Masao Aozasa

Effects of gas impurities in the sputtering environment on the stoichiometry and crystallinity of ZnS:Mn electroluminescent-device active layers

ZnS:Mn electroluminescent (EL) device active layers were prepared using the RF magnetron sputtering method employing a powder target. The active layer was prepared under specified sputtering conditions, and in situ analysis was carried out by quadrupole mass spectroscopy (QMS) and optical emission spectroscopy (OES). The effects of gas impurities as a function of the sputtering environment on the active layer quality, and EL device characteristics were examined. Gas impurities in the sputtering environment were observed by QMS. Gases of mass numbers 18 (H2O), 28 (CO/N2), and 32 (O2) a.m.u. had unfavorable effects on the preparation of the active layer, which demonstrates the importance of reducing the concentration of these gases in the preparation of high quality active layers for EL devices. In the optical emission spectra in sputtering plasma, when the Ar (750.3 nm) peak intensity is normalized as unity, the inverse of emission intensity at 472.2 and 636.2 nm from Zn could be utilized as a quality factor of the sputtering environment.

Bias effects on the deposition of hydrogenated amorphous silicon film in a glow discharge

Bias effects on the deposition of hydrogenated amorphous silicon (a‐Si:H) film in the glow discharge were investigated by triode system which can control the negative bias without changing the other deposition conditions. The growth rate, H content, and photoconductivity of the film deposited at the substrate temperature 300–320 °C increased with the negatively enhanced bias. The results would be due to the enhancement of  ion flow by the bias and show that the bias has an advantage for the improvement of the a‐Si:H film characteristics.

CaS:Eu, F Thin Film Electroluminescent Devices Prepared by RF Sputtering with Hydrogen-Argon Mixture Gas

CaS:Eu, F electroluminescent devices with high luminous characteristics were prepared by rf-magnetron sputtering. The film quality of the active layer was improved by preparation with hydrogen-added argon sputtering gas. The active layer thus prepared has preferential (220) orientation and enhanced columnar structure with reduced incorporated fluorine atoms. The environment around the luminescent center was also affected to some extent by hydrogen addition to the argon sputtering gas. A device with the luminance of 250 cd/m2 and the luminous efficiency of 0.2 lm/W at a 1 kHz sine wave operation was prepared.

ZnS:Eu thin film electroluminescent devices prepared by r.f. magnetron sputtering

Abstract ZnS:Eu electroluminescent devices with a single insulating layer were prepared by r.f. magnetron sputtering. It was found that the optimum concentration of europium dopant in the sputtering target is 0.94 mol.%. The luminance level of this device is much lower than that of ZnS:Mn devices at a dopant concentration of about 1.0 mol.%. X-ray diffraction study shows that the crystallinity of ZnS:Eu phosphor is inferior to that of ZnS:Mn phosphor, which is a reason for the poor luminous characteristics of ZnS:Eu devices.

Bias Effects on Morphology and Growth Rate of Glow Discharge a-Si:H Films in a Triode System

We investigated the positive and negative bias effects on the morphology and the growth rate of a glow-discharge a-Si:H film prepared using a triode system. The growth rate increased with the magenitude of the bias, irrespective of its polarity. A columnar structure is promoted if the film is prepared with, an applied positive bias. The film is favorably densified if it is prepared with an applied moderate negative bias. An extremely high negative bias, however, leads to the formation of unfavorable nodules on the film surface. The configurational change of the incorporated hydrogen by the bias is discussed in terms of an inhomogeneous structure composed of a grain-boundary like region and a grain-like region.

Bias effects on preparation of amorphous silicon in a triode glow discharge

Abstract The effects on the growth rate and the film quality, including the content of incorporated hydrogen, caused by the enhanced ion flow due to a negative bias were examined using a triode glow discharge system in pure silane at a pressure of 0.22−0.4 Torr in which both features could be improved. The growth rate can be improved by using a negative bias only if the ion flow to the substrate is sufficiently enhanced. When the negative bias is moderate, the film quality is improved because of the promotion of SiH incorporation and/or the reduction in SiH 2 incorporation. When the negative bias is too high, however, a deterioration of the film quality is observed. This is due to the production of reactive species by collisions of energetic ions or electron impact dissociation in the plasma sheath around the substrate.

Improvement of the partial discharge resistance of polymer films by coating with plasma-polymerized films

The surface of polytetrafluoroethylene (PTFE) and polyethylene terephthalate films was coated with plasma-polymerized hexamethyldisiloxane (PPHMDS) film in a triode glow discharge system. The dielectric properties of PPHMDS films and their durability, the partial discharge characteristics and the surface morphology of coated polymer films were investigated. The lifetime of the coated PTFE films was longer than that of the uncoated PTFE films and varied with the preparation conditions of PPHMDS films. The maximum electrical pulse of the coated polymer film in a partial discharge electrode system was smaller than that of the uncoated polymer film. From observation of the deteriorated surface scars, it was shown that the PPHMDS film is effective for improving the partial discharge resistance.

Correlation between Adhesion Strength of Plasma-Polymerized Hexamethyldisiloxane Films to Polytetrafluoroethylene and Partial Discharge Resistance

Polytetrafluoroethylene (PTFE) films were coated with plasma-polymerized hexamethyldisiloxane (PPHMDS) films in a dc glow discharge system. The correlation between the adhesion of the PPHMDS films to the PTFE films and the partial discharge resistance of the composite films was investigated. The voltage endurance of the composite films in the presence of partial discharges increased with the adhesion of the PPHMDS films. From an observation of the deteriorated surface scars, it was shown that the deterioration is affected by the formation of cracks in the PPHMDS film.