Faculty Profiles - SAITO, Nagahiro

Papers - SAITO, Nagahiro

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Microarc plasma treatment of titanium and aluminum surfaces in electrolytes

Anita V., Saito N., Takai O.

Thin Solid Films Vol. 506-507 page： 364 - 368 2006.5

Language：English Publishing type：Research paper (scientific journal) Publisher：Thin Solid Films

The advanced plasma process of microarc treatment in electrolytes was utilized to prepare oxide layers on aluminum and titanium substrates by anodic conversion. This paper reports results on morphology, structure, growth rates, hardness and water contact angle measurements of titanium and aluminum oxidized surfaces obtained by microarc discharge in ecologically clean and safe electrolytes. Porous oxide layers were formed on the sample surface after the microarc treatment. The morphology of surfaces was dependent on the current intensity during the treatment. The pore diameter in the films decreased with the increase in current intensity and the thickness of the oxide film increased almost linearly with the time of treatment for a constant input power. © 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.tsf.2005.08.083

Visualization of human plasma fibrinogen adsorbed on highly oriented pyrolytic graphite by scanning probe microscopy

Ohta R., Saito N., Ishizaki T., Takai O.

Surface Science Vol. 600 ( 8 ) page： 1674 - 1678 2006.4

Language：English Publishing type：Research paper (scientific journal) Publisher：Surface Science

Human plasma fibrinogen (HPF) was observed by atomic force microscopy (AFM) and Kelvin probe force microscopy (KPFM) conducted in non-contact mode. The HPF was adsorbed on a highly oriented pyrolytic graphite (HOPG) substrate as single molecules, as aggregated bundles, and as aggregated fibers. Topographic and phase images confirmed structural changes in the HPF after exposure to air, while topographic and KPFM images confirmed fibers with the width of a single HPF molecule. Additionally, KPFM confirmed the surface potential difference between the HPF and the HOPG, and periodical potential drop reflecting the E and D domains in the fiber. © 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.susc.2005.12.058

Carbohydrate Microarrays by Click Chemistry

H. Sato, Y. Miura, T. Yamauchi, N. Saito, K. Kobayashi, O. Takai

Trans. Mater. Research. Soc. J. Vol. 31 page： 659-703 2006

Micropatterned saccharide display on the silicon surface

Sato H., Miura Y., Saito N., Kobayashi K., Takai O.

Polymer Preprints, Japan Vol. 54 ( 1 ) 2005.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Polymer Preprints, Japan

The immobilization and the micro-patterning of biomolecules on the solid surfaces are paid much attention for the application of biomaterials, and biosensors. Micro-patterned carbohydrates on solid surfaces are useful to analyze carbohydrate-protein interactions and to fabricate the scaffolds of cell cultivation. We have proposed a new method for micro-patterned carbohydrate display. The micropattern composed of hydrophobic and electrostatically positive regions were fabricated by methyl and amino terminated self-assembled monolayers (SAM). The patterned substrates were incubated in two types of aqueous solutions of PVLA and Heparin, in this order. The PVLA and Heparin site-selectively adsorbed on methyl and amino terminated SAMs, respectively. It indicated that the two dimensional matrix of PVLA and Heparin can be fabricated on the micro-patterned substrate. The micropatterning of two different components on one substrate enables two different biomacromolecules to be self-assembled into micro pattern.

Photolithographic patterning of dendrimer monolayers and pattern-selective adsorption of linear macromolecules

Yamazaki T., Imae T., Sugimura H., Saito N., Hayashi K., Takai O.

