In-plane XRD Research Articles

Synthesis of Monodisperse PbSe Nanorods: A Case for Oriented Attachment

Monodisperse, high-quality, single-crystal PbSe nanorods were synthesized in a catalyst-free, one-pot reaction using a new phosphine selenide precursor. PbSe nanorods were assembled to provide liquid-crystalline alignment or vertical alignment under controlled evaporation conditions. The growth of nanorods was monitored by TEM and absorption spectroscopy, indicating that oriented attachment could be involved to provide anisotropic PbSe nanostructures. In-plane XRD showed an enhanced (200) peak for PbSe nanorods, indicating the preferred alignment of nanorods on the substrates and their growth along the <100> direction. Absorption and emission spectra, along with lifetime measurements, show the differences between nanoscale PbSe spheres and rods.

Growth and characterization of GaSb/AlSb multiple quantum well structures on Si(111) and Si(001) substrates

For the purpose of investigating their structural and optical properties, GaSb thin films and GaSb/AlSb multiple quantum well (MQW) structures were grown on Si(111) substrates. A GaSb/AlSb MQW structure was also grown on Si(001) substrate as a control sample. Surface morphologies and a XRD measurements of GaSb films grown on Si(111) substrates showed that the GaSb film with a 5 nm thick AlSb initiation layer has good crystal quality. Observation of the RHEED patterns of both MQWs suggests that both GaSb films are under tensile strain at growth temperature. In-plane XRD measurement of MQW on Si(111) showed that the (111) face of the GaSb film is aligned to the Si(111) surface upon rotation by 30°. Photoluminescence (PL) spectra consisting of two peaks at 1250∼1400 nm were observed for both MQWs.

Self-Movement Inducing On-Demand Pattern of Mesoporous Silica Thin Film with Oriented Mesochannels

An on-demand pattern of mesoporous thin film with oriented mesochannels was attractive for the application of mesoporous thin film in wide fields. In this work, we reported the preparation of such a featured mesoporous silica thin film based on self-movement of solution on a laser pattern-irradiated polyimide film. SEM and EDS observation confirmed that the deposition of silica sol precursor showed strict selectivity on such an irradiated polyimide film surface with aid of photomask: aggregation occurred only on the irradiated region and not on the nonirradiation region. TEM and In-plane XRD results proved that mesochannels in the patterned silica thin film oriented along laser induced surface periodic microgrooves (LIPS). The selective pattern of silica sol solution on the laser pattern-irradiated polyimide surface was attributed to the difference in surface energy between irradiated and nonirradiated regions according to the calculating result based on the contacting angle measurement, which leads to se...

Lamellar self-assembly of a porphyrin derivative possessing poly(ethylene oxide) methyl ether and the formation of a silica–porphyrin hybrid with tetraethoxysilane

A porphyrin derivative, possessing poly(ethylene oxide) methyl ether on the para positions of phenyl groups in the tetraphenylporphyrin, is self-assembled to form a thin film with a lamellar structure. A split of the absorption band in the visible light region of the film strongly indicates the stacking of the porphyrin rings in the film. A molecular periodicity perpendicular to the substrate, proven by in-plane XRD, suggests the perpendicular orientation of the porphyrin rings. A silica–porphyrin hybrid film with a mesostructure was prepared from the mixture of the derivative and tetraethoxysilane. The mesoscale periodicity of the hybrid was confirmed by low-angle XRD and TEM data. The presence of the grafted groups suppressed the segregation of tetraphenylporphyrin rings in the formation of the hybrids, which is in clear contrast to the separated precipitation of tetraphenylporphyrin from a mixture of underivatized tetraphenylporphyrin and hydrolyzed tetraethoxysilane. These results indicate that porphyrin derivatives can be utilized as the organic components in silica–organic hybrids if they are appropriately derivatized.

Change in the Orientation and Packing upon Adsorption of Pyranine Molecules onto Cationic Langmuir Monolayers and Langmuir–Blodgett Films

Abstract Differrent adsorption behaviors and the orientation of pyranine molecules were investigated for the cationic Langmuir monolayers by using Brewster angle microscopy (BAM), two-dimensional (2D) phase behavior with elasticitic property of the monolayers and in situ visible spectroscopy. The structural change in the cationic Langmuir–Blodgett (LB) films before and after adsorbing pyranine molecules was found by using small angle and in-plane XRD. The excited-state proton-transfer (ESPT) between octadecylamine (ODA) and pyranine adsorbed in the films was investigated using time-resolved fluorescence spectroscopy together with consideration of the film structures.

X-ray Analysis of Strain Relaxed Domain Structure in (100)/(001)-oriented epitaxial PbTiO3 thick films grown on (100)SrTiO3 substrates

AbstractCrystal structure of epitaxially grown (100)/(100)-oriented PbTiO3 films on (100)SrTiO3 substrates with 3.8 μm in thickness was investigated by the XRD reciprocal space mapping techniques. The observed poles of PbTiO3004, 400, 204, 402 and 420 scans can be successfully explained using the model consisting with the one type of (001) domain and three types of (100) domains in good agreement with the estimation from the scanning probe microscopy in conjunction with the in-plane and out-of plain XRD analysis.

Magnetically induced orientation of mesochannels in 2D-hexagonal mesoporous silica films

Mesoporous silica films with uniaxially oriented mesochannels were prepared by dip coating under a steady-homogeneous magnetic field parallel to a substrate. The effect of a strong magnetic field (12 Tesla) on the preparation of mesoporous silica films was systematically investigated by using two kinds of templates. When mesoporous silica films with a 2D-hexagonal structure were prepared by using an ionic CTAB (hexadecyltrimethylammonium bromide)-based precursor solution, the in-plane XRD results of the films proved that the mesochannels were slightly oriented parallel to the magnetic field. When mesoporous silica films were prepared by using a non-ionic P123 (polyethylene oxide–polypropylene oxide–polyethylene oxide triblock copolymer)-based precursor solution, the directional distribution of the mesochannels became narrow (FWHM was about 20°). The use of large molecules such as triblock copolymers leads to successful magnetically induced orientation. The spatial orientations of the magnetically aligned mesochannels are elucidated by θ–2θ XRD, in-plane XRD, cross-sectional transmission electron microscopy (TEM), and high resolution scanning electron microscopy (HR-SEM).

