Keiichi Ando

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.

Current efficiency in the plasma anodization of aluminium

Abstract By analysis of the current-voltage characteristics of Al-plasma-anodized Al 2 O 3 -plasma systems the high field conduction characteristics of plasma-anodized thin Al 2 O 3 films in the plasma were found to be expressed by the equation J s = J f0 exp(BF) (where J s is the specimen current density, F the electric field strength across the oxide film and J f0 and B are constants); in this experiment B and J f0 were (1.1-1.4)×10 -6 cm V -1 and about 10 -8 A cm -2 respectively. It was ascertained that the current efficiency in the plasma anodization of aluminium becomes a maximum when the surface potential of the specimen is equal to the plasma space potential. From this it was deduced that most of the negative oxygen ions contributing to plasma anodization are generated by the ionization of oxygen atoms adsorbed on the surface of the specimen.

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.