Kazuo Miyamura

Investigation of the initial stage of GaN epitaxial growth on 6H-SiC (0001) at room temperature

We have investigated the initial stage of GaN epitaxial growth on 6H-SiC (0001) at low substrate temperatures by pulsed laser deposition (PLD). We found that GaN grows epitaxially even at room temperature (RT) on atomically flat 6H-SiC (0001) surfaces, which can be explained by the enhanced surface migration of film precursors due to the use of PLD and atomically flat substrates. In situ reflection high-energy election diffraction observations have revealed that GaN films grown at above 300°C proceed in a three-dimensional mode, while those at RT proceed in a layer-by-layer growth mode with atomically flat terraces and steps. The step height turned out to be 1.5nm, which is the same height as the steps on the SiC substrates. This result indicates that the step height on the SiC surface is retained as the GaN grows.

Rod-like Liquid Crystals of Organic Transition Metal Complexes 31: A Reversible Transition between Dimer Smectic E Phase and Monomer Smectic A Phase in the [N,N′-bis(5-alkylsalicylidene) ethylenediaminato nickel(II) Complexes

Abstract It was found that the [N,N′-bis(5-alkylsalicylidene)ethylenediaminato Ni(II) (abbreviated as (Cn-Salen)2Ni: n = 6, 12) complexes show two smectic liquid crystalline phases, SE and SA. The SE ⇆ SA phase transition in the C12-salen)2Ni complex is accompanied by a reversible stretching of the interlayer distances. A dimer SE-monomer SA phase transition can be deduced from this phenomenon.

Monolayer formation and aggregation of nickel(II) complexes coordinated with salen substituted by non-linear alkyl side chains

Abstract In order to investigate the effect of α-methylene groups of alkyl-substituted [Ni(salen)] on the aggregating nature, the monolayers of nickel(II) complexes coordinated with N,N′ -disalicylideneethylenediamine (salen) substituted by propyl, 1-methyl-propyl and 1,1-dimethylpropyl side chains have been prepared at a water–air interface using the Langmuir–Blodgett (LB) method. The π-A isotherm measurement revealed the formation of two different types of monolayers, condensed phase and expanded phase. When the hydrogen atoms of α-methylene groups were totally substituted by the methyl groups, the transition pressure of the expanded phase to the condensed phase decreased considerably from 5.4 to 1.0 mN m −1 , and the critical area of the expanded phase increased by ca. 20%. This observation suggests the presence of CH-π interaction between the α-methylene group and the π-conjugated system in the monolayer state as has been found in the crystalline state.

Aggregation Structure of Quarternary Ammonium Salts of [Ni(dmit)2] Complex in Crystal

Abstract The aggregation structures of [Ni(dmit)2] complex salts of quarternary ammonium with one or two alkyl (C12H25, C18H37) groups are analysed by thermal analysis and x-ray crystallographic analysis. The aggregation structure was found to change drastically by the number of alkyl chains.

Stereochemical Properties of Copper(II) Complexes of (S)-3-Aminohexahydroazepine. Crystal and Molecular Structure of Bromobis[(S)-3-aminohexahydroazepine]copper(II)Perchlorate [CuBr(S-ahaz)2]ClO4

A series of copper(II) complexes of (S)-3-aminohexahydroazepine (abbreviated as S-ahaz) were prepared. The molecular structure of bromobis[(S)-3-aminohexahydroazepine]copper(II) perchlorate, [CuBr(S-ahaz)2]ClO4, was determined using single-crystal X-ray diffraction method. The complex crystallizes is space group P212121 with a=13.449(6), b=17.411(11), c=7.937(2) A, and Z=4. The structure was solved by the direct method and refined by the least squares to R value of 0.068 for 1853 unique reflections. The Cu2+ ion has the square-pyramidal five-coordination geometry with four nitrogen atoms as basal donors and a bromide as an apical donor. The structures of other copper(II) complexes of S-ahaz were assigned on the basis of the above X-ray analysis result, together with electronic spectral and conductivity measurements. The complexes having the formula Cu(S-ahaz)2X(ClO4) (X−=CI−, I−, NCS−, ONO−) were assigned to have square-pyramidal five-coordinated structures. The S-ahaz complexes Cu(S-ahaz)2X2 (X−=Cl−, Br−...

Formation and observation of dimers of a metal complex with long alkyl side chains aligned on a graphite surface

Scanning tunnelling microscope was successfully applied to observe self-assembled molecular images of (bis(5-dodecylsalicylidene)ethylenediaminato)nickel(II) in the form of dimers on highly oriented pyrolytic graphite.

Solvent composition dependence of the voltage generation and the electric pulse formation in the water–nitrobenzene–water liquid membrane system

An experimental set-up consisting of a hollow glass tube and a beaker has been used to form a water–nitrobenzene–water three-phase system in a beaker. This system, with surfactant dissolved in one of the two aqueous phases and picric acid in the organic phase generated electric pulses. The voltage generated between the two aqueous phases was accelerated by reducing the distance between them and was dependent on the concentration ratio of the surfactant and the picric acid. Changes in the mode of the electric pulses were brought about by changing the concentration ratio of the surfactant and the picric acid.

Tunnel Gap Imaging Investigation of Voltage Dependence of Molecular Images Obtained by Scanning Tunneling Microscope

The molecular images obtained by scanning tunneling microscope (STM) exhibit bias voltage dependence, and at low bias voltage, the molecular images disappear. This voltage dependence of STM molecular images is investigated by the tunnel gap imaging (TGI) technique using STM equipment. TGI is a technique that maps out the vertical variation of the tunnel current by measuring the tunnel gap width dependence of the tunnel current at each pixel. It is shown that the tip is repelled from the surface by 5-6 nm when the bias voltage is increased by about 1 V. Marked increase in the apparent corrugation accompanies this phenomenon. The mechanism of STM molecular image formation is discussed in terms of the vertical distribution of the local density of states (LDOS).

Barrier Height Imaging Investigation of Liquid Crystal Molecules Adsorbed on Graphite

The barrier height imaging technique was applied to a graphite surface covered with liquid crystal molecules. Barrier height images of the molecules were found to exhibit better image quality than the scanning tunneling microscope (STM) images. Under different conditions, images of underlying graphite were obtained instead of molecular images, in both STM and barrier height images. It was also found that the barrier height image and the simultaneously obtained STM image of adsorbed molecules were reversed in contrast while those of the underlying substrate graphite were similar. The reason for this difference was discussed in relation to the mechanism of molecular image formation.

Tunnel Gap Imaging Study of Highly Oriented Pyrolytic Graphite Using Scanning Tunneling Microscope

An STM system capable of measuring the tunnel gap separation (s) dependence of tunnel current (I), i.e., the I-s characteristics, was constructed. The I-s characteristics were successfully measured by sweeping the set current, instead of modulating the tip position. It was found that the tunnel current could be detected over a separation range of 1 nm. Furthermore, a new imaging technique, tunnel gap imaging, which maps out the lateral distribution of the I-s characteristics, is proposed and realised.