Sