Cubic coil system composed of three sets of cubic triple coils to produce wide area 0.66% uniform magnetic field in any direction.

A cubic coil system, which combines three sets of cubic triple square coils orthogonal to each other, is proposed, constructed, and tested. This coil system can generate a 0.66% (=±0.33%) uniform magnetic field in any direction over a large region of ∼2 m, although there is some ripple. This system has the advantages of easy assembly, self-standing, and easy access to internal instruments. In one set of cubic triple square coils, the outer two square coils form a cube, and the middle square coil is located at the center of the cube. The number of turns in the center square coil is proposed to be 0.6 times that of the outer square coil.

Origin of Unexpected Ir3+ in a Superconducting Candidate Sr2IrO4 System Analyzed by Photoelectron Holography.

The reason for the absence of superconductivity in Sr2IrO4 was estimated by photoelectron spectra and photoelectron holograms. The analysis of the La photoelectron hologram concluded that La atoms are substituted to Sr sites. Two O 1s peaks were observed and were identified as the oxygens in the IrO2 and SrO planes by photoelectron holography and density functional theory (DFT) calculations. In the Ir 4f spectrum of Sr2IrO4, an unexpected Ir3+ peak was observed as much as 50% of all of the Ir. The photoelectron hologram of Ir3+ showed a displacement of about 0.15 Å. This displacement is thought to be due to the oxygen vacancies in the IrO2 plane. These oxygen vacancies and the associated local displacement of the atoms might inhibit superconductivity in spite of sufficient electron doping.

Variable-deceleration-ratio wide-acceptance-angle electrostatic lens for two-dimensional angular and energy analysis.

Variable-deceleration-ratio wide-acceptance-angle electrostatic lens (VD-WAAEL) is proposed as a potential technique for two-dimensional angular and energy analysis. The basic features of the lens are studied using the charge simulation method and ray tracing calculation. The lens uses an ellipsoidal mesh electrode and allows a wide acceptance angle of ±50°. Two possible applications of the VD-WAAEL are discussed. One is a simple combination of the VD-WAAEL-projection-lens, in which an aperture is used for energy analysis. The other is a combination of the VD-WAAEL with a conventional electron spectrometer, which is responsible for obtaining higher energy resolution. The former is discussed in detail and the latter is described briefly. While the ray tracing calculation is only for the case of an ideal mesh, a note on the disturbing effect of mesh holes is presented. The best possible energy resolution of the simple VD-WAAEL-projection-lens analyzer seems to be around 1/1000, given a fine mesh electrode to suppress the disturbing effect of mesh holes.

Noble Metal Nanocluster Formation in Epitaxial Perovskite Thin Films.

We studied the synthesis of nanocomposite materials consisting of noble metal clusters embedded in an oxide semiconductor matrix. The embedded nanostructures form in a simple self-organized single-step growth process. The primary interest is in developing materials for photo-electrochemical energy conversion where spatially inhomogeneous band structures can enhance photogenerated charge separation and carrier extraction from a semiconductor. We show that spontaneous segregation of metallic Ir occurs during the initial growth of an Ir:SrTiO3 thin film. Cross-sectional transmission electron microscopy suggests that the nanoscale Ir clusters are epitaxial with the host lattice, and their presence is not detectable by surface morphology measurements.

Photoelectron Holographic Atomic Arrangement Imaging of Cleaved Bimetal-intercalated Graphite Superconductor Surface.

From the C 1s and K 2p photoelectron holograms, we directly reconstructed atomic images of the cleaved surface of a bimetal-intercalated graphite superconductor, (Ca, K)C8, which differed substantially from the expected bulk crystal structure based on x-ray diffraction (XRD) measurements. Graphene atomic images were collected in the in-plane cross sections of the layers 3.3 Å and 5.7 Å above the photoelectron emitter C atom and the stacking structures were determined as AB- and AA-type, respectively. The intercalant metal atom layer was found between two AA-stacked graphenes. The K atomic image revealing 2 × 2 periodicity, occupying every second centre site of C hexagonal columns, was reconstructed, and the Ca 2p peak intensity in the photoelectron spectra of (Ca, K)C8 from the cleaved surface was less than a few hundredths of the K 2p peak intensity. These observations indicated that cleavage preferentially occurs at the KC8 layers containing no Ca atoms.