Journal of Nanoscience and Nanotechnology Vol. 5 ( 11 ) page： 1792 - 1800 2005.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Nanoscience and Nanotechnology

Alkyl groups of n-octadecyltrimethoxysilane (ODS) in a self-assembled monolayer on a silicon substrate were oxidized to carboxyl groups by partial irradiation of vacuum ultra-violet light under the photomask, producing a COOH/ODS line pattern. After active esterification of carboxyl groups, two kinds of amine-terminated dendrimers, poly(propyleneimine) and poly(amido amine) (PAMAM) dendrimers, were immobilized on a COOH line through amide-bond so that photolithographic dendrimer/ODS pattern was finally fabricated. Preparation was certified by atomic force microscopy (AFM) and surface-enhanced infrared absorption spectroscopy at transmission mode. Adsorption of linear macromolecutes was examined on PAMAM dendrimer/ODS pattern. After adsorption of poly-L-glutamic acid (PGA) at a pH below α-helix-random coil transition, rod-shape texture was observed only on the dendrimer line in an AFM image. This texture is an aggregate of α-helical PGA. Sodium hyaluronate and DNA were also adsorbed selectively on the dendrimer line, keeping the line profile, although characteristic textures were not observed. Copyright © 2005 American Scientific Publishers All rights reserved.

DOI： 10.1166/jnn.2005.434

Properties of DLC thin films produced by RF PE-CVD from pyrrole monomer

Takai O., Anita V., Saito N.

Surface and Coatings Technology Vol. 200 ( 1-4 SPEC. ISS. ) page： 1106 - 1109 2005.10

Language：English Publishing type：Research paper (scientific journal) Publisher：Surface and Coatings Technology

This paper reports the properties of diamond like carbon (DLC) thin films obtained in a capacitively coupled, RF powered, plasma enhanced chemical vapor deposition (PE-CVD) system. A precursor used was pyrrole, one of the most known monomers for conductive polypyrrole polymer processing. The deposition rate of thin films was high: 74 nm/min at 50 W and 425 nm/min at 400 W input power. The hardness and elastic modulus of thin films reached the highest values of 16.5 and 148 GPa at 400 W and the surface morphology of the films did not suffer important changes in the interval of utilized input powers: RMS roughness decreased from 0.45 nm at 50 W to 0.20 nm at 400 W. All deposited films were transparent in the infrared range. Raman measurements revealed that the increase of the input power led to a decrease of the sp3 and an increase of sp2 bonded carbon atoms in thin films. The resistivity of DLC thin films was very high for low values of RF input power (ρ> 107 kΩ cm) and decreased at higher values of input power (ρ≈ 55 kΩ cm at 400 W). By using nitrogen as a doping element the resistivity decreased to ρ ≈ 3.5 kΩ cm at 400 W and 20 sccm N2. © 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.surfcoat.2005.02.024

Surface-potential reversibility of an amino-terminated self-assembled monolayer based on nanoprobe chemistry

Saito N., Lee S., Takahiro I., Hieda J., Sugimura H., Takai O.

Journal of Physical Chemistry B Vol. 109 ( 23 ) page： 11602 - 11605 2005.6

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Physical Chemistry B

Nanoprobe chemistry offers a promising approach for the construction of nanostructures consisting of organic molecules by employing the tip of a scanning probe microscope. In a previous report, we demonstrated that a nitroso-terminated surface on an organosilane self-assembled monolayer could be converted into an amino-terminated surface by applying such a nanoprobe electrochemical technique. This paper reports on surface-potential reversibility originating from a reversible chemical reaction between amino and nitroso groups. In addition, we demonstrate surface-potential memory based on this chemical reversibility. Ammo-terminated SAMs were prepared from p-aminophenyl-trimethoxysilane through chemical vapor deposition. Surface potentials were acquired by Kelvin force microscopy. When scanning probe lithography was conducted with a gold tip at positive-bias voltages, the surface potential of the scanned area shifted dramatically in the negative direction. Scanning with negative-bias voltages led to positive shift in the surface potential of the scanned area. The surface potential could be recovered even after multiple scannings with positive and negative applied bias voltages. On the basis of this discovery, we also succeeded in demonstrating surface-potential memory via our nanoprobe electrochemical technique. © 2005 American Chemical Society.

DOI： 10.1021/jp044943k

An investigation into the effect of ionic species on the formation of ZnTe from a citric acid electrolyte

Ishizaki T., Saito N., Takai O., Asakura S., Goto K., Fuwa A.

