篭島 靖

We have succeeded in developing two different X-ray microdiffraction methods to define optical devices with highly brilliant synchrotron radiation. In the first, we adopted perfect-crystal X-ray optics (successive asymmetric diffraction) and in the second, we used a phase zone plate to produce the X-ray microbeam. We used them to accurately measure the mask width dependence of strain change and lattice strain distribution in selective area growth layers.

The changes of surface morphology at nanometer scale during metal-organic vapour-phase epitaxial growth of indium phosphide have been investigated by using x-ray specular reflection at grazing incidence. At the low growth temperature of 400 degreesC, large decreases of x-ray beam intensity were observed, suggesting the formation of nanometer-sized nuclei. At a higher growth temperature of 500 degreesC, oscillations estimated to by layer-by-layer growth were observed, and roughness changes obtained from these oscillations were <0.01 nm, suggesting small-island formation on the terrace or step-edge fluctuation during the growth. Additionally, reflectivity increases at a growth temperature of 550degreesC were observed. Considering the reflectivity dependence on t-butylphosphine flow at 400 degreesC, the change of reflectivity at 550 degreesC is explained by the existence of phosphorus layers before the growth. Copyright (C) 2003 John Wiley Sons, Ltd.

We have developed an X-ray microbeam with a small angular divergence by adopting X-ray optics with successive use of asymmetric Bragg reflection from silicon crystals for the both polarizations of the synchrotron X-rays. The microbeam actually obtained is several microns in size and possesses an angular divergence of less than 2 arcsec which enables us to measure the strain of 10(-5)-10(-6). By scanning the sample against the microbeam, distribution of the minute local strain in various regions of semiconductor crystals for electronic devices, e.g., the strain around the SiO2/Si film edge in silicon devices, the strain in an InGaAsP/InP stripe laser were measured. (C) 2002 Elsevier Science B.V. All rights reserved.

Crystallinity of bonded silicon-on-insulator (SOI) wafers has been investigated by means of diffractometry using a parallel X-ray microbeam. Peak shifts and extended tails were observed in the rocking curves of the Sol layer. Further, reciprocal lattice maps revealed that the SOI lattice planes were tilt dispersively within about 100 murad. The typical sizes of the grains are ranging from a few pin to a several tens pm. The inferiority of the thin Sol crystal may arise from the extended force of buried oxide layer. (C) 2002 Elsevier Science B.V. All rights reserved.

Lattice strain distribution in a silicon substrate covered by an aluminum conductor film has been investigated by a highly parallel X-ray microbeam combined with synchrotron radiation. To evaluate a very local and Minute strain in the silicon substrate, intensity maps drawn from a series of rocking curves and reciprocal space intensity maps using an analyzer crystal were obtained using the X-ray microbeam. The results revealed that the deposition Of the aluminum layer gave rise to nonuniform strain distribution in the silicon Substrate through the silicon oxide layer and that the local strain in the silicon substrate beneath the aluminum film,vas mainly related to the lattice tilt variation. An intensity map of the rocking curves also revealed the large tilt of the lattice plane in the vicinity of the edge of the aluminum pad.

Synchrotron radiation total reflection X-ray fluorescence spectroscopy (SR-TXRF) was utilized to analyze various trace elements in small amounts of drugs of abuse. Sample amounts of 1 muL solutions containing 10 mug of drugs (methamphetamine. amphetamine, 3,4-methylene-dioxymethamphetamine, cocaine, and heroin) were spotted on silicon wafers for direct analysis. In addition, a leaflet of marijuana was set directly on a silicon wafer, and opium in the form of a soft lump was smeared on another silicon wafer for analysis In these experiments, about 10 pg of contaminant elements could be detected. For example, in a seized methamphetamine sample, iodine was found. which Could be indicative of synthetic route In seized 3,4-methylenedioxymethamphetamine samples, variable amounts of phosphorus, calcium, sulfur, and potassium were found, which could not be detected in a control 3,4-methylenedioxymethamphetamine sample. For marijuana and opium, two spectral patterns were obtained that were far different from each other and could be easily discriminated. Using SR-TXRF, pg amounts of each trace element in 10 mug of various drugs can be easily detected, which is not the case either for a standard TXRF experimental system or for other elemental analysis techniques.

We developed a micro-area, X-ray diffraction system using a sub-mum X-ray beam of 10 keV energy that was produced by a phase zone plate made of tantalum. Using this system, we were able to measure the lattice strain distribution in InGaAsP metalorganic vapor phase epitaxial layers selectively grown on InP stripe regions a few Am in width between a pair of SiO2 mask stripes, with strain sensitivity of about 1 x 10(-4). We found that the strain distribution in a 3-mum-wide stripe layer is almost completely uniform, while that in a 4-mum-wide layer is not.

An imaging transmission hard X-ray microscope has been constructed at beamline BL24XU of SPring-8. It makes use of a phase zone plate made of tantalum with a diameter of 1 mm and an outermost zone width of 50 nm, aiming at a wide field of view and a high spatial resolution. The performance test was carried out at a photon energy of 10 keV. A field of view as wide as similar to200 mm in diameter was achieved. The spatial resolution was measured to be 220 nm by analyzing a knife-edge image. Further, a line-and-space pattern as fine as 100 nm could be imaged. By placing a phase plate made of gold in the back focal plane of the zone plate, phase-contrast microscopy using Zernike's method was also carried out. The feasibility of phase-contrast microscopy for observing transparent samples was successfully demonstrated by imaging small polystyrene particles.

A micro-beam of hard X-ray (10 keV) as small as 5 mum in diameter has been generated using a single refractive lens (SRL) and been applied for direct writing, which may find possible applications in three-dimensional (3D) micro-fabrication. The refractive lenses are parabolic-shaped concave lenses with a radius of 4 pm and an aperture of 179 pm and have been produced using our high aspect-ratio techniques with synchrotron radiation (SR). (C) 2002 Elsevier Science B.V. All rights reserved.

sWe have developed an X-ray microbeam with a narrow energy bandwidth and a small angular divergence in both horizontal and vertical directions normal to the X-rays. Utilizing synchrotron radiation from the so-called third-generation ring like SPring-8 (Super Photon ring, 8 GeV), the X-ray microbeam possesses sufficient photons even after beam size compression. Using the X-ray microbeam, we have demonstrated to measure very local and minute lattice strain in silicon materials after some wafer preparation processes or device fabrication processes. Local strain in an Si crystal around the SiO2/Si film edge and also strain at silicon-on-insulator (Sol) interface have been measured as ;sample materials. (C) 2002 Elsevier Science B.V. All rights reserved.

The results of real-time X-ray reflectivity measurements of MOVPE grown indium phosphide surface are presented. At the low growth temperature of 450degreesC, large decreases of reflectivity were observed. Suggesting the formation of indium islands. At higher growth temperature of 550degreesC, only small changes were observed at high growth rate, indicating the step-flow growth mode. Oscillations longer than mono-layer growth were also observed at 500degreesC and 550degreesC, and roughness changes obtained from these oscillations were less than 0.01-nm suggesting small islands formation on the terrace or step-edge fluctuation during the growth. (C) 2002 Elsevier Science B.V. All rights reserved.

Using our recently developed technique of near-grazing angle x-ray surface reflection, we have studied the real-time atomic surface kinetics during metal organic vapor phase epitaxy of InP by monitoring the monolayer scale roughness during the growth. The evolution of the surface roughness for various group III and group V precursor flows has been reported. The step-flow mode of growth was observed at the growth temperatures of 550 degreesC and 525 degreesC and their characteristics have been discussed in details.

The spatial resolution of an imaging transmission hard X-ray microscope has been greatly enhanced by the use of all X-ray phase zone plate with a numerical aperture five times larger than the previous one [Y. Kagoshima, T. Ibuki, K. Takai, Y. Yokoyama, N. Miyamoto, Y. Tsusaka and J. Matsui: Jpn. J. Appl. Phys. 39 (2000) L433]. An experiment was carried out at the photon energy of 10 keV to evaluate the performance of the microscope. It was confirmed that the spatial resolution was 230 nm and that a Line-and-space pattern as fine as 100 nm could be imaged.

Hard X-ray phase-contrast microscopy has been performed with phase plates of tantalum using an X-ray beam from an undulator in SPring-8. The photon energy was set at 10 keV near the $L_{3}$ absorption edge of tantalum (9.9 keV) in order to increase the phase contrast. To demonstrate its capability, a transparent specimen was imaged clearly in the reverse contrast with phase plates to shift the phase by one-quarter and three-quarters of a period, while conventional absorption imaging showed little contrast. Further, an image contrast as high as approximately 40% can be obtained for the cell walls of another specimen.

High-resolution X-ray diffraction has been carried out by using a vertically and horizontally condensed X-ray microbeam at the Hyogo beamline (BL24XU) of SPring-8. The microbeam is 7 x 5 mum(2) in size and it possesses a small angular divergence and a narrow energy bandwidth. The sample is a Si substrate on which thermal oxide films are fabricated with fine patterns. At the region of the line-and-space pattern, many periodic peaks lying along the transverse direction are observed in a reciprocal space map. Those patterns are attributed to some local strain distribution due to the patterned oxide film on the Si wafer. (C) 2001 Elsevier Science B.V. All rights reserved.

Using highly parallel X-ray microbeam of 9 mum x 9 mum size and 1.8 arcsec angler divergence obtained by means of successive asymmetric reflections, measurements of the rocking curves of small electric devices was performed. The strain in a local region of LEDs under current operation was investigated. While changing the current. the deviation of the lattice constant around the surface was clearly observed. (C) 2001 Elsevier Science B.V. All rights reserved.

The Hyogo beamline has been constructed as the first contract beamline at SPring-8. It has three experimental hutches and their corresponding three monochromators. Two upstream transparent monochromators enable us to perform three experiments for different purposes simultaneously. Employing a figure-8 undulator, horizontally or vertically polarized X-rays can be obtained in a wide energy range. Rocking curves of the monochromators were almost identical to theoretical ones. (C) 2001 Elsevier Science B.V. All rights reserved.

A scanning hard X-ray microscope using a phase zone plate made of tantalum as its X-ray focusing device is in operation at the Hyogo-BL (BL24XU) of SPring-8. The X-ray microbeam has a size of 0.8 mum x 0.7 mum at the photon energy of 10 keV, which can make visible structures as fine as 250-nm line-and-space pattern. The photon flux density at the sample position is similar to 2 x 10(9) phs/s/mum(2) and the gain of the phase zone plate is similar to 3000. The minimum detection limits irradiated by the microbeam are evaluated to be around 10 ppm for some trace elements contained in standard reference materials of glass matrices. X-ray images obtained so far demonstrate a high feasibility of the microscope. (C) 2001 Elsevier Science B.V. All rights reserved.

Utilizing so called third-generation synchrotron radiation ring like SPring-8 (Super Photon ring, 8 GeV), we have developed the x-ray microbeam with a narrow energy bandwidth and a small angular divergence in both horizontal and vertical directions normal to the incoming x-rays. We have demonstrated to measure very local and minute lattice strain in silicon materials after some wafer preparation process or device fabrication process like a locally patterned SiO2/Si film or a silicon-on-insulator (SOI) sample.

High resolution X-ray fluorescence measurements were carried out using a flat analyzer crystal and an X-ray CCD (charge-coupled device). A comparison of the detector was made between the CCD and the position sensitive proportional counter (PSPC), and the advantage of the CCD in better spatial resolution and two-dimensional spatial resolution was demonstrated. Full width at half maximum (FWHM) of measured Cu Kα1,2 X-ray fluorescence spectra shows clear dependence of beam size on the sample, and the FWHM of 2.4 eV can be expected with the use of an X-ray microbeam. Copyright ©2001 by Marcel Dekker, Inc.

