Masayoshi Masui

Gas sensitive properties of copperphthalocyanine thin films

Abstract Copperphthalocyanine (CuPc) thin films, about 250 nm thick, were prepared by vacuum evaporation on glass substrates, and their gas sensitive properties were examined. Two kinds of CuPc films, polycrystalline and amorphous, were obtained by changing the substrate temperature. A pair of Au electrodes were vacuum deposited on the CuPc films, and the conductivity change associated with introduction of NO 2 gas into the measuring chamber was measured. The conductivity increased by several orders of magnitude associated with introduction of NO 2 gas (1000 ppm) for both the specimens at room temperature. The gas sensitivity of the amorphous CuPc film was higher than that of the polycrystalline film. This result was attributed to the fact that stacking of CuPc molecules was more loose in the amorphous film than in the polycrystalline film. The gas sensitivity and the response were found to be improved with light irradiation.

Electrochromic behavior of amorphous copperphthalocyanine thin films

Amorphous and polycrystalline copperphthalocyanine thin films were prepared by vacuum evaporation, and their electrochromic behavior and voltamogramms were examined in a liquid electrolyte. Amorphous films prepared at the substrate temperature of -130°C underwent three color transitions (from blue to violet, then to green and to blue again) corresponding to the three peaks on the voltamogramms in the lithium perchlorate solution. In contrast, the polycrystalline thin films prepared at the substrate temperature of 180°C did not exhibit color change.

Effects of Anthracene Doping on Electrical and Light-Emitting Behavior of 8-Hydroxyquinoline-Aluminum-Based Electroluminescent Devices

Organic electroluminescent (EL) cells consisting of an anthracene-doped 8-hydroxyquinoline aluminum light-emitting layer and a hole transport layer were prepared by co-evaporation, and their electrical and light-emitting behavior was examined. It was confirmed that anthracene doping increased the available current density of the EL cells and EL efficiency, which caused an increase in EL brightness. However, the EL spectrum was only slightly affected by the anthracene doping.

Plasma oxidation of Cu, Ti and Ni and the photoelectrochemical properties of the oxide layers formed

Abstract Plasma oxidation of Ti, Cu and Ni was carried out using a conventional diode-type glow discharge system. Structural and photoelectrochemical properties of the oxide layers formed were examined. Electron diffraction confirmed the formation of a TiO2, Cu2O/CuO, and NiO layer on the Ti, Cu, and Ni surfaces, respectively, after the plasma oxidation. Photoelectrochemical solar cells were fabricated using the oxide layers formed as a semiconductor electrode. The TiO2 electrodes showed moderate photoresponse under anodic potentials in a methanol aqueous solution, while the Cu2O/CuO and NiO electrodes showed a weak photoresponse under cathodic potentials. In conclusion, the TiO2 layers prepared by plasma oxidation work well as a semiconductor electrode for a photoelectrochemical cell and are stable in methanol solution.

Effects of Molecular Configurations on the Electrical Resistivity of Titanylphthalocyanine Thin Films

Carrier transport in titanylphthalocyanine (TiOPc) thin films was studied. TiOPc thin films of various crystallinities were prepared by vacuum evaporation at substrate temperature varying from -160 to 20° C. The film deposited at the substrate temperature of 20° C was polycrystalline, while the films deposited at lower substrate temperatures were amorphous. The resistivity perpendicular to the film plane was lower than that parallel to the film plane for the polycrystalline TiOPc films. The difference in the resistivities between perpendicular and parallel to the film plane decreased with a decrease in the film crystallinity. A molecular configuration model for the TiOPc thin films, which explains the anisotropy of the film resistivity, has been proposed. In order to validate the model, the carrier mobility in the TiOPc thin films was determined by time-of-flight measurements.