Electrochimica Acta Vol. 50 ( 16-17 ) page： 3509 - 3516 2005.5

Language：English Publishing type：Research paper (scientific journal) Publisher：Electrochimica Acta

Cathodic electrodeposition of ZnTe film was carried out on Au/Cu substrate using three kinds of citric acid electrolytes, each with a different counter anion, i.e., sulfate, chloride, or nitrate ions, to investigate the anion species' influence on the morphology, composition and structure of the resulting electrodeposited ZnTe films. Both chloride and nitrate electrolytes gave crystalline ZnTe films with almost stoichiometric ZnTe composition under electrolytic conditions similar to those optimized previously for sulfate electrolyte. The mean crystallite size of the electrodeposited ZnTe films ranged from 13 to 37 nm. The effect of the ionic species on the crystallite size was also investigated. The degree of ZnTe(1 1 1) plane orientation of the films obtained from nitrate electrolyte was stronger than that of the films from sulfate or chloride electrolytes. High resolution SEM observations revealed different morphologies depending on the anion in the electrolytic solution. © 2005 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.electacta.2004.12.028

Fabrication of ferroelectric self-assembled fluorinated polyether monolayer on hydrogen-terminated Si(111) surface

Okano T., Inari H., Ishizaki T., Saito N., Sakamoto W., Takai O.

Chemistry Letters Vol. 34 ( 4 ) page： 600 - 601 2005.4

Language：English Publishing type：Research paper (scientific journal) Publisher：Chemistry Letters

Covalently bonded ferroelectric self-assembled monolayers on silicon surface were fabricated via hydrosilylation of terminally allylated and propargylated fluorine-containing polyether adsorbates on hydrogen-terminated Si(111) substrates. Incomplete polarization - electric field loops indicating ferroelectric property were observed in a range of bias voltage ±300 mV. Copyright © 2005 The Chemical Society of Japan.

DOI： 10.1246/cl.2005.600

High-resolution submicron patterning of self-assembled monolayers using a molecular fluorine laser at 157 nm

Nae F.A., Saito N., Hozumi A., Takai O.

Langmuir Vol. 21 ( 4 ) page： 1398 - 1402 2005.2

Language：English Publishing type：Research paper (scientific journal) Publisher：Langmuir

Using a molecular fluorine laser at 157 nm wavelength, submicron patterning of organosilane self-assembled monolayers (SAMs) is demonstrated utilizing mask-contact photolithography. An organosilane, namely, octadecyltrimethoxysilane [ODS, CH3(CH2) 17Si(OCH3)3], SAM is chemisorbed onto Si substrates covered with a 2 nm thick oxide layer and subsequently patterned using the laser. The optical path of the laser beam and the photomask-sample space are evacuated and then backfilled and purged with nitrogen during laser firing. The resulting pattern is investigated using various measurement techniques. The scanning probe microscopy images show that patterns are transferred to the SAM-covered Si substrates and that 500 nm features are successfully photoprinted in this way.

DOI： 10.1021/la0480944

Fabrication of a built-in patterned metal microstructure on a polymer substrate using a microstructured organic monolayer template

Saito N., Hieda J., Takai O.

Electrochemical and Solid-State Letters Vol. 7 ( 12 ) 2004.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Electrochemical and Solid-State Letters

We have successfully developed a novel route based on nanoimprinting lithography. In developing our approach, we demonstrated that metal on an organic monolayer could be easily transferred to a polymer surface by nanoimprinting lithography, and that patterned metal fabricated in this manner would bind strongly to the polymer substrates. © 2004 The Electrochemical Society. All rights reserved.

DOI： 10.1149/1.1819870

Effect of N doping on properties of diamond-like carbon thin films produced by RF capacitively coupled chemical vapor deposition from different precursors

Anita V., Butuda T., Maeda T., Takizawa K., Saito N., Takai O.

