S. Shiokawa

Photoelectric Effects in Organic Diodes

Photovoltaic behavior of the merocyanine dye family with a rhodanine ring has been systematically studied by employing eight different derivatives in the diode structure Al/evaporated dye/Ag. Each dye film behaves like a p-type semiconductor with a rectifying barrier at Al interface and an Ohmic contact at Ag electrode. The open circuit photovoltage as high as Voc1.5 V was observed for one of the derivatives, while the fill factor remained f.f.0.25 in all cases. The chemical stability of the dye molecules during and after evaporation is also discussed on the basis of the results obtained by the thin-layer chromatography.

Study of SAW propagation characteristics by frequency‐translated holography

Under the condition of continuous acoustic generation the patterns of forward, backward, and standing SAW’s propagating on a y‐cut z‐propagating LiNbO3 crystal were observed clearly by the frequency‐translated holographic technique. The parameters of surface‐wave propagation velocity, reflectivity, and transmissivity for an interdigital transducer could be obtained by this technique.

Two Dimensional Mapping of SAW Propagation Constants by Using Fresnel-Phase-Plate Interdigital Transducer

The methods of measuring the acoustic properties of solids by using the acoustic beams from interdigital transducers (IDT) is described. An IDT can radiate acoustic waves into liquid in oblique directions with respect to the substrate surface, and the wave fronts can be arbitrarly controlled by designing the IDT shape. One IDT couple is used to measure the acoustic properties of a solid sample. In the present study, we show a new method for focusing the beam from an IDT and measuring the acoustic properties of solids. An interdigital electrode is divided into several sections, each of which is placed to form a one dimensional Fresnel phase plate (FPP) on a piezoelectric substrate. It has been found that the FPP IDT generates a converging beam onto a focal plane, and the present system is suitable for measuring the two dimensional variation of leaky SAW phase velocity on a sample surface.

Observation and study of SAW by holographic technique

A holographic technique for studying amplitude distribution of traveling, reflecting, and standing surface acoustic waves is described. The amplitude distribution can be directly displayed, and the phase velocity is accurately determined.