Munehisa Mitsuya

Fluorescence spectra of vacuum-deposited films of ω-(1-pyrenyl)alkanoic acids

Abstract Vacuum-deposited films of ω-(1-pyrenyl)alkanoic acids with different chain length were prepared using a deposition rate of ≈1 nm min . Their fluorescence spectra consist of pyrene monomer fluorescence and two new emissions; no excimer-like emission was detected as a major component. These fluorescence results are considered in terms of pyrenyl aggregates characteristic of a deposited film.

Fluorescence spectral changes of vacuum-deposited films of ω-(1-pyrenyl)alkanoic acids induced by an excimer laser: molecular aspects of laser annealing

Abstract Vacuum-deposited films of ω-(1-pyrenyl) alkanoic acids showed fluorescence spectral changes upon irradiation with an excimer laser and a Xe lamp, although no absorption spectral change was detected. It was confirmed that this characteristic phenomenon depends on the number of methylenes in the chain and that a non-linear photochemical process (with respect to irradiation intensity) is involved.

Fluorescence characteristics, formation mechanism and chromophore association of ω-(1-pyrenyl) alkanoic acid films prepared by vacuum deposition

Abstract Thin films of ω-(1-pyrenyl) alkanoic acid were prepared by vacuum deposition and their fluorescence properties were studied using a picosecond single-photon counting method. Their fluorescence spectra exhibited a structured emission ascribable to a new aggregate. The deposition mechanism and the resulting chromophore association in the film were examined by varying deposition rate and chromophore content. The emission with long lifetime characteristic of a 1-substituted pyrene suggested that the compound was evaporated as a single molecule.

Ultraviolet photoelectron spectroscopy of oriented carboxylic acid films prepared by vacuum deposition

Abstract Ultraviolet photoelectron spectra were measured for films of aliphatic carboxylic acids made by vacuum deposition. Their threshold ionization potentials varied within 0.7 eV according to the measure of molecular orientation. This variation is explained by dimer formation in a highly crystalline film.

Ablative organic films for optical recording

This work presents a new type of optical recording medium for a diode laser which is three times more sensitive than a chalcogenide thin film. This medium has a tetralayer structure of n–hexatriacontane, zinc stearate, Sb2S3 and Bi. The Bi layer absorbs a recording light beam and organic layers are ablated by heat evolved in the Bi layer. The high sensitivity characteristic of this medium is attributed to the use of low‐melting‐point material as the ablating layer and the effective use of the incident beam.

Determining the distribution of silicon monofluoride on hydrofluoric acid-treated Si (111) surface by exchange reaction with molecules at the solid/liquid interface

Silicon monofluoride (Si–F) species on hydrofluoric acid (HF)-treated silicon surface have been shown to be quantitatively replaced by nucleophilic reagents at the solid/liquid interface, but some Si–F remain intact. The chemisorption of molecules with larger dimensions results in a decrease in the proportion of fluorine that is replaced. These results can be attributed to steric hindrance by the adsorbed molecules. This is explained by a model in which Si–F are grouped together to form islands of Si–F species on a predominantly H-terminated Si surface.

Study of Initial Stage of Molecular Adsorption on Si(100) by Scanning Tunneling Microscopy

We have investigated the initial stage of adsorption of a conjugated aromatic compound, 1,4-bis[β-pyridyl-(2)-vinyl]benzene (P2VB), on the clean Si(100)–2×1 surface. Using scanning tunneling microscopy (STM), we observed four different adsorption directions. An individual molecule appears as two or three bright spots, the brightness and distance between bright spots varying for different adsorption directions. We conclude that STM revealed the electronic states of the Si(100) dimers modulated by the adsorbed molecules, rather than the molecules themselves. Initial stage of adsorption of this molecule is explained by considering the molecular size and shape and strong interaction between the molecule and the Si dimers.

Construction of artificial monolayer assemblies on Si(111) surface using silicon monofluoride as a chemisorption site

Abstract Adsorption of molecules from a solution onto a fluorine-terminated Si(111) surface has been examined using X-ray photoelectron spectroscopy. The decrease in the F1s peak intensity assigned to the surface Si–F bond is accompanied by a quantitative increase in the core electron peaks ascribed to the molecule, while some Si–F remain intact. The adsorption of molecules with larger dimensions results in a decrease in the proportion of surface fluorine that is replaced. These results show that the substitution reaction proceeds until the steric hindrance of adsorbed molecules limits further adsorption. Fourier transform infrared attenuated total reflection reveals the molecule to be covalently bonded to the silicon surface giving monomolecular coverage. Dicarboxylic acids are shown to adsorb through only one of the two carboxyl groups, the other end being exposed at the monolayer–air or monolayer–liquid interface. Free carboxyl groups on the adlayer, after being converted to chloroformyl groups by chlorination reagents, act as chemisorption sites for other molecules.

Metal coating of organic thin films for thickness measurements by a stylus method

The metal coating on the surface of organic thin films has been examined to measure their surface profile by using a scanning stylus on them. The thickness of a Langmuir–Blodgett film has been successfully obtained by covering a sample with a platinum layer some nm thick. The network of the deposited overlayer is considered to be responsible for an increase in mechanical strength sufficient to endure a stylus load.

Ultraviolet photoelectron spectroscopic study of perfluorinated carboxylic acid monomolecular films prepared by vacuum deposition

Ultraviolet photoelectron spectra have been measured for monomolecular films of perfluorinated carboxylic acids prepared by vacuum deposition. Their threshold ionization potentials were determined to be 8.5 eV and their work functions larger than those for other organic compounds. The escape depth of photoelectrons through the perfluorocarbon chain was evaluated at 2.3 nm. These results are interpreted in relation to the large electronegativity of constituent fluorine atoms.