We show that a 10 keV X-ray has been focused into 3.4-8.4 mum at a focal length F = 0.4-1.5 m with a single refractive lens and such X-ray microbeams: can be generated in array. For the beam from a synchrotron radiation source, which typically had a diameter phi = 100 mum, transmissions of our lenses were measured to be T = 54-85%. X-ray imaging of a copper mesh was carried out with a magnification of about 5 in one dimension and the imaging resolution was evaluated to be 0.9 mum. Our lenses have performed well under a flux of 1.1 x 10(11) photons.s(-1).mm(-2), showing no visible damage due to the X-ray exposure.

We have obtained x-ray phase-contrast images with high spatial resolution by using extremely asymmetric Si 111 Bragg diffractions near the critical angle of the total reflection. The x-ray image could be magnified to 294 times in both vertical and horizontal directions. By using this x-ray microscopy system, we have observed clear phase-contrast images of a 0.7-mum-wide gold-line pattern. (C) 2001 American Institute of Physics.

Because of the difficulties of using electron-based techniques in the metalorganic vapor-phase epitaxy (MOVPE) environment, an in situ X-ray diffractometer that combines a goniometer and reactor chamber was developed. Consequent measurements of P-rich InP(001) surface grown by MOVPE show the surface has a (2 x 1) structure. Calculations based on a P-dimer model suggest that this structure is composed of P-dimers whose bonding is parallel to the [(1) over bar 10] direction and indicates indium displacement in the second layer. (C) 2000 Elsevier Science B.V. All rights reserved.

We measure the diffraction peaks of InGaAsP selective metal-organic vapor-phase epitaxial layers on 1.7-mu m-wide InP stripe regions between a pair of SiO2 mask stripes. This is achieved by using an x-ray microbeam with low angular divergence and a narrow energy bandwidth that was produced through two-dimensional condensation of undulator radiation x rays from a synchrotron light source using successive asymmetric diffraction. The lattice strain is investigated by changing the SiO2 mask width from 4 to 40 mu m. The rocking curves reveal clear peak shifts in the InGaAsP layers from the higher angle side to the lower angle side of the InP substrate peaks as the mask width increases. (C) 2000 American Institute of Physics. [S0003- 6951(00)01935-5].

A reconstructed surface of InP (001) substrate, grown by metalorganic vapor phase epitaxy under atmospheric hydrogen environment, is investigated by using grazing incident x-ray diffraction. Fractional-order diffractions of (n/2 m) were observed, showing the existence of a (2 x 1) domain on the surface. Calculations based on the P-dimer model suggest that there are P dimers whose bonding is parallel to the [(1) over bar 10] direction and indium displacement in the second layer. (C) 2000 American Institute of Physics. [S0003-6951(00)02733-9].

We have developed a parallel X-ray microbeam of 7 x 5 mu m(2) in size with a small angular divergence, which aims high-resolution strain measurements in a very local area. The microbeam has been formed by compressing and collimating the X-rays from a third-generation undulator source using successive asymmetric reflections. Using this beam, we have evaluated the strain induced by field oxidation in silicon wafers by rocking curve measurements. We have observed that the lattice constant in the Si region near the oxide film edge is contracted and that in the SiO2/Si region is extended. The difference between these lattice constants is as small as about Delta d/d similar to +/-5 x 10(-6).

An imaging transmission hard X-ray microscope has been constructed at the Hyogo-BL (BL24XU) of SPring-8. It makes use of X-ray phase zone plates (PZP's) made of tantalum as its condenser and objective lenses. The objective PZP has an outermost zone width of 250 nm, which corresponds to the theoretically expected spatial resolution of 300 nm. An experiment was performed at the photon energy of 10keV to check the performance of the microscope. Since a 250 nm line-and-space pattern was clearly resolved, we concluded that the microscope attained a spatial resolution limit better than 500 nm. A few samples were also examined and the feasibility of the microscope was successfully demonstrated.

