Toshiyuki Aida

Fluctuation-Free Electron Emission from Non-Formed Metal-Insulator-Metal (MIM) Cathodes Fabricated by Low Current Anodic Oxidation

Fluctuation-free electron emission is obtained from MIM (Al-Al2O3-Au) cathodes. The Al2O3 layer is fabricated by anodic oxidation with a reduced electrolysis current density, i.e., a reduced oxidation rate. The slow oxidation process improves the insulating effect of the Al2O3 layer, and enables the MIM cathodes to operate in the non-formed state. The fluctuation-free emission is reproducible when the diode voltage is cut off instantaneously. With a thin Al2O3 layer, the diode voltage reguired for the cathode operation is reduced to values slightly above the work function of the top electrode.

Thin Film Growth of YBa2Cu3O7-x by ECR Oxygen Plasma Assisted Reactive Evaporation

A new apparatus equipped with an ECR oxygen plasma source, a co-evaporation system of Y, Ba and Cu and a differential pumping system was developed. YBa2Cu3O7-x superconducting films were obtained at a substrate temperature of 450–500°C. The critical temperatures of films deposited on SrTiO3, MgO and Si substrates were 87 K, 80 K and 63 K, respectively. These properties were closely related to the crystallinity of the film.

Preparation of YBa2Cu3O7-x Superconducting Thin Films by RF-Magnetron Sputtering

Thin films of Y-Ba-Cu-O system have been prepared by rf-magnetron sputtering technique. The sputtered film was a multilayer composed of (Ba, Cu, O) and (Y, Cu, O). The films were crystallized by a high temperature chemical reaction between BaCuO2 and Y2Cu2O5 layers. Critical temperatures of YBa2Cu3O7-x thin fims in this study were 80-85 K.

Power-law dissipative behavior in high-Tc superconductor

Abstract Induced voltage V in the mixed state of high- T c superconductor ErBa 2 Cu 3 O 7-x film is measured as a function of transport current I and applied magnetic field H at 77K. Both I–V characteristics and magnetoresistance exhibit similar power-law behaviors with nonuniversal exponents in the forms of V ∞ I n ( H ) and V ∞ ( H - H 0 ) m ( I ) , respectively. Response voltages to the modulated magnetic field have anomalous field-dependences nearby H = H 0 which corresponds to the lower critical field. This power-law behavior suggests that there exists a new nonlinear dissipative phase probably due to fluxiod motion.

Contact between High-Tc Superconductor and Semiconducting Niobium-Doped SrTiO3

The contact between a high-Tc superconductor of Er-Ba-Cu-O and a semiconductor of niobium-doped SrTiO3 has been examined by current-voltage measurements. The rectifying characteristic has been observed at 277 K for a sample with niobium-0.05wt%-doped SrTiO3. The breakdown voltage decreases with decreasing temperature or increasing niobium impurity concentration, and the temperature dependence of the breakdown voltage becomes more gradual with increasing niobium impurity concentration.

Light Detection by Superconducting Weak Link Fabricated with High-Critical-Temperature Oxide-Superconductor Film

The light-induced changes in the current-voltage characteristics are studied for a superconducting weak link fabricated with a polycrystalline YBa2Cu3O7-δ film. The maximum superconducting current decreases by exposure to light at temperatures up to 77 K. The sensitivity of the light detection is enhanced by the use of a photoconductive semiconductor film on the surface of the weak link.

Some fundamental properties of Sc2O3 mixed matrix impregnated cathodes

Abstract Some fundamental properties of Sc 2 O 3 mixed matrix impregnated cathodes are studied by means of electron emission measurements and surface analysis is performed by Auger electron spectroscopy. The powders of W and Sc 2 O 3 are mixed and sintered in vacuum to form a porous body in which Ba-Ca aluminate (4BaO·CaO·Al 2 O 3 0 is impregnated. The saturation current density is 10 A/cm 2 at 850–900°C (brightness temperature) for 1–13 wt% Sc 2 O 3 mixed matrix cathodes. This high current density is due to low work function patches distributed over the cathode surface, which is composed of Ba, Sc and O in a certain ratio.

Study of metal film coating on Sc2O3 mixed matrix impregnated cathodes

Abstract Electron emission and surface properties of the Sc 2 O 3 mixed matrix impregnated cathode coated with Ir, Os, Pt and Mo are studied. The cathode is composed of porous body of a metal matrix (5 wt% Sc 2 O 3 in W) and an impregnant of 4BaO·CaO·Al 2 3 , on which metal films of about 500 nm are evaporated. Sc atoms do not appear on the film surface even after prolonged heating at 1150°C, and the coated cathodes do not show the emission anomaly usually seen for Sc 2 O 3 mixed matrix cathodes. The Mo film, however, alloys easily with W in a short heat treatment time and the Sc atoms are distributed nonuniformly over the surface. The Mo coated cathode does show the emission anomaly. A simple coating with Sc film on the ordinary W matrix cathode reveals neither the surface properties nor the emission properties of Sc 2 O 3 mixed matrix cathodes.

Emission life and surface analysis of barium-impregnated thermionic cathodes

Emission life of small Ba‐impregnated thermionic cathodes suitable for use in TV tubes is investigated systematically. Cathodes are covered with an Os layer to enhance the emissivity. They have an unusual emission life in that the emission current decreases gradually with time and then drops abruptly. The early gradual decrease in emission at high cathode temperatures is caused by the phase change of the Os layer to OsW2. A linear relationship is found to exist between the logarithm of the lifetime and the reciprocal of the cathode temperature. This life end is believed to happen after the end of the reduction reaction between BaO and the porous W body and after ceasing replenishment of the low work function Ba+‐O− monolayer on the metal surface. A formula for the emission lifetime is derived from the assumption that the rate determining step is the Ba diffusion inside the pellet. Emission lifetime τ is shown to be given by τ=Ad2 exp(E/kT), where A is a constant, d is the pellet thickness, and E is the ac...

DC Gas-Discharge Display Panel with LaB6 Thin-Film Cathode

A dc gas-discharge display panel with LaB6 thin-film cathodes is proposed for data information systems. A thin-film, having a crystallographic orientation of [100], was formed on a Ni thick-film using the electron-beam evaporation technique. The low work function of the crystallographic orientation provided a low operating voltage. The normal cathode fall potential for the thin-film cathode in a Ne+Ar (0.4%) gas discharge was approximately 80 V, about 1/2 that of the commonly used Ni thick-film cathode. The display panel consisted of two glass plates: cathodes were formed on one plate (substrate) and anodes on the other. The cathodes and anodes were perpendicular to each other, and were separated by barriers formed in parallel between the anodes. Low voltage, high luminance, high luminous efficiency and stable operation were attained without the use of Hg.