Tetsuo Kado

Preparation and structural analysis of nickel/nickel oxide multilayers

Metal/oxide multilayers composed of nickel and nickel oxide were prepared on silicon, fused quartz, and sapphire substrates in an ultrahigh vacuum deposition system using two different methods for growing oxide layers: an oxidation method of metal layering using pulsed oxygen molecular beam, and an evaporation method of NiO with an electron beam evaporator. With x‐ray diffraction and calculations using dynamical theory of x‐ray reflection, the films prepared via oxidation with more than 60 pulses of oxygen beam at 298 K, and the films prepared by evaporation below 473 K revealed multilayers of Ni/NiOx with artificial periodicity. Multilayers prepared with the oxidation method on silicon and fused quartz have homogeneous bilayers composed of polycrystalline Ni and amorphous‐like NiO. In contrast, multilayers prepared by the evaporation method on a sapphire substrate are structurally graded, with layer structures which change gradually from single crystals (1st layer) to polycrystals (last layer).

Characteristics of Chromium Oxycarbide Thin Film Prepared by Plasma‐Assisted CVD Method

The authors describe thin films containing chromium compound prepared onto SUS 304 stainless steel and slide glass substrates by plasma decomposition of hexacarbonylchromium with hydrogen carrier gas. The chemical composition of the films was identified as chromium oxycarbide (Cr/sub 2/CO) by XPS measurements, and the structure of Cr/sub 2/CO was revealed as a face-centered cubic structure by x-ray diffraction experiments. Vickers hardness and the anodic polarization current density of the films were measured in order to investigate the properties of corrosion resistance. As a result, the Cr/sub 2/CO film was found to have one of the best characteristics for coating the material to resist surface corrosion.

Structural and Mechanical Properties of Cr2CO Films

Thin films of chromium oxycarbide(Cr2CO) were prepared on SUS 304 stainless steel and slide glass by plasma decomposition of hexacarbonylchromium with hydrogen carrier gas. The structure of the film was investigated in detail by X-ray diffraction. It was found that the structure of Cr2CO was fcc and that the (111) plane was highly oriented on the substrate surface. The characteristics of Vickers hardness, electric conductivity and deposition rate strongly correlated to the X-ray intensity of the particular Bragg scattering.

Ti/MgO superlattices epitaxially grown on sapphire (00.1) and MgO(001) substrates

Epitaxial metal/insulator superlattices composed of Ti and MgO have been prepared on MgO(001) buffer layers grown on MgO(001) substrates and MgO(111) buffer layers grown on sapphire (00.1) substrates by electron beam evaporation in ultrahigh vacuum. 1–4‐nm‐thick Ti layers and 1–2‐nm‐thick MgO layers have been grown alternatively for 20 periods on the buffer layers at 273 K and at a growth rate below 0.02 nm/s. The reflection high energy electron diffraction and x‐ray diffraction measurements reveal that the crystal structures of Ti in the superlattices grown on MgO(001) and on sapphire (00.1) substrates are face‐centered tetragonal structure and hexagonal closed‐packed structure, respectively.

Epitaxial superlattice of Ag/NiO prepared on MgO(001)

Abstract Films composed of alternating ultrathin layers of metal Ag and oxide NiO have been prepared by electron beam evaporation in ultrahigh vacuum. The films were grown on a MgO(001) substrate at 273 K and at a growth rate below 0.1 nm/s. The films were epitaxially grown, as determined by in situ reflection high-energy electron diffraction patterns. The artificial periodicity in the films was confirmed by X-ray diffraction and cross-sectional high-resolution transmission electron microscopy. The films were concluded to be a new epitaxial superlattice composed of metal and oxide.

Epitaxial superlattices of TiAg alloy/MgO grown on MgO(001)

High crystalline quality epitaxial metal/insulator superlattices composed of Ti1−xAgx (0.03<x<0.06) and MgO have been grown on MgO(001) substrates at 273 K by electron beam evaporation in ultrahigh vacuum. X‐ray diffraction measurements and cross‐sectional high‐resolution transmission electron microscopy measurements revealed that the crystal structures of the TiAg alloy and MgO in the superlattices were tetragonal and that the superlattices were so‐called strained‐layer superlattices. The x‐ray rocking curve was measured around one of satellite peaks in the middle angle range, and showed the full width at half‐maximum of the curve was 0.04°–0.05°.

Preparation and structural analysis of an Ag/NiO strained‐layer superlattice

A new superlattice composed of Ag and NiO has been grown epitaxially on MgO(001) substrates by electron beam evaporation in ultrahigh vacuum. The samples were characterized by x‐ray diffraction and cross‐sectional high resolution transmission electron microscopy. Two component materials have different crystal structures; Ag has face‐centered cubic structure and NiO has NaCl‐type structure. Lattice mismatch between them is about 2%, and hence the superlattice should be classified as a so‐called strained‐layer superlattice. As a result of the structural analysis, it is estimated that Ag has face‐centered tetragonal structure with the axial ratio c/a of 0.98–0.99 and that NiO has a tetragonally distorted NaCl‐type structure with the ratio c/a of 1.04–1.05 in the superlattices, where direction of c‐ax is parallel to the growth direction.