Kazunobu Hayakawa

Scanning Electron Microscope Observation of Magnetic Domains Using Spin-Polarized Secondary Electrons

A new method for observing magnetic domain structures with a scanning electron microscope has been developed in which the image is the result of spin polarization of secondary electrons. With this method the domain structures on an iron (001) surface have been observed. At present, spatial resolution is not less than 10 µm, but can be expected to be reduced to far less than that of both conventional electron microscopic and optical reflection methods.

Observation of Surface Micro-Structures by Micro-Probe Reflection High-Energy Electron Diffraction

A new micro-probe reflection high-energy electron diffraction technique has been developed for observing micro-structures on crystal surfaces. In this technique, an electron beam of diameter 20 nm at a beam current of 8 nA and a beam angular divergence of 2 mrad has been achieved by using a field emission gun, making it possible to obtain bright, sharp diffraction patterns from surface micro-areas. A diffraction spot on a fluorescent screen is focused on an apperture by an optical lens; and part of the intensity is used as a signal to produce a scanning electron microscope image. This image is very sensitive to changes in surface crystallographic orientation, and can show areas in which the orientation change is of the order of 0.1 mrad. When the technique was used to observe Si(111) surfaces and metal-deposited Si(111) surfaces, image contrasts caused by screw dislocations, atomic steps and domain structures on the surfaces were obtained.

Observation of magnetic domains with spin‐polarized secondary electrons

Magnetic domain structure on a silicon iron (001) surface has been observed using a new scanning electron microscope (SEM), in which image contrast was obtained by using spin polarization of secondary electrons. From this image and an absorption current image of the same area, it has been confirmed that the domain structure image is not influenced by surface morphology. This represents an improvement over conventional domain structure observation methods. This new SEM will be greatly improved also as for the resolving power compared to conventional reflection methods, when used in conjunction with a proper field emission gun.

Magnetic domains of permalloy films for magnetic recording thin film heads observed by spin-polarized SEM

The domain structures of cores patterned in thin film heads for disk drive systems were investigated by using spin-polarized SEM. This method made it possible to determine the direction of the magnetization at the domains and domain walls in magnetic cores accurately. Domain structures in the track width, as small as 10 μ m could be observed. Domain structure could also be observed at the tapering area of a thin film head. It was found that the triangular domains without the closure domains are located at the edge of the magnetic core in single- and six-layered permalloy films in some cases. Such a domain structure was regarded as causing the wiggles in the read-out waveforms.

Domain observation with spin‐polarized secondary electrons (invited)

A new method for observing magnetic domain structures with a scanning electron microscope has been realized in which the image video signal is the spin polarization of secondary electrons. Examples of domain structure images are presented and the potential of this method is discussed.

Observation of Si(111) and gold-deposited Si(111) surfaces using micro-probe reflection high-energy electron diffraction

Abstract Observations of clean Si(111) and gold-deposited Si(111) surfaces have been performed using micro-probe reflection high-energy electron diffraction. It was found that many atomic steps on a Si(111) surface run in nearly the same direction, about 9° off the [112] direction. When gold was deposited on this surface at a substrate temperature of about 800°C, 5 × 1, diffuse √3 × √3 R 30°, sharp √3 × √3 R 30° structures and Au clusters appeared on the surface with continuation of the deposition. During the deposition process, it was found that one kind of Si(111) 5 × 1 Au domain grew selectively along these atomic steps and nearly covered the entire surface. A phenomenon of gold clusters moving during the deposition was also observed. These clusters all moved in nearly the same direction so as to climb the atomic steps.

Micro-Probe Reflection High-Energy Electron Diffraction Technique. : I. Determination of Crystallographic Orientations of Polycrystal-Silicon Surfaces

A micro-probe reflection high-energy electron diffraction (RHEED) apparatus including an electron gun with a probe size of 0.1 µm operated under ultrahigh vacuum, has been constructed. This makes it possible to obtain bright, sharp diffraction patterns from micro-areas of clean surfaces, and to take RHEED-microscope images of crystal surfaces. Using this apparatus, a technique for determining the crystallographic orientations of surface micro-areas within an accuracy of ±1° has been developed. This is done by analyzing Kikuchi patterns emitted at low angles, and spatial distributions having various crystallographic orientations are obtained by taking RHEED-microscope images. From the results of applying this technique to polycrystal-Silicon surfaces, it is found that it is very useful in determining the crystallographic orientations of surface micro-areas.

Variation of emission yield of X-rays from crystals with diffraction condition of exciting electrons

The X-ray intensity of Zn Kα radiation emitted from clean cleavage surfaces (110) of zincblende crystals excited by fast electrons, which impinge on the surfaces in the same way as in ordinary electron diffraction experiments, was measured under various diffraction conditions of exciting electrons. The electron energy was about 30 keV. It was found that the X-ray intensity decreases at Bragg conditions by about 10–20%, in an asymmetric way with respect to the glancing angle of the electrons. Some of features of such an anomaly in X-ray intensity have been discussed on the basis of a two-wave dynamical theory of electron diffraction taking account of the phenomenological absorption.

A high-speed X-ray topography camera for use with synchrotron radiation at the photon factory

Abstract A detailed description of the high-speed X-ray topography camera designed for the vertical wiggler beam line at the Photon Factory is presented. The camera has been successfully operated with a white beam from a normal dipole magnet beam line since June 1982. The flexibility of the camera is sufficiently large to meet various user requirements. Some of its characteristic features are as follows: it has two TV detector arms providing a view coverage of 50° upwards and 30° downwards from the horizontal plane. The goniometer can support a load of 30 kg, to mount specimen environmental conditioners such as magnets and cryostats, while it can rotate with a precision of 2″ of arc over a full circle. The entire camera is placed on a special movable carriage to enable a simple and rapid interchange between a white beam outlet and a monochromatic one. Some 20 different samples and more than 20 people were involved both in commissioning the instrument and in the preliminary experiments, using about 900 h of machine time.

Surface Crystal Structure of Magnetite Fe3O4(110)

The surface crystal structure of magnetite Fe3O4(110) was studied by low-energy electron diffraction (LEED). A clean surface was obtained after sputtering and annealing at 840 K. The clear LEED patterns show fractional order spots corresponding to a (3×1) surface reconstruction with missing spots. The missing spots indicate a glide plane symmetry of the (3×1) surface. Moreover, the LEED patterns have two-fold rotational symmetry, the surface structure should be p2mg-(3×1) or double domain of p1g1-(3×1). The same glide plane symmetry of the reconstructed surface structure and the ideal surface structure of Fe3O4(110) shows a strong relation between surface and bulk structures. We propose one possible model that corresponds to the p2mg-(3×1).