Contact charging of a-Se electrophotographic photoreceptor with molten gallium

Contact charging of an amorphous selenium (a-Se) electrophotographic photoreceptor was studied employing molten gallium as the contact medium. Bias voltage was applied between the photoreceptor and the molten gallium, and the surface potential of the photoreceptor was monitored with a surface potentialmeter. The photoreceptor was charged to close to 100% of the bias voltage for both the positive and negative biases. The charging mechanism of the a-Se photoreceptor with molten gallium was attributed to charge injection and trapping. Uniformity of the surface potential of the photoreceptor contact-charged with molten gallium was confirmed.

Influence of naphthacene doping on the electrical and light-emitting behavior of 8-hydroxyquinoline aluminum based electroluminescent devices

Abstract Examined was the influence of naphthacene doping to the light-emitting layer of 8-hydroxyquinoline aluminum (Alq3) on electrical and light-emitting behavior of organic electroluminescent (EL) cells. The light-emitting and hole-transport layers of the EL cells were prepared by using a coevaporation method. X-ray diffraction patterns indicated an amorphous structure of the Alq3 layer regardless of the doping. Heavy doping decreased both the current density and brightness. The EL peak at around 490 nm increased with an increase in the naphthacene concentration, whereas the spectrum was not shifted by the doping. The EL peak was not due to the emission of naphthacene molecules. The light-emitting behavior of the EL cells due to the doping will be discussed.

Copper-phthalocyanine thin film photoelectrochemical cells

Abstract Copper-phthalocyanine (CuPc) thin layers were prepared by vacuum evaporation and RF sputtering, and their photoelectrochemical behavior in NaCl solution was studied. The photoelectrochemical cells with evaporated CuPc layers showed photosensitivity in the visible region, while the cell with RF-sputtered CuPc layers showed little photoresponse. The cell with evaporated CuPc layers over-coated with an RF-sputtered thin CuPc layer was fairly stable in NaCl solution. However, the energy conversion efficiency was low due to the high resistivity of the CuPc layers.

Transmission and Mechanical Characteristics of an Image Fiber under Gamma-ray Irradiation at High Temperature

In the nuclear industries, a visual inspection is required to confirm the integrity of the facilities and components. Recently, a silica-based image fiber has been used for visual inspection in the nuclear facilities. As the emphasis on visual inspection increases, an image fiber which can function in harsh environments, such as under high dose rate, narrow spaces and high temperature is required. It is thus necessary to study the transmission and mechanical characteristics of a silica-based image fiber exposed to γ-ray irradiation and elevated temperatures. We investigated the transmission loss characteristics and mechanical strength under γ-ray irradiation at high temperature with the objective of identifying the causes of deterioration of the image fiber. The induced loss of the transmission in the visible wavelength region was caused by È center and NBOHC (non-bridging oxygen hole center), and their annealing effect by thermal energy was confirmed. We believe that a high radiation resistant image fiber can be realized by improving its manufacturing condition, since it was identified that there was close relation between the induced loss of transmission and the thermal history of the glass material during melt-fused process of image fiber manufacturing. The mechanical characteristics were also investigated. The mechanical strength decreased by the deterioration of the primary coating. A secondary coating resistant to heat and radiation contributes to maintaining mechanical strength of the image fiber.

Electrochromic behavior of amorphous cobaltphthalocyanine thin films

Amorphous cobaltphthalocyanine thin films were prepared by vacuum evaporation, and their electrochromic behavior and voltammograms were examined in LiCl0 4 , KN0 3 , KCl and MgCl 2 aqueous electrolytes. The amorphous thin films prepared at the substrate temperature of -120°C, clearly exhibited electrochromism in LiCl0 4 and KN0 3 aqueous electrolytes. The specimen films underwent five color transitions (from blue to red-violet, then to blue, then to green, then to yellow-green and then to blue) corresponding to the five peaks on the voltammograms in LiCl0 4 aqueous electrolyte. The amorphous films which were evaporated in low vacuum (1.33 X 10 -1 Pa) exhibited electrochromism more clearly, compared to those evaporated in high vacuum (1.33 X 10 -4 Pa). Because the former films are low in density, it is easy for anions to be injected and extracted in the films.