A novel approximation for calculating the first-order spatial coherence of undulator radiation is presented. Since the far-field approximation is not used in the calculation, it is applicable even in the near-field region. Compared with numerical results based on the first principles, the approximation is proved to be quite reasonable. The spatial coherence measured at the Photon Factory, KEK is analyzed using the formula and the results are found to be consistent with the design value within experimental errors. (C) 2000 Elsevier Science B.V. All rights reserved.

Results of phase-contrast X-ray imaging are presented. The optical system employed consisted of a successive arrangement of horizontal and vertical (+, -) double crystals taking asymmetric Bragg reflection with an asymmetry factor of similar to 0.2. The original beam size was thus expanded in both directions and the field of view actually obtained was similar to 5 x 5 mm(2). Boundary structures in samples were clearly observed with much higher contrast than those obtained in conventional absorption-contrast imaging. Since this method works in real time, it will provide a new X-ray imaging diagnosis technique for in situ observation over a large area of the samples.

The diamond crystals with a (100) or a (111) surface are characterized by the uses of rocking curve measurements, reciprocal lattice mapping and Lang topography method. The full widths at the half maxima of the rocking curves at the X-ray energy of 8.04 keV have been measured to be 6.5 arcsec and 6.3 arcsec for 400 and 111 Bragg reflection, respectively. While the value for 400 reflection is 1.3 times larger than the theoretical value, that for 111 reflection is almost the same as the theoretical one. A sub-peak of about 15 arcsec leaning to the main peak is clearly seen in the reciprocal lattice maps of (100) crystals. No sub-peak can be seen in those of (111) crystal. In addition, some streaky intensity distribution due to a dynamical effect of the X-ray diffraction, being elongated in the radial direction from the reflection point, is clearly seen. This means that crystallinity of(111) planes is more perfect. From the (100) Lang's topographs, it has also been clarified that the diamond crystals include some defect bundles inside the crystals.

Amorphous layers of gallium arsenide (a-GaAs) formed by heavy implantation of silicon ions and crystalline gallium arsenide (c-GaAs) were irradiated with monochromatized X-rays using brilliant synchrotron radiation. Infrared absorption measurements at low temperature for a-GaAs specimens showed that X-rays having an energy larger than the K-binding energy of As atoms created a much larger fraction of Si-Ga and Si-As bondings than in the as-implanted state. On the other hand, from photoluminescence measurements, it was confirmed that X-rays having a smaller energy than either of the K binding energies, enhanced the relaxation of the a-GaAs network, and created some defects in c-GaAs. The mechanism for these structural changes is discussed from the viewpoint of relaxation processes after inner-shell electron excitation by X-rays.

Diamond-like carbon films have been irradiated with x-rays from a synchrotron radiation source. Raman measurements showed that the fraction of tetrahedrally coordinated (sp(3)) bond in the film increased with the increase of x-ray irradiation time, whereas it decreased as the annealing temperature increased. It was confirmed by electron spin resonance measurements that the number of spins did not change by x-ray irradiation. These results indicated that the transition from sp(2) to sp(3) bond takes place by nonthermal Coulomb repulsive rearrangement of atoms after inner-shell electron excitation. (C) 1998 American Vacuum Society. [S0734-2101(98)08804-6].

The first-order spatial (transverse) coherence of synchrotron radiation has been measured using a Young's interferometer at BL28A (a helical-undulator beamline) of the Photon Factory, KEK. The range of the photon energy is about 70–180 eV. The visibility of the fringe was found to depend largely on the electron emittance and the intrinsic photon emittance. In principle, it is possible to gain knowledge of the very small electron emittance, of the order of 10⁻¹⁰ m rad, without disturbing the electron beam in the storage ring.

