Yoshiyuki Osada

Magnetic tunnel junction device with perpendicular magnetization films for high-density magnetic random access memory

We present here a magnetic tunnel junction device using perpendicular magnetization films designed for magnetic random access memory (MRAM). In order to achieve high-density MRAM, magnetic tunnel junction devices with a small area of low aspect ratio (length/width) is required. However, all MRAMs reported so far consist of in-plane magnetization films, which require an aspect ratio of 2 or more in order to reduce magnetization curling at the edge. Meanwhile, a perpendicular magnetic tunnel junction (pMTJ) can achieve an aspect ratio=1 because the low saturation magnetization does not cause magnetization curling. Magnetic-force microscope shows that stable and uniform magnetization states were observed in 0.3 μm×0.3 μm perpendicular magnetization film fabricated by focused-ion beam. In contrast, in-plane magnetization films clearly show the presence of magnetization vortices at 0.5 μm×0.5 μm, which show the impossibility of information storage. The PMTJ shows a magnetoresistive (MR) ratio larger than 50% w...

A 10‐in. surface‐conduction electron‐emitter display

A 10-in. flat-panel display (FPD) with surface-conduction electron-emitter (SCE) cathodes can be fabricated through a printing process. Ultrafine particle films of the SCEs are deposited by using ink-jet printing. A prototype achieves full-color and full-motion pictures comparable to CRTs. The feasibility of larger and low-cost SCE displays has been confirmed.

Glow discharge polycrystalline silicon thin‐film transistors

Thin‐film transistors were fabricated from polycrystalline silicon films which were produced by glow discharge decomposition of silane at 500 °C on thermal oxidized silicon substrates. The dependence of the crystalline and electrical properties was observed for thicknesses from about 500 to 4500 A. As the film grew thicker, the strongly (110) oriented polycrystalline structures became predominant. The conductivity changed from 4×10−9 to 10−6 (Ω cm)−1 and the activation energy from 0.57 to 0.5 eV. The field‐effect mobility of these thin‐film transistors also varied with the thickness of the film.

An experimental observation of photo-induced carrier multiplication in hydrogenated amorphous silicon

A photo-induced carrier multiplication in a hydrogenated amorphous silicon has been observed. A careful measurement of photo-carrier generation has been done with amorphous silicon Schottky barrier structure junctions as a function of incident photon energy in the range between 1.55eV and 6.2eV. The quantum efficiency is estimated to be multiplied by a factor of two in higher photon energy region than 5.4eV. This multiplication can be explained by an interband carrier ionization due to the energy given by a high energy photo-carrier.

Temperature dependence of glow discharge polycrystalline silicon films and thin film transistor

Abstract We observed that the conductivity of glow discharge polycrystalline silicon films changed from 10 −5 to 10 −7 (Ω · cm) −1 at substrate temperature of about 350–400°C, which was associated with the change of activation energy. At substrate temperatures lower than about 350°C, the films showed broad ring patterns with randomly oriented microcrystallites, and at higher temperatures above 400°C the preferred (110) orientation appeared. The field effect mobility of polycrystalline silicon increased as substrate temperature increased.