-width at half-maximum (FWHM)=0.076°. Top-view scanning electron microscope (SEM) micrographs show that the film consists of micrometer size domains on the substrate. X-ray pole figures and electron backscattering diffraction studies indicate the existence of four types of domains with in-plane orientations rotated 45° from each other, HfB 2[2 1 1 0]∥Si[1 0 0] and HfB 2[2 1 1 0]∥Si[1 1 0].

Uniaxially Oriented, Highly Ordered, Large Area Columnar Superstructures of Discotic Supramolecules using Magnetic Field and Surface Interactions

This work was supported by the Basic Atomic Energy Research Institute (BAERI) program of the Ministry of Science & Technology (MOST) of Korea. CHESS is a national user facility supported by the National Science Foundation and the National Institutes of Health/ National Institute of General Medical Sciences under Award DMR-0225180 and the X-ray laboratory supported by DOE Grant DEFG02-97ER62443. We would like to thank Mr. Sang-Geul Lee at the KBSI for his help during X-ray pole figure measurement.

The role of lattice mismatch and kinetics in texture development: Co1−xNixSi2 thin films on Si(100)

Mixed Co1−xNixSi2 films (0≤x≤1) were grown by solid phase reaction of homogeneous Co1−xNix metal films, codeposited on Si(100). The texture of these films was contemplated using complementary experimental techniques: Rutherford backscattering and channeling spectrometry, x-ray pole figure measurements, and orientation imaging with electron backscattering diffraction. Based on the increasing Co1−xNixSi2 lattice parameter with increasing Ni concentration, a gradual, continuous improvement of the epitaxial quality of the film would be expected. The observed trend is significantly different. The epitaxial quality of the disilicide film indeed improves with increasing Ni concentration, but only up to 15% Ni. Moreover, the increasing epitaxial quality is due to a large volume fraction of (110)-oriented grains, instead of the anticipated (100) orientation. The most abundant texture component is not necessarily the one with the best in-plane match with the substrate, i.e., epitaxy, nor the one which assures the continuity of crystallographic planes across the plane of the interface, i.e., axiotaxy. Clearly, geometrical arguments alone cannot account for the observed large size and high volume fraction of (110)-oriented grains. On the other hand, we demonstrate that growth kinetics plays an important role in texture development and epitaxial growth during the solid phase reaction. Above 15% Ni, the epitaxial quality rapidly decreases and a polycrystalline film is formed for 40% Ni. This decrease is explained by a gradual shift of the disilicide nucleation site from the interface with the substrate to the surface of the thin film. For high Ni concentrations, i.e., ≥50% Ni, the (100) orientation dominates the thin-film texture, due to the growth of a NiSi2-rich film at the substrate interface. The changing nucleation site, due to this phase separation, and the differing growth kinetics can significantly alter the texture of ternary films. These two factors should be taken into consideration when implementing ternary alloys in devices, since their physical properties, stability, roughness, resistance, etc., depend critically on the texture of the films.

Epitaxial Growth of (0001)Ru Thin Films on (111)ZrN/(111)Si by Low-Temperature Process and Their Surface Morphologies

We have investigated the epitaxial growth of (0001)Ru thin films on (111)ZrN/(111)Si epitaxial systems at room temperature using an ultrahigh-vacuum dc magnetron sputtering system. The film quality obtained and the epitaxial relationship were evaluated by X-ray diffraction, X-ray pole figure, grazing-incidence-angle X-ray reflectivity, and atomic force microscopy analyses. It was found that (0001)Ru films with a thickness of 100 nm were grown epitaxially on a (111)ZrN(40 nm)/(111)Si system even at room temperature with the directional relationship of Ru(0001)[1120]∥ZrN(111)[110]∥Si(111)[110]. In addition, it was also clarified that an epitaxial (0001)Ru film with a thickness of 3 nm on a (111)ZrN (6 nm)/(111)Si system can be regarded as a dense film with the same density as the bulk, and exhibits a fairly flat surface morphology with an average surface roughness of approximately 0.2–0.3 nm.

Development of texture and morphology in Cu-Ag thin nanocomposite films on Si

Cu-Ag films were deposited in vacuum of 10−5−10−6 mbar onto freshly cleaned Si wafers. The composition of the films corresponded to Cu, Cu9Ag1, Cu4Ag6 and Ag. The films were investigated by X-ray diffraction and pole figures of <111> and <100> directions were recorded. TEM and XTEM were used to determine the morphological properties of the films. We found that Ag modifies the interaction of Cu with the Si substrate. Low amounts of Ag are enhancing the formation of the biaxial <100> texture of Cu. Larger amounts of Ag result in the formation of <111> wire texture of both Ag and Cu components.