High-resolution and large diameter condenser Fresnel zone plates were fabricated in a 0.35-mu m-thick Ta layer on an SiN membrane. A newly developed conversion algorithm was applied where sub-field length and position are randamized in order to suppress the evolution of small figures at pattern divided parts such as subfield boundaries in the conventional conversion algorithm. A single layer resist system was adopted to write large diameter, ultra-fine, dense ring patterns. FZPs with the outer-most linewidth of 50 nm was successfully fabricated by applying the subtractive x-ray mask fabrication process.

Three-dimensional images of the near-surface atom arrangement were calculated from two-dimensional photoelectron diffraction data by several imaging algorithms: (i) a basic method with a Fourier transformation at one kinetic energy over k space, considering the phase factor due to the path-length difference; (ii) energy summation of the above results; (iii) Fourier transformation within small k-space windows; and (iv) their combinations. Atomic images produced by these methods from the experimental Si 2p photoelectron diffraction patterns of an Si(001) surface are compared with the crystal geometry. The results show that the energy-summed small-window method, called SWEEP, gives the best images.

Absorption spectra as microspectroscopy taken inside single magnetic domains of nickel have been achieved in the 2p-3d excitation region with a 1 mu m spot of circularly polarized undulator radiation focused by a scanning x-ray microscope. A sample used as demonstration was a deposited nickel layer. It was confirmed that the spectra exhibited the features corresponding to the opposite magnetization of each domain using the fixed circular polarization. This technique can offer element- and domain-specific x-ray magnetic microspectroscopy in a submicrometer scale. (C) 1996 American Institute of Physics.

Two-dimensional band structures of single-crystalline 1T-TaS2 have been directly observed by using a new version of two-dimensional display-type spherical mirror analyzer. The intensity distribution patterns for linearly-polarized synchrotron radiation normally incident on the cleaved surface have shown unusual angular distributions. The non three-fold symmetry is discussed by considering the angular dependence of the dipole transition probability for the s-polarized synchrotron radiation fi om each atomic orbital with particular symmetry, as well as the tight-binding initial state and a free electron like final state. In addition, circular dichroism in angular distribution (CDAD) of the photoemission pattern from the valence band is predicted for 1T-TaS2.

Two-dimensional patterns of angle-resolved photoemission are measured on Kish graphite and 1T-TaS2 for s-polarized synchrotron radiation. Observed symmetry-broken patterns are theoretically discussed. The effect of the dipole selection rules by the s-polarized light is clarified. It is found for the first time that an interference of photoelectron waves from non-equivalent sites provides uneven intensity distribution in different Brillouin zones. The patterns of 1T-TaS2 measured at 40 eV are remarkably different from those at 22 eV, which is explained by the resonant photoemission in the Ta 5 p core excitation region breaking the dipole selection rule due to the direct recombination type Auger transition.

The magnetic circular dichroism of NixPd1-x was measured in the Ni 3p, Pd 4p, Ni 2p, and Pd 3p excitation region. The change in the total magnetic moment and the contribution by orbital moments associated with the constituent atoms were estimated through the obtained spectra. There is a non negligible difference between the data in the Ni 3p-3d excitation region and those in the Ni 2p-3d excitation region, which has been interpreted in terms of atomic and itinerant aspects of the 3d states. It is found that the Ni 2p-3d spectra reflects atomic aspect of the valence band while Ni 3p-3d spectra an itinerant aspect, both of which give complementary information. The orbital moment is found to increase with decreasing x. The result is not in full agreement with the previous result of the band calculation.

The magnetic circular dichroisms (MCD) in the photoabsorptions by Eu, Gd, Tb, Dy, and Ho thin films were measured in the 4d-4f excitation region. The extended MCD signals were observed except for Eu and Gd both in the lower and the higher photon energy regions with the opposite signs, indicating that the interference between the 4d-4f excitation and the 4f-epsilonl excitation is more dominant than the 4f-epsilonl potential barrier effect in heavy rare earths. The observed MCD data are in fair agreement with theoretical calculations except the intensity of the extended MCD and disappearance of some components of the multiplets.