Correction to "Filtering Chromatic Aberration for Wide Acceptance Angle Electrostatic Lenses II-Experimental Evaluation and Software-Based Imaging Energy Analyzer".

In [1], the following support information should have been included in the first footnote.

Filtering Chromatic Aberration for Wide Acceptance Angle Electrostatic Lenses II--Experimental Evaluation and Software-Based Imaging Energy Analyzer.

Here, the experimental results of the method of filtering the effect of chromatic aberration for wide acceptance angle electrostatic lens-based system are described. This method can eliminate the effect of chromatic aberration from the images of a measured spectral image sequence by determining and removing the effect of higher and lower kinetic energy electrons on each different energy image, which leads to significant improvement of image and spectral quality. The method is based on the numerical solution of a large system of linear equations and equivalent with a multivariate strongly nonlinear deconvolution method. A matrix whose elements describe the strongly nonlinear chromatic aberration-related transmission function of the lens system acts on the vector of the ordered pixels of the distortion free spectral image sequence, and produces the vector of the ordered pixels of the measured spectral image sequence. Since the method can be applied not only on 2D real- and $k$ -space diffraction images, but also along a third dimension of the image sequence that is along the optical or in the 3D parameter space, the energy axis, it functions as a software-based imaging energy analyzer (SBIEA). It can also be applied in cases of light or other type of optics for different optical aberrations and distortions. In case of electron optics, the SBIEA method makes possible the spectral imaging without the application of any other energy filter. It is notable that this method also eliminates the disturbing background significantly in the present investigated case of reflection electron energy loss spectra. It eliminates the instrumental effects and makes possible to measure the real physical processes better.

Selective detection of angular-momentum-polarized Auger electrons by atomic stereography.

When a core level is excited by circularly polarized light, the angular momentum of light is transferred to the emitted photoelectron, which can be confirmed by the parallax shift of the forward focusing peak (FFP) direction in a stereograph of atomic arrangement. No angular momentum has been believed to be transferred to normal Auger electrons resulting from the decay process filling core hole after photoelectron ejection. We succeeded in detecting a non-negligible circular dichroism contrast in a normal Auger electron diffraction from a nonmagnetic Cu(001) surface far off from the absorption threshold. Moreover, we detected angular-momentum-polarized Cu L(3)M(4,5)M(4,5) Auger electrons at the L(3) absorption threshold, where the excited core electron is trapped at the conduction band. From the kinetic energy dependence of the Auger electron FFP parallax shift, we found that the angular momentum is transferred to the Auger electron most effectively in the case of the (1)S(0) two-hole creation.

Structure and magnetic properties of mono- and bi-layer graphene films on ultraprecision figured 4H-SiC(0001) surfaces.

Monolayer and bilayer graphene films with a few hundred nm domain size were grown on ultraprecision figured 4H-SiC(0001) on-axis and 8 degrees -off surfaces by annealing in ultra-high vacuum. Using X-ray photoelectron spectroscopy (XPS), atomic force microscopy, reflection high-energy electron diffraction, low-energy electron diffraction (LEED), Raman spectroscopy, and scanning tunneling microscopy, we investigated the structure, number of graphene layers, and chemical bonding of the graphene surfaces. Moreover, the magnetic property of the monolayer graphene was studied using in-situ surface magneto-optic Kerr effect at 40 K. LEED spots intensity distribution and XPS spectra for monolayer and bilayer graphene films could become an obvious and accurate fingerprint for the determination of graphene film thickness on SiC surface.

Development of the hard-X-ray angle resolved X-ray photoemission spectrometer for laboratory use.

