Kouichi Nishikawa

Atomic force microscope study of thin‐plate martensites in an Fe–Ni–C alloy

Morphology and accommodation of thin‐plate martensites in an Fe–Ni–C alloy have been investigated with atomic force microscopy (AFM). The quantitative observation of surface relieves made it possible to determine the kinds of thin‐plate martensite variants by combining with single‐face trace analysis. The martensites keep complementary configuration of variants in order to make the overall strain minimize. Strain distribution induced by the martensite formation in the parent phase was calculated using the height of the surface relief obtained by AFM observation and it was found that a highly strained region exists near the front of the martensite.

Chiral and collinear ordering in a distorted triangular antiferromagnet

Magnetization, specific heat, and neutron diffraction measurements are used to map out the entire magnetic phase diagram of KFe(MoO4)2. This stacked triangular antiferromagnet is structurally similar to the famous multiferroic system RbFe(MoO4)2. Because of an additional small crystallographic distortion, it contains two sets of inequivalent distorted magnetic triangular lattices. As a result, the spin network breaks down into two intercalated yet almost independent magnetic subsystems. One is a collinear antiferromagnet that shows a simple spin-flop behavior in applied magnetic fields. The other is a helimagnet that instead goes through a series of exotic commensurate-incommensurate phase transformations. In the various phases one observes either true three-dimensional or unconventional quasi-two-dimensional ordering.

Structure and properties of MBE-grown Pt/Co multilayer, Pt/Cu doublelayer, Co/Cu doublelayer, Pt film and Cu film on Si(111)-(7×7) substrate

Abstract Crystal growth mode and surface topography of a Pt/Co multilayer showing perpendicular magnetic anisotropy have been investigated by RHEED and AFM. Electric conductivity of the various films were measured and the interface effect in the electric conductivity of the multilayer is discussed.

Topography and crystallography of a Pt film on a Cu buffer layer and a Si(111)(7×7) substrate

Abstract The topography and crystallography of a Pt film on a Cu buffer layer and a Si(111)(7 × 7) substrate have been investigated. A crystallographic analysis of the Pt film, the Cu buffer layer and the Si substrate has been made by RHEED. Pt and Cu grew epitaxially and the orientational relationship was determined to be Pt(111) 2 > ⋎ Cu(111) 2 > ⋎ Si(111) 1 0 >. The growth of the Pt film on the Cu buffer layer was found to be pseudomorphic. An STM study showed that a number of truncated triangular pyramids of Pt were formed all over the surface of the Pt film on the Cu buffer layer and the Si substrate. The characteristics of these truncated triangular pyramids of Pt are described.

Dependence of electrical resistivity on surface topography of MBE-grown Pt film

Surface topography of MBE-grown Pt film was investigated with scanning tunneling microscopy. On the other hand, electrical resistivity of the Pt film in Pt/Cu/Si specimen was measured using a proposed analytical model. Comparing the electrical resistivity change with the surface topography change, dependence of electrical resistivity on surface topography was clearly demonstrated.

Inheritance of Crystal Structure in Cu/Co and Co/Cu Bilayers Grown on MgO(100) Substrate

Bilayers and single layers composed of Co and Cu were formed on MgO(100) substrates as the fundamental unit of the superlattice of Cu and Co. The crystal structure of their films was investigated, with increasing layer thickness of each element, by reflection high-energy electron diffraction observation and X-ray diffraction analysis. If Cu is deposited on MgO(100) first, Cu has the fcc structure and subsequently deposited Co has a metastable fcc structure which is inherited from the crystal structure of the underlying Cu. Cu on hcp-Co has a metastable hcp structure for thin Cu which is inherited from the crystal structure of the underlying Co. The structure of the Cu changes to fcc with increasing Cu layer thickness and the Cu is released from the influence of the substrate.

Scanning Tunneling Microscope and Atomic Force Microscope Observation of Topography of Molecular-Beam-Epitaxy-Grown Pt Films on Cu Buffer Layer and Si(111)-(7×7) Substrate

Topography of Pt films on a Cu buffer layer and Si(111)-(7×7) substrate has been observed by use of scanning tunneling microscopy (STM) and atomic force microscopy (AFM). Changes in topography with increasing thickness of the Pt film are described. Topography of a Cu buffer layer is also described. The existence of two kinds of bands, due to the off-angle of the Si substrate, is shown. As microstructures within the bands, Pt films have a dendritic structure in the early stages of the increase of Pt film thickness, and in the later stages, a number of truncated triangular pyramids of Pt are formed all over the surface of the Pt film.

Epitaxy of Co/Cu and Cu/Co bilayers on MgO(111)

Abstract Bilayers composed of Co and Cu were prepared on MgO(111) substrates as a fundamental unit of the superlattice of Cu and Co; the dependence of the crystal structure of each elemental layer on the thickness was investigated by reflection high-energy electron diffraction (RHEED) observation and X-ray diffraction (XRD) analysis. When Co was deposited first on MgO(111), it exhibited an f.c.c. structure for layers up to 30 nm thick and changed to an h.c.p. structure with increasing Co thickness; subsequently deposited Cu exhibited an f.c.c. structure regardless of the crystal structure of the underlying Co (f.c.c. or h.c.p.). Cu on MgO(111) had an f.c.c. structure, and Co on f.c.c-Cu/MgO(111) exhibited a mixed structure of f.c.c. and h.c.p. phases for a 5 nm thick layer and an h.c.p. structure for a 100 nm thick layer.

Scanning Tunneling Microscopy and Atomic Force Microscopy Study on Interface between Molecular-Beam-Grown Pt Film and Si (111) Substrate

A method of observing interfaces using scanning tunneling microscopy and atomic force microscopy is proposed, and the method is applied to observe interfaces between Pt film and Si(111) substrate, and the Pt/Si interface topography is clearly presented. Microstructures of interface such as band structure, island structure and netlike structure are described in detail. Finally, the reaction path at Pt/Si interface is discussed.

Quantitative analysis of individual atom images in FIM of an ordered Ni4Mo alloy

Quantitative measurements of the position and intensity of individual atom images in field ion microscopy of an ordered Ni4Mo alloy were made successfully. The accuracy of the atom positions in the image was investigated. Intensity distributions especially for low intensity regions around individual atoms were demonstrated successfully by both contour maps and a perspective view. The effects of the geometry and surrounding atoms were discussed.