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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.

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.

Structural Analysis of Langmuir-Blodgett Films of Alkylated Tetracyanoquinodimethanes

Structural characterization of alkylated tetracyanoquinodimethane (TCNQ) Langmuir and Langmuir-Blodgett (LB) films has been carried out. Scanning electron microscope (SEM) and atomic force microscope (AFM) observations reveal numerous platelet microcrystal domains in the alkylated TCNQ Langmuir films transferred onto a quartz substrate. The analysis of height distribution in the AFM data proves that these domains have periodic layered structure. The thickness of these layered structures agrees well with the d-values obtained by X-ray diffraction analysis of the alkylated TCNQ LB films. Moreover, the high-resolution AFM image and the d-value of the 2-dodecyl-TCNQ Langmuir film suggest that the structure of the second and the upper layers in the domains is identical to that of the single crystal. SEM and AFM measurements prove that the LB films consist of numerous platelet microcrystal domains which are superposed upon each other, resembling a mosaic structure. Therefore, the periodic structures observed in X-ray diffraction measurements of the alkylated TCNQ LB films are ascribed to the layered structure in these domains, although they are usually explained as well-defined multilayered structure.

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

Evaluation of a speech translation system for travel conversation installed in PDA

For mobile use, we are developing a multilingual example-sentence-driven speech translation system that has a multi-modal input interface to retrieve the sentence. In addition to the basic speech input mode, we apply an associative keyword mode with a software keyboard and an associative domain selection mode. The paper discusses the characteristics of each input mode, the synergistic effect obtained by combining the modes and the results of evaluations that show the difference between system performance in the laboratory and in the real world. As the evaluation criteria, we adopted the retrieval time and the retrieval precision of the sentence. When all of the modes were available, the precision within 30 seconds was 86.8% for a closed test set and 76.8% for an open-test set. When the retrieval was completed with only one operation, the average time was 10.3 seconds for a closed set. The precision was 12.0% higher than the maximum precision obtained when only one of the modes was available. The results show that synergetic effect of the combined modes certainly exists and all the modes are necessary to improve the systems usability.