Akira Taomoto

Electrical Switching in Evaporated Lead Phthalocyanine Films

The switching characteristics of a sandwich cell having a Au-lead phthalocyanine-Au structure were studied. Switching was observed in a film which was evaporated at a rate of 10 A/s and consisted of a mixture of grains of monoclinic structure and amorphous fraction. The presence of moisture was necessary for switching.

Structural control of evaporated lead-phthalocyanine films

Monoclinic lead-phthalocyanine crystal film having only (320) orientation and monoclinic crystal film composed of lower (200)-and upper (320)-rich orientation were obtained at a substrate temperature of 293 K, and deposition rates higher than 1.0 nm s−1 and from 0.8 to 0.2 nm s−1, respectively. A film consisting of mixed triclinic and monoclinic crystals in which the distribution was almost homogeneous was obtained at a substrate temperature of 293 K and a deposition rate of 0.1 nm s−1, and a pure triclinic crystal film was obtained at a substrate temperature of 373 K.

Lead phthalocyanine Langmuir-Blodgett films

Abstract Different orientations of the phthalocyanine ring were obtained in Langmuir-Blodgett (LB) films of tetrasubstituted phthalocyanine lead, depending on the properties of the substituents ( t -butyl, cumylphenoxy and pentoxy groups). This difference affected their electrical properties; tetrapentoxy phthalocyanine lead LB films exhibited high conductivity (10 −4 −10 −7 S cm −1 ) in the direction parallel to the substrate, while the others had insulating properties. This high conductivity was attributed to the formation of a face-to-face stack of lead phthalocyanine molecules in the LB film.

Mixed-stack charge-transfer films prepared by Langmuir-Blodgett technique and donor doping

Abstract The formation of mixed-stack charge-transfer (CT) films was studied. Spectroscopic analysis suggested that donor doping to a 2-octadecyl-7,7,8,8-tetracyanoquinodimethane (C18TCNQ) film prepared by the Langmuir-Blodgett technique resulted in the formation of the mixed-stack CT film when 3,3′,5,5′-tetramethylbenzidine (TMB) was used as a donor, while degradation of the CT complex was observed when N,N,N′,N′-tetramethyl-p-phenylenediamine was used. Although X-ray diffraction measurements suggested that the order of the layered structure and crystallinity of the film were decreased by the doping, it was proved that the molecular columns of TMB and C18TCNQ were preferentially oriented along a substrate from polarized electronic spectra and scanning electron microscope observation. Therefore, non-linear electrical conduction as observed in mixed-stack CT crystals was expected. In the current density-electric field characteristic for the TMB-C18TCNQ film, the non-linearity was weaker than that observed in a TMB-TCNQ crystal. Furthermore, a temperature-induced neutral-ionic (N-I) phase transition was not observed from 4.2 K to room temperature in a spectroscopic measurement.

Nonlinear Electrical Properties of Evaporated Lead Phthalocyanine Films

Current-voltage characteristics of Au/evaporated lead phthalocyanine film/Au sandwich-type cells showed nonlinear electrical electrical properties with asymmetric barriers. From analyses of crystal structures of PbPc films, these barriers were found to be attributable to nonuniformity of crystal structure and orientation along the film thickness

Effect of Electrolyte Polymer Acidity on Platinum Degradation in MEAs

We fabricated MEAs having the EW200 or EW1000 electrolyte in the catalyst layer. The potential cycle test (square-wave potential cycling between 0.6-1.0 V with a pulse width of 3 s) was performed for these MEAs to evaluate the ECA change from CVs. It was revealed that the ECA decrease of the EW200 MEA was 1.6 times faster than that of the EW1000 MEA. It was revealed that the onset shift of the platinum oxidation potential, caused by the sulfonic acid group adsorption [6], depended on the electrolyte EW. The shifts were 0.7 V and 0.8 V for the EW1000 MEA and the EW200 MEA, respectively. These differences would presumably affecte on the ECA change rate.