Masamitsu Kaneko

Realization of polymeric optical integrated devices utilizing organic light-emitting diodes and photodetectors fabricated on a polymeric waveguide

Direct fabrication of organic light-emitting diodes (OLEDs) and organic photodetectors (OPDs) on polymeric substrates, i.e., polymeric waveguide substrates to form flexile optical integrated devices is demonstrated. The OELD and OPD were fabricated by organic molecular beam deposition (OMBD) technique on a polymeric or a glass substrate, for comparison. The device fabricated on a polymeric substrate shows similar device characteristics to that on a glass substrate. Optical signals of faster than 100 MHz have been created by applying pulsed voltage directly to the OLED utilizing diamine derivative, or rubrene or porphine doped in 8-hydoxyquinolinum aluminum derivatives, as an emissive layer. Electrical signals are successively converted to optical signals for optical transmission of moving picture signals with OLED fabricated on a polymeric waveguide. OPDs utilizing phthalocyanines derivatives with superlattice structure provide increased pulse response with input optical signals, and the OPD with the cutoff frequency of more than 5 MHz has been realized.

Electrolyte and strain dependences of chemomechanical deformation of polyaniline film

Abstract Chemomechanical deformation of polyaniline has been studied in a variety of aqueous acids such as HCl, HI, HBF 4 , HClO 4 , H 2 SO 4 and Benzenesulfonic acid and also as the function of strain. The samples prepared from cast film and also gel form from NMP solution are tested. The elongation ratios, i.e., the increment of elongation divided by the original length, is about 3~5% depending slightly on the acids, viz., size of anions. The lifting power of load is 2~3MPa along the stretched direction.

The electrochemical actuator using electrochemically-deposited poly-aniline film

Abstract Electrochemomechanical polymer actuators were fabricated by using the electro-deposited poly -aniline film. Using LASER displacement meter, we can easily get the in-situ observation of the displacement and the cyclic voltammogram[1]. At the redox reaction from leuco-emeraldine salt to emeraldine salt(ES), PANI film showed large deformation. On the other hand, at the redox reaction from ES to pernigraniline salt, PANI film showed the slight contraction.

Large reduction of leakage currents in AlGaN Schottky diodes by a surface control process and its mechanism

Leakage currents in AlGaN Schottky diodes were investigated systematically by using a rigorous computer simulation based on the thin surface barrier model taking account of unintentionally doped surface donors. The leakage currents in AlGaN Schottky diodes have stronger bias dependence and smaller temperature dependences as compared with those of GaN diodes. It was shown that these features were associated with shallow oxygen donors located near the AlGaN surface. Then, an attempt was made to remove oxygen and suppress leakage currents by a surface control process using an ultrathin Al layer and subsequent annealing. An in situ x-ray photoelectron spectroscopy analysis indicated the formation of Al2O3 layer during the surface control process, suggesting efficient gettering of oxygen from the surface. C-V analysis directly indicated the reduction of shallow donors by the surface control process. A remarkable reduction of reverse leakage currents of four to five orders of magnitude took place in large area ...

Electrochemomechanical deformation of polyaniline films

The deformation of unstretched and stretched polyaniline (PANI) films by the electrochemical cycle has been studied. An anisotropic deformation is observed. The largest expansion and contraction upon oxidation and reduction, respectively, are observed for the direction perpendicular to the draw axis. The deformation parallel to the draw axis is the smallest for oxidation leucoemeraldine salt to emeraldine salt (ES), and shows even slight contraction upon oxidation from ES to pernigraniline salt. The expansion ratio Δl/ l0, where Δl is the increment of expansion and l0 is the original length, is found to be proportional to the degree of oxidation. In the unstretched film, Δl/ l0 is about -2% at 20% reduction from the ES state. The results are discussed in terms of intercalation of dopant ions per repeating unit between chains and the conformational change of chains.

Mechanochemoelectrical effect of polyaniline film

Abstract The mechanically induced electrochemical current have been observed in the free standing film of conducting polymer, polyaniline (PAni). This mechanochemoelectrical effect is contrasted with the electrochemomechanical deformation. The amount of mechanically induced charge was proportional to the magnitude of the strength of load as well as the dimensional change of the film. The amount of induced charge depended upon the degree of oxidation or doping state of PAni fihn.

Response of Chemomechanical Deformation in Polyaniline Film on Variety of Anions

Dependences of chemomechanical response of polyaniline film on various acids such as aqueous HCl, H2SO4, HClO4 and HBF4 have been studied. Reversible deformation of the film upon oxidation and reduction was directly measured by a laser displacement meter. The deformation ratio of more than 3% was obtained along the stretched direction of the film in HClO4 and HBF4 solution. It is found that the magnitude and transient response of deformation closely relate to the mass of anions.

Surface Control Process of AlGaN for Suppression of Gate Leakage Currents in AlGaN/GaN Heterostructure Field Effect Transistors

We proposed a surface control process for suppressing the tunneling leakage of Schottky gates on AlGaN/GaN heterostructures. For the recovery of nitrogen-vacancy-related defects and reduction in the amount of oxygen impurities at the AlGaN surface, the process consisted of nitrogen radical treatment, the deposition of an ultrathin Al layer, UHV annealing and finally the removal of the Al layer. Ni/Au Schottky gates fabricated on processed AlGaN surfaces showed pronounced reduction in leakage current and a clear temperature dependence of I–V characteristics, indicating the effective suppression of tunneling leakage in current transport through AlGaN Schottky interfaces.

Electrochemornechanical deformation in polyaniline and poly(o-methoxyaniline)

Abstract pH dependencies of electrochemomechanical deformation (ECMD) and standard redox potential, E 1/2 in poly( o methoxyaniline) (PmAn) have been studied between the states of leucoemeraldine and emeraldine salts. It is found that the magnitude of ECMD is constant of ca. 3% at pH > 2.0 and decreases gradually below the pH 2.O. The result is explained by the redox reactions of anion doping/dedoping process and proton exchange process at pH > 2.0 and pH E 1/2 into consideration. A surprisingly large contraction ratio of more than 20% is obtained at the thickness direction of cast films in ECMD of polyaniline/HCl system. This fact is accounted by the anisotropic shrinking of cast film during the dry process.

Electrochemomechanical deformation of polyaniline films doped with self-existent and giant anions

Abstract Electrochemomechanical deformation of polyaniline films, which are substituted with sulfonic acid as a self-dopant and doped with camphor sulfonic acid as a giant dopant, have been studied. Upon oxidation, the self-doped polyaniline film basically contracts by proton doping, in contrast to the expansion by anion doping in usual polyaniline films. The film polymerized in camphor sulfonic acid by a constant-current method also shows proton dedoping and slight expansion upon oxidation. These results indicate that the chemomechanical deformation of these polyanifnes by oxidation is primarily determined by the dedoping of protons or oxonium ion, and cancelled by the expansion due to electrostatic repulsion and/or conformational change resulting from the delocalization of π electrons.