Diamond and Related Materials Vol. 13 ( 11-12 ) page： 1993 - 1996 2004.11

Language：English Publishing type：Research paper (scientific journal) Publisher：Diamond and Related Materials

In this paper, we report results concerning properties of diamond-like carbon (DLC) thin films obtained in different experimental conditions: various RF power values, and different precursors (methane, acetone and toluene or in combination with nitrogen). The deposition rate of DLC thin films obtained from precursors with low ionizing energy and high number of carbon atoms in molecule as acetone and toluene was higher (142 nm/min for acetone and 607 nm/min for toluene as compared with 79 nm/min for methane at 400 W input power). The highest value of hardness was obtained from methane (18 GPa). In the case of acetone and toluene precursors, the hardness increased with input power to the highest values of 16.8 and 14.8 GPa. By utilizing nitrogen as doping element, the resistivity of DLC thin films obtained from methane and acetone decreased from values higher than 107 Ω cm to lower values of 12.5 × 103 Ω cm for 3.79% nitrogen atomic concentration in the case of films obtained from methane and 40 × 103 Ω cm for 4.26% nitrogen atomic concentration in the case of films obtained from acetone. © 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.diamond.2004.05.002

Reversible nanochemical conversion

Sugimura H., Lee S., Saito N., Takai O.

Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures Vol. 22 ( 6 ) 2004.11

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures

Local chemical conversion of an organic surface that consists of a surface-confined monolayer is demonstrated in a reversible manner based on electrochemical reactions induced beneath a conductive probe tip of an atomic force microscope. The monolayer was prepared by a self-assembling technique from the precursor, p-aminophenyltrimethoxysilane. The chemical state of this self-assembled monolayer was regulated by probe-tip scanning with a bias voltage applied between the tip and substrate. With a positive substrate bias scanning, the monolayer surface was oxidized to be nitroso-terminated. With a negative bias scanning, this monolayer could be amino-terminated. These oxidation and reduction processes could be reversibly repeated. © 2004 American Vacuum Society.

DOI： 10.1116/1.1825020

Contribution of primary chemical bonding states of amorphous carbon nitride to hardness

Saito N., Ohta R., Lee K.H., Kobayashi Y., Okazaki S., Inoue Y., Sugimura H., Takai O.

Electrochemical and Solid-State Letters Vol. 7 ( 8 ) 2004.9

Language：English Publishing type：Research paper (scientific journal) Publisher：Electrochemical and Solid-State Letters

The hardness of amorphous carbon nitride (CN) was investigated by solid-state nuclear magnetic resonance (NMR) spectroscopy and Fourier transform infrared spectroscopy (FTIR). The results of NMR measurements showed that sp2 and/or sp hybrid orbitals controlled the hardness of amorphous-CN films, which had been determined by nanoindentation tests. The intensity of the C-H and CN stretching modes observed in the FTIR spectra was the weakest in the hardest sample. The decreases of -CH3 and -CH2 groups indicated that the amorphous network had increased. The sp2 hybrid orbital forms a cross-linker which plays an important role in improving of the hardness of the film. © 2004 The Electrochemical Society. All rights reserved.

DOI： 10.1149/1.1763791

Organosilane self-assembled monolayers directly linked to the diamond surfaces

Ohta R., Saito N., Inoue Y., Sugimura H., Takai O.

Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films Vol. 22 ( 5 ) page： 2005 - 2009 2004.9

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films

The organosilane self-assembled monolayers (SAM) which were linked to diamond surfaces were investigated. It was observed that the SAM were prepared from p-aminophenyltrimethoxysilane (H2N(CH)6Si(OCH 3)3, APhS) on diamond substrates and were irradiated by vacuum ultraviolet (VUV) light. It was also observed that the thickness of the SiOx layer was increased by the APhS-SAM formations and VUV irradiations. It was found that the APhS-SAM/ nano-scale SiOx/ diamond could be used for diamond-bio hybridized devices.

DOI： 10.1116/1.1776184

Fabrication of piezoelectric self-assembled fluorinated polyether monolayer on hydrogen-terminated Si(111) surface.

Okano, T; Inari, H; Saito, N; Takai, O

ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY Vol. 228 page： U471 - U471 2004.8

Photochemical reaction of organosilane self-assembled monolayer as studied by scanning probe microscopy

Sugimura H., Saito N., Ishida Y., Ikeda I., Hayashi K., Takai O.

Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films Vol. 22 ( 4 ) page： 1428 - 1432 2004.7

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films

The study of a patterning process of an alkylsilane self-assembled monolayer (SAM) using vacuum ultraviolet (VUV) light at 172 nm, by charaterizing the VUV-irradiated SAM surfaces through lateral force microscopy (LFM) and Kelvin force microscopy (KFM), was presented. The relative frictional forces and surface potentials of the VUV-irradiated regions at various irradiation dose rates were measured by LFM and KFM. VUV-irrated SAMs showed particularly lower surface potentials than the other SAM surface potentials than the other SAM surfaces with different dose rates, at a certain dose rate of 10-15 J/cm 2. It was observed that LFM and KFM measurements were promising in order to probe chemistries on organic thin films proceeding.

DOI： 10.1116/1.1764818

Exploration of the chemical bonding forms of alkoxy-type organic monolayers directly attached to silicon

Saito N., Lee S., Maeda N., Ohta R., Sugimura H., Takai O.

Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films Vol. 22 ( 4 ) page： 1425 - 1427 2004.7

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films

The preparation of alkoxy-type organic monolayers on hydrogen-terminated silicon from 1-undecanol (UN), 1-nonanol (NO), 1-heptanol (HP) and 4-phenylphenenol (PP) was discussed. The characterization of these monolayers was based on X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR). A SiOx peak was clearly observed for the HP, NO and PP monolayers. It was shown that the generation of SiO x in the PP monolayer was due to steric hindrance of the aromatic rings. It was found that the the -CH2-region in the FT-IR spectra showed that the shorter alkyl chains promoted the formation of gauche conformers in the monolayers.

DOI： 10.1116/1.1759353

Generation of amino-terminated surfaces by chemical lithography using atomic force microscopy

Saito, N; Maeda, N; Sugimura, H; Takai, O

LANGMUIR Vol. 20 ( 13 ) page： 5182 - 5184 2004.6

Language：English Publishing type：Research paper (scientific journal) Publisher：Langmuir

Self-assembled monolayers (SAMs) covered with nitroso end groups were reduced using an atomic force microscope. As the bias voltage become more negative (beyond -4 V), the surface potential of the scanned area become closer to that of the amino-terminated SAM. Following this chemical change, however, no change in topographic features was detected, implying retained stability of the underlying SAM layer. We then released carboxylate-modified polystyrene (PS) spheres into a pH 4 solution containing the sample. Subsequent imaging with atomic force microscopy (AFM) revealed that these PS spheres were only selectively immobilized on the regions that were originally scanned at -6 V to form amino termination. In summary, using AFM set to a specific voltage, we were able to selectively generate micropatterned regions of the SAM with amino termination.

DOI： 10.1021/la0353428

UV Raman spectroscopic probing into nitrogen-doped hydrogenated amorphous carbon

Ohta R., Saito N., Okazaki S., Inoue Y., Sugimura H., Takai O.

Thin Solid Films Vol. 457 ( 1 ) page： 128 - 132 2004.6

Language：English Publishing type：Research paper (scientific journal) Publisher：Thin Solid Films

From the viewpoint of hardness, chemical bonding states of nitrogen-doped hydrogenated amorphous carbon film were characterized by Ultra violet (UV) Raman spectroscopy and Fourier transform infrared (FT-IR) spectroscopy. UV Raman spectra revealed that disorder of the structure in nitrogen-doped hydrogenated amorphous carbon was promoted by applying higher bias voltages in the preparation. FT-IR spectra showed that N-H bonds decreased and sp 3C-sp3N bonds increased with the increase of the bias voltages. The content of sp3C-sp3N bonds was maximized at the bias voltage of -800 V. We found out a guarantee that the content of sp 3C-sp3N bonds against bias voltages correlated with the hardness obtained by nanoindentation test. The structural disorder and the increase of sp3C-sp3N bonds are possible source of the hardness in the case of nitrogen-doped hydrogenated amorphous carbon. © 2003 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.tsf.2003.12.049

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