Atsushi Fukuda

Perfume and flavour identification by odour-sensing system using quartz-resonator sensor array and neural-network pattern recognition

Abstract Perfume and flavour identification by an odour-sensing system using a quartz-resonator sensor array and neural-network pattern recognition has been performed. Good separations among the samples are obtained. Furthermore, orange flavours with a small amount of foreign substances have been examined. When the ratio of the foreign substances to orange flavour is more than 0.5%, the sample could be separated from an ordinary orange sample by the present system, with a detection limit near those of normal people.

SPATIAL DISTRIBUTION OF CHARGES IN ULTRATHIN POLYIMIDE LANGMUIR–BLODGETT FILMS

The spatial distribution of charges in ultrathin polyimide (PI) Langmuir–Blodgett (LB) films, with a monolayer thickness of 0.4 nm, deposited onto metals was determined by measuring the surface potential of the PI LB films as a function of the number of deposited layers. The depth of penetration of the excess charges displaced from metal electrodes into the PI LB films was about 3 nm. The saturated surface potential was an accurately linear function of the work function of the metal. We concluded that excess charges (mainly electrons) were transferred from metals into as‐deposited PI LB films until thermodynamic equilibrium was established at the metal/PI interface by electron tunneling.

Improvement of identification capability in an odor-sensing system

Abstract Recognition of the output pattern from an array of gas sensors with partially overlapped specificity is valuable in odor identification. The authors have developed a method using a quartz-resonator sensor array and neural-network pattern recognition, with which the fine differences among whisky aromas can be discriminated. In the present study, the measurement system has been improved by modifying the sample flow system and including a few lipid materials in the sensing membrane set. The identification capability has now been raised from 76% in the previous report to a recognition probability of 94%.

Perfume and flavor identification by odor sensing system using quartz-resonator sensor array and neural-network pattern recognition

A quartz-resonator sensor array and neural-network pattern recognition system previously used for whisky-aroma identification has been applied to perfume and flavor identification. Perfume and flavor identification by this odor sensing system was successfully performed although sensing membranes tuned up for whisky-aroma identification were used. Good separation among the samples was obtained.<<ETX>>

Surface Potential of Heat-Treated PI Langmuir-Blodgett Films Deposited on Metal Electrodes

The surface potential of polyimide (PI) Langmuir-Blodgett (LB) films deposited on base-Au or -Cr electrodes was measured in a box shielded from light while nitrogen gas flowed through the box. Potential differences across PI LB films before and after heat treatment (at 100°C) were measured as a function of the number of deposited layers. The surface potential observed after the heat treatment was independent of the time elapsed. It was found that the surface potentials obtained after heat treatment depend on the base-electrode materials and the number of deposited layers, possibly due to the displacement of electrons from base-Au and -Cr electrodes into as-deposited PI multilayers. Finally, we concluded that photogenerated carriers in PI LB films were conveyed along the electric field established by the electrons displaced into as-deposited PI LB films from base-Au or Cr electrodes.

Surface potential of heat-treated polyimide Langmuir-Blodgett films

Abstract The surface potential of heat-treated polymide (PI) Langmuir-Blodgett (LB) films deposited on various metalelectrodes was measured in a box shielded from light while nitrogen gas flowed through the box. The surface potential depended on base electrode material and the number of deposited layers. The surface potential saturated when the number of deposited PI LB layers was about 10. The saturated surface potential was a linear function of the work function of the metal. It was suggested that excess charges (electrons) were transferred from metal electrodes to heat-treated PI LB films until thermodynamic equilibrium was established at the metal-PI interface. The penetration depth of excess charges displaced from the metal electrodes into PI LB films was estimated to be about 4nm. In order to clarify further the formation of a space charge layer in PI LB films at the metal-PI interface, the photoinduced surface potential in heat-treated PI was also measured. It was found that the surface potential changes as a result of the displacement of photogenerated carriers along the electric field produced by excess charges.

Photoinduced Surface Potential in Polyimide Langmuir-Blodgett Films

We examined the photoresponse of the surface potential across polyimide (PI) Langmuir-Blodgett (LB) films deposited on base-Au electrodes, and then analyzed the surface potential change initiated with photoirradiation by assuming a model based on the three-step process of photoconductivity in polymers. In the model, photogeneration of carriers is of the Onsager type, where a space charge field formed at the PI/base-Au electrode interface makes a significant contribution to the photogeneration, and the succeeding carrier transport does not suffer from bimolecular recombination.

Surface Potential of Polyimide Langmuir-Blodgett Films Deposited on Metal Electrodes

The surface potential of multilayers of polyimide (PI) deposited on base-Au, Cr and Al electrodes was measured by the conventional surface potential technique. A comparison was made between the surface potential of clean base electrodes and that of base electrodes onto which various numbers of layers were deposited. The surface potential of PI depends strongly on the material of the base electrodes. It was suggested that the surface potential of PI multilayers originates from charges displaced from base electrodes to the PI multilayers.

Photoinduced Displacement Current in Polyimide Langmuir-Blodgett Films Deposited on Au Electrodes

The photoinduced displacement current across polyimide (PI) Langmuir-Blodgett (LB) films incorporated in Au/PI/air-gap/Au structures was investigated without the application of an external electric field. Transient displacement current was found to be produced by photoirradiation with a wavelength of 400 nm, because carriers were generated in PI LB films and were then conveyed along the electric field established in a Schottky depletion region in the PI LB films.

Charge Storage Phenomena and I-V Characteristics Observed in Ultrathin Polyimide Langmuir-Blodgett Films

We fabricated Au/PI/Al junctions and then examined the charge storage phenomena in polyimide (PI) layers. We also examined the current-voltage (I-V) characteristics of the junctions in connection with charge storage phenomena. It was found that numerous excess charges were injected into PI multilayers from electrodes by the application of biasing voltages. Therefore, the space charge field formed in as-deposited PI layers was distorted by the excess charges injected. It was also found that asymmetric I-V characteristics observed for Au/PI/Al junctions depended on the biasing voltages, because the space charge field formed in PI layers influenced the I-V characteristics.