Epitactic growth of a decagonal phase in an Al–Ni–Co alloy film deposited on a (0001) sapphire substrate

Thin films of Al–Ni–Co alloy with an average thickness of 15 nm were produced by means of conventional vacuum deposition technique on (0001) sapphire substrates heated at various test temperatures. The microstructures and textures of the films obtained were thoroughly investigated by atomic force microscopy, X-ray diffraction and transmission electron diffraction and imaging techniques. The diffraction measurements have evidenced that the vacuum deposition of Al72Ni15Co13 alloy on the substrates heated above 400°C allows a homogeneous poly-quasicrystalline film, consisting of the Ni-rich basic decagonal phase to grow. It has been further indicated by in-plane XRD analysis that the film deposited at 550°C contains a considerable amount of the decagonal grains epitaxially grown on the sapphire substrate. Possible epitaxial relations occurring between the deposit and the substrate will be detailed on the basis of results obtained from electron diffraction measurements.

Photocurrent Generation from Semiconducting Manganese Oxide Nanosheets in Response to Visible Light

Unilamellar nanosheet crystallites of manganese oxide generated the anodic photocurrent under visible light irradiation (lambda < 500 nm), while the nanosheets themselves were stable as revealed by in-plane XRD and UV-visible absorption spectra. The band gap energy was estimated to be 2.23 eV on the basis of the photocurrent action spectrum. The molecular thickness of approximately 0.5 nm may facilitate the charge separation of excited electrons and holes, which is generally very difficult for strongly localized d-d transitions. The monolayer film of MnO2 nanosheets exhibited the incident photon-to-electron conversion efficiency of 0.16% in response to the monochromatic light irradiation (lambda = 400 nm), which is comparable to those for sensitization of monolayer dyes adsorbed on a flat single-crystal surface. The efficiency declined with increasing the layer number of MnO2 nanosheets, although the optical absorption was enhanced. The recombination of the excited electron-hole pairs may become dominant when the carriers need to migrate a longer distance than 1 layer through multilayered nanosheets.

수직자기기록매체용 Fe-Co-B/M 하지연자성층의 미세결정구조 및 자기특성

It is necessary to develop soft magnetic layer with high saturation magnetization 4 <TEX>$\pi{M}_s$</TEX> and in-plane magnetic anisotropy field Hk for soft magnetic underlayer of perpendicular magnetic recording media with high signal to noise ratio. Fe-Co-B layer with high 4 <TEX>$\pi$</TEX>Ms of about 23 kG deposited on Ni-Fe and Ni-Fe/Si seedlayer exhibited very high in-plane magnetic anisotropy filed Hk of about 280 and 380 Oe, respectively, In-plane XRD studies clarified that the lattice spacing of planes along the easy axis direction was longer than that along the hard axis direction in the Fe-Co-B layers with high Hk. These results indicate that high Hk of Fe-Co-B/Ni-Fe and Fe-Co-B/［Ni-Fe/si］ layers were resulted from magnetoelastic anisotropy owing to a residual stress. Moreover, the high Hk in the Fe-Co-B/Ni-Fe layer was maintained until 30<TEX>$0^{\circ}C$</TEX> annealing temperature.

Physical and Electrical Properties of Al2O3, HfO2, and their Alloy Films Prepared by Atomic Layer Deposition for 65nm CMOS Gate Dielectric

ABSTRACTWe have investigated physical and electrical properties of Al2O3, HfO2, and their alloy films deposited on 300mm Si wafers by Atomic Layer Deposition (ALD). It is found that Al2O3 films are not crystallized even after the heat treatment of 1050°C, while HfO2 films are already crystallized even after a-Si deposition (530°C). The crystallization temperature can be higher by adding Al2O3 to HfO2. It is confirmed by in-plane XRD and plane views of TEM that HfAlOx films with lower Hf content (Hf/(Hf+Al) &lt;30%) are amorphous without phase separation after annealing at 1050°C and 5sec. The dependences of equivalent oxide thicknesses (EOT) on the physical thicknesses of Al2O3, HfAlOx (Hf/(Hf+Al)∼22%), and HfO2 films in poly-silicon gate capacitors indicate that those dielectric constants k are ∼9, 14, and 23, respectively. The gate dielectric with EOT of 1.5nm and the leakage current density Jg of 3mA/cm2 can be fabricated with 2nm-thick HfAlOx (22%) film.

First observation of in-plane X-ray diffraction arising from a single layered inorganic compound film by a grazing incidence X-ray diffraction system with a conventional laboratory X-ray source

Grazing incidence angle in-plane X-ray diffraction (in-plane XRD) was applied to characterization of an organic–inorganic hybrid Langmuir–Blodgett (LB) film in a laboratory scale. The hybrid LB film consisted of octadecyl ammonium cation and sodium montmorillonite layers at Si(1 0 0) wafer. The in-plane XRD measurements of the hybrid LB film gave one diffraction peak at 20.0° (0.44 nm), which we assigned to the (1 1 0) and (0 2 0) reflections of montmorillonite. This was the first example of the in-plane diffraction from a single layered montmorillonite, presenting a clear evidence for the parallel orientation of the (0 0 1) plane with respect to a film surface.