Satoshi Irie

Point-on-line coincidence in epitaxial growth of CuPcCl16 on graphite

Abstract Epitaxial growth of perchloro-copper-phthalocyanine (CuPcCl 16 ) on graphite was studied by STM and TEM. The crystals grew epitaxially with two slightly different orientations on the graphite surface. The corresponding orientations were also observed in a monolayer of CuPcCl 16 by STM. By detailed analysis of the moire-like pattern in the STM images, these orientations are interpreted as being consistent with a ‘point-on-line coincidence’ epitaxy. In order to realize the exact point-on-line coincidence for the respective orientation, the unit cell dimensions of the monolayer were slightly distorted at each orientation, although they are almost the same as the monoclinic structure of the thin film determined by TEM.

Monolayer and bilayer formation of 17,19-dotetracontadiyne at a liquid/solid interface

Monolayer and bilayer of 17,19-dotetracontadiyne (DTDY) on a graphite substrate were studied by scanning tunneling microscopy at a liquid solid interface of phenyloctane solution. The orientation of the layers was examined with respect to the highly oriented pyrolitic graphite. The first layer grew very quickly with many small domains some tens of nm in diameter, and the alkyl chains of the molecule in each domain align epitaxially along the a g -axis of graphite. When the solution remains at room temperature, the second layer of DTDY grew epitaxially on the first layer and the domain size was much larger than that of the first layer.

A scanning tunneling microscopy study on the monolayer epitaxy of [cyano(ethoxycarbonyl) methylene]-2-ylidene-4,5-dimethyl-1,3-dithiole on graphite and its dynamic feature

The monolayer film of [cyano(ethoxycarbonyl)methylene]-2-ylidene-4,5-dimethyl-1,3-dithiole (CEMYDD) vacuum-deposited on a (0001) graphite surface was investigated by scanning tunneling microscopy (STM). High-resolution STM images showed that all of the molecules formed the same two-dimensional unit cell in each domain and that the unit cell was almost equivalent to that in the (011) plane of the second-harmonic-generation active β-form crystal. Therefore the CEMYDD molecules were arranged as polar domains with a size of several hundred nm. The crystallographic orientation of the unit cell in the film with respect to the graphite surface was found to have commensurate epitaxial coincidence. This commensurate structure was stable under STM measurements, except near the domain boundaries where the moire-like, long-range, periodic contrast modulation due to the commensurate coincidence often varied while scanning with the STM tip. Although the arrangement of molecular images themselves moved only slightly, such a collective dynamic feature at boundaries could be detected from changes in the moire-like contrast modulation.

Photophysics of novel 2,6-disubstituted benzobisthiazoles possessing chromophoric groups

A series of 2,6-disubstituted benzo[1,2-d:4,5-d′]bisthiazoles that have two photofunctional groups was synthesized, and their absorption and emission spectra in chloroform solution were examined. An anthracene derivative, 2,6-di(9-anthryl)benzo[1,2-d:4,5-d′]bisthiazole (DABBT), as well as a mono-substituted compound, 2-(9-anthryl)benzothiazole (ABT), showed a broad emission band at a long wavelength without any monomer emission of an anthryl group even for a concentration as low as 5 × 10−7 M. In contrast, naphthalene derivatives, 2,6-di(1-naphthyl)benzo[1,2-d:4,5-d′]bisthiazole (D1NBBT) and 2,6-di(2-naphthyl)benzo[1,2-d:4,5-d′]bisthiazole (D2NBBT), showed entirely monomer emission of a naphthyl group with no broad emission band at longer wavelengths. The broad emission bands observed for DABBT and ABT are attributed to an excited charge-transfer state in which an electron has transferred from a benzothiazole unit to an anthryl group.

Simulation of Long-Range Contrast Modulation in Scanning Tunneling Microscope Image of Perylene-3,4,9,10-Tetracarboxylic-Dianhydride Monolayer on Graphite

In order to simulate the scanning tunneling microscope (STM) image of perylene-3,4,9,10-tetracarboxylic-dianhydride (PTCDA) on graphite, we calculated the partial electron density, which is proportional to the tunneling current, by the extended Huckel tight binding method. The typical STM images of PTCDA have two characteristic features: (i) long-range contrast modulation caused by point-on-line coincidence and (ii) contrast difference due to molecular orientation with respect to the graphite substrate. Using the present simulation, these features can be reproduced from the expected geometrical relationship between PTCDA and graphite.

Interfacial Effects on the Spherulitic Morphology of Isotactic Polystyrene Thin Films on Liquid Substrates

The influence of interfaces on the morphology of flat spherulites of isotactic polystyrene (iPS) grown in thin films on liquid substrates was investigated. Amorphous iPS thin films spin-cast from a solution were annealed for cold crystallization on glycerol and silicone oil (nonsolvents for iPS). The number density of grown spherulites was revealed to be higher on the glycerol substrate than on the silicone oil substrate. This implies that the primary nucleation rate of crystallization is greater at the iPS/glycerol interface than at the iPS/silicone oil interface. The results may be consistent with the previous findings that concern the molecular interaction between atactic polystyrene and nonsolvents at the interface. In some cases, holes were formed in the thin films during the cold crystallization due to dewetting, which also significantly affect the spherulite morphology via, for example, transcrystallization.