This article reports development of a practical laboratory hard X-ray photoelectron spectroscopy (HXPS) system by combining a focused monochromatic Cr K(alpha) X-ray source, a wide angle acceptance objective lens and a high kinetic energy electron analyzer. The Cr K(alpha) source consists of a Cr target, a 15 kV focused electron gun, and a compact bent crystal monochromator. The X-ray spot size is variable from 10 microm (1.25 W) to 200 microm (50 W). A wide acceptance angle objective lens is installed in front of a hemispherical analyzer. The total resolution of 0.53 eV was obtained by Au Fermi-edge measurements. Angle acceptance of +/-35 degrees with angle resolution of 0.5 degrees was achieved by measuring Au 3d(5/2) peak through a hemicylinder multi-slit on an Au thin strip, in angle resolution mode. As the examples, silicon based multilayer thin films were used for showing the possibilities of deeper (larger) detection depth with the designed system.

Atomic-layer resolved magnetic and electronic structure analysis of ni thin film on a Cu(001) surface by diffraction spectroscopy.

Up until now there has been no direct method for detecting the electronic and magnetic structure of each atomic layer at the surface, which is an essential analysis technique for nanotechnology. For this purpose, we have developed a new method, diffraction spectroscopy, based on the photon energy dependence of the angular distribution of Auger electron emission. We have applied this method to analyze the magnetic structure of a Ni ultrathin film on a Cu(001) surface around the spin reorientation transition. Atomic-layer resolved x-ray absorption and magnetic circular dichroism spectra were obtained. Surface and interior core-level shifts and magnetic moments are determined for each atomic layer individually.

Approach for simultaneous measurement of two-dimensional angular distribution of charged particles. III. Fine focusing of wide-angle beams in multiple lens systems.

This paper provides a way of focusing wide-angle charged-particle beams in multiple lens systems. In previous papers [H. Matsuda, Phys. Rev. E 71, 066503 (2005); 74, 036501 (2006)], it was shown that an ellipsoidal mesh, combined with electrostatic lenses, enables correction of spherical aberration over wide acceptance angles up to +/-60 degrees . In this paper, practical situations where ordinary electron lenses are arranged behind the wide-angle electrostatic lenses are taken into account using ray tracing calculation. For practical realization of the wide-angle lens systems, the acceptance angle is set to +/-50 degrees . We note that the output beams of the wide-angle electrostatic lenses have somewhat large divergence angles which cause unacceptable or non-negligible spherical aberration in additional lenses. A solution to this problem is presented showing that lens combinations to cancel spherical aberration are available, whereby wide-angle charged-particle beams can be finely focused with considerably reduced divergence angles less than +/-5 degrees .

Approach for simultaneous measurement of two-dimensional angular distribution of charged particles. II. Deceleration and focusing of wide-angle beams using a curved mesh lens.

Recently, it was shown that using an ellipsoidal mesh in an einzel-type lens, spherical aberration can be corrected over a wide acceptance angle of up to 120 degrees. The present paper creates the possibility for beam analysis by achieving dramatic improvements in deceleration lens capabilities. This provides a scheme for simultaneous angular distribution measurement suitable for application to high-energy charged-particle beams up to around 10 keV. We consider the behavior of wide-angle charged-particle beams in electrostatic fields given by simple solutions of the Laplace equation, starting with a discussion on a spherically symmetric deceleration field. A beam focusing over a wide acceptance angle of 100 degrees is found in a special spherically symmetric field. However, in many cases of the spherically symmetric field, focusing of wide-angle beams is obstructed by the presence of spherical aberration. We show that the spherical aberration can be corrected by two kinds of deformation of the spherically symmetric field, a deformation of the field under a spherical boundary condition and an ellipsoidal deformation of the field. We study practical realization of such fields under the use of a few electrodes and a curved mesh (spherical or ellipsoidal mesh). Some variations of the arrangement of electrodes are considered, and simple designs of deceleration lenses with wide acceptance angles of up to 120 degrees are obtained. Here fine focusing of wide-angle beams can be achieved in a three-electrode deceleration lens with an ellipsoidal mesh.

Visualization of in-plane dispersion of hole subbands by photoelectron spectroscopy.

The in-plane dispersion of the hole subband (HSB) in a Si quantum well is obtained for the first time by applying angle-resolved photoemission spectroscopy and surface science techniques. The entire shape of the HSB over a wide ranged wave vector, including admixing of heavy and light hole subbands around the crossing point and the camelback structure inducing negative effective mass, is visualized directly. Energy separations between the subbands are quantitatively explained.