Yoshiyuki Higashigaki

Epitaxial growth of β-SiC single crystals by successive two-step CVD

Abstract Single-crystalline β-SiC films are grown on Si (111) substrates by chemical vapor deposition (CVD) using SiH 2 Cl 2 and C 3 H 8 gases. In order to achieve the heteroepitaxial growth with large lattice mismatch, a very thin layer of polycrystalline SiC is at first deposited on the substrate surface at relatively low temperature. Then, SiC single crystal films are successively grown on the thin SiC layers for 2 to 6 h at higher temperature. SiC films with the thicknesses of 0.6–4.5 μm are obtained uniformly on the Si substrate (15 × 15 mm 2 ). X-ray diffraction and reflection electron diffraction measurements reveal an excellent crystal quality and the same crystallographic orientation as the substrate.

Three types of aggregates of spiropyran with long and short hydrophobic alkyl chains

Abstract The spiropyran derivative 1′-octadecyl-3′,3′-dimethyl-6-nitro-8-ethoxymethyl-spiro[2H-1-benzopyran-2,2′-indoline] (SP1802) has been synthesized and its photochromic and aggregate forming properties in both monolayer films at the air-water interface and in Langmuir-Blodgett (LB) films have been investigated. The UV-induced photomerocyamine (PMC) isomer forms J-aggregates ( λ max = 655 nm ) on the water surface when compressed. In the LB deposition process a rapid transfer rate induces a change to the brickwork-like arrangement of the chromophores in the J-aggregates, and H-aggregates ( λ max = 495 nm ) and I (intermediate)-aggregates ( λ max = 575 nm ) form depending on the surface pretreatment of the substrate. Hydrophobic substrates treated with trimethylchlorosilane, yield a change to the H-aggregates whilst substrates precoated with multilayers of arachidic acid produce a change to the I-aggregates.

Low temperature growth of pyrolytic carbon with well-ordered graphite structure by chemical vapour deposition methods

Abstract Carbon films with well-ordered graphite structure were successfully deposited on a quartz substrate by thermal decomposition of benzene gas at 1000°C. The improvement in the degree of preferred orientation to the substrate surface was verified by reflection high energy electron diffraction observations. Such good crystallinity of the films was shown to be responsible for high in-plane electrical conductivity ( σ | = 2.2 × 10 3 Ω -1 cm -1 ). Investigations concerning the film properties and their dependence on the deposition conditions will be described.

Structural Properties of Some Cyanoethenes with Optical Nonlinearity

An α-cyanostilbene crystal showing optical nonlinearity was examined to be compared with a non-optically active crystal, with emphasis on the structural aspect. It was suggested that the introduction of bulky substituents such dimethylamino and methoxy groups into the cyanostyrene conjugation system was effective to get macroscopic optical nonlinearity, based on the chemical synthesis and structural analysis. It was also stressed that the quadrupole interaction in α-cyanostilbenes was one of the important factors responsible for a nonsymmetric molecular arrangement for the second order optical nonlinearity.

Method for the production of carbon films having an oriented graphite structure

A method for preparing pyrolytic carbon film having a highly ordered graphite structure which comprises introducing an aromatic compound not having a condensed ring, together with a carrier gas into a reaction chamber, thermally decomposing the aromatic compound at a temperature up to 1,000° C., and depositing the carbon film onto a single-crystalline substrate.

The nonlinear optical characteristic of α-cyano-(3-methoxy-4-hydroxy-5-bromo)methylcinnamate (CMHB)

We have synthesized the nonlinear material α-cyano-(3-methoxy-4-hydroxy-5-bromo)methylcinnamate (CMHB). CMHB has been grown from solution evaporating method. CMHB belongs to the Triclinic system, and its space group is P1. The unit cell dimensions are: a=4.551 A, b=11.085 A, c=12.714 A with α=101.89°, β=98.64°, γ=90.85°. The powder second harmonic generation of CMHB is 8 times higher than that of urea and the cutoff wavelength is 355 nm (in 1,4-dioxen).