Fusami Soeda

XPS study of the carbon fiber matrix interface

Abstract X-ray Photoelectron Spectroscopy (XPS) combined with gas phase chemical modification was applied to study the variation of the carbon structure and quantity of functional groups introduced by oxidation of a carbon fiber surface. The amount of functional groups effective for adhesion of the matrix at the interface was correlated to the fractional coverage of an epoxide on the fiber surface using a liquid phase chemical modification process. A mechanism for adhesion was proposed.

XPS study of oriented organic molecules: Vesicles of azobenzene-containing alkyl ammonium amphiphiles

Abstract Highly ordered molecular membranes have been playing important roles in both basic studies and applications. Among the molecules that form such molecular membranes are synthetic amphiphiles. We have observed the N 1s spectral change by aggregation of azobenzene-containing ammonium amphiphiles C12AzoCMN+Br− (M = 2, 10) in water by utilizing the freezing method. By comparing the calculated intensity ratio of azo-group nitrogen to ammonium nitrogen with that experimentally observed, the N 1s spectral change has been successfully correlated with various aggregates model structures of the amphiphiles, such as the lamella, tube, and globule. With the assumption that the N 1s photoelectron (about 850 eV in kinetic energy) mean free path is about 30 A, the bilayer lamella model has proved to be most probable for both M = 2 and M = 10 compounds. This paper has successfully demonstrated that XPS (X-ray photoelectron spectroscopy) has the potential for use in analyzing molecular orientation in addition to conventional elemental and functional group analyses.

Depth profiling of layered structures in conducting polymer thin films prepared by the potential-programmed electropolymerization method

Abstract Compositionally modulated layered structures are fabricated in polypyrrole-poly (3-methylthiophene) composite thin films by the potential-programmed electropolymerization method reported previously (T. Iyoda, H. Toyoda, M. Fujitsuka, R. Nakahara, H. Tsuchiya, K. Honda and T. Shimidzu, J. Phys. Chem., 95 (1991) 5215). The depth profilings by secondary ion mass spectrometry. Auger electron spectroscopy, transmission electron microscopy and electron probe microanalysis indicate that the resulting thin films have compositionally modulated layered structures, consistent with the designed structures. The diversified profiling by the above techniques is an extremely valuable means of analysing the layered structures of these conducting polymer thin films in terms of their periodicity and compositional modulation.

Atomic Force Microscopy of Solution Grown Polyethylene Single Crystals

Atomic force microscopy (AFM) was applied to the precise thickness measurements of thin lamellae about 10 nm thick of polyethylene single crystals which were grown from dilute solutions and precipitated on cleaved mica. The obtained values agree well with the thickness determined by small angle X-ray scattering. Moreover, AFM observation allowed determination of the thickness difference of several angstroms in the different growth sectors of small crystals about several µ m wide. From the measurements, it was concluded that the free energy of the fold surface in the 110 growth sector was 30% larger than the values in the 100 sector. The larger surface free energy in the 110 sector means higher fold energy in the growth sector.

XPS study of oriented organic molecules: The single crystal of an azobenzene-containing alkyl ammonium amphiphile

Abstract We have observed the angle-dependent XPS (X-ray photoelectron spectroscopy) N 1s spectral change of a single crystal of azobenzene-containing ammonium amphiphile C 12 AzoC 5 N + Br - . By comparing the calculated intensity ratio of the azo-group nitrogens against the ammonium nitrogen with that experimentally observed, the N 1s spectral change has successfully been correlated with the stacked bilayer model in the outermost surface of the crystal. With the assumption that the molecular axis inclines about 30 ° to the layer surface as determined by X-ray diffraction measurement, the N 1s photoelectron (about 850 eV in kinetic energy) mean-free-path was estimated to be about 24 A. The value agreed well with theoretical values. We have successfully confirmed that XPS has potentiality for analyzing molecular orientation besides conventional elemental and functional group analyses.

FT-IR-ATR observation of SiOH and SiH in the oxide layer on an Si wafer

FT-IR-ATR (Fourier transform infrared attenuated total reflectance) technique was used to measure the SiOH and SiH contents in the thermal oxide films grown on Si wafers. It was found that the SiOH groups in the bulk could be eliminated by low temperature annealing, whereas SiOH at the Si/SiO2 interface could only be removed by high temperature annealing. It was also found that gamma ray irradiation generated SiOH and SiH in the thin oxide film.

XPS study of oriented organic molecules. III: Langmuir―Blodgett membrane of a fatty acid

Abstract XPS (X-ray photoelectron spectroscopy) was used to confirm the formation of the four-layer Y-type membrane of arachidic acid prepared by the Langmuir-Blodgett method. The orientation parameter for fatty acids was defined as the ratio of the carboxylic carbon component in the C 1s spectrum. General formulae for correlating the orientation parameters with membrane model structures were derived. The advantage of XPS over the other techniques in the molecular orientation study is that XPS can determine whether a certain functional group within the molecule locates at the outermost surface or in a deep position far from the surface.

Mesoscopic layered structure in conducting polymer thin film fabricated by potential-programmed electropolymerization

Abstract Mesoscopic layered structures in conducting polymer thin films are fabricated by the potential-programmed electropolymerization method. High lateral quality in the layered structure is realized by the improvement of polymerization conditions, i.e., a mixture of pyrrole and bithiophene as monomers, a silicon single-crystal wafer as a working electrode and propylene carbonate as a solvent. SIMS depth profiling of the resulting layered films indicates a significant linear correlation between the electric charge passed and the thickness of the individual layers on a 100 A scale.

Molecular-Scale Structures of Langmuir-Blodgett Films of Fatty Acids Observed by Atomic Force Microscopy

Langmuir-Blodgett films of arachidic acid, barium arachidate, and a mixture of arachidic and behenic acids on a chemically flattened silicon substrate were observed by atomic force microscopy. The films were found to contact tightly with the substrate with a molecular slip at its steps. Lattice expansion due to barium ions was found on the barium arachidate film but not on the pure acid film. In addition, the 2×2 superlattice was found on the barium arachidate film. The superlattice structure may be caused by the formation of a hydrogen salt. Although no phase separation was found on the film made of a 9:1 mixture of the acids, the image of the expected molecular mixture has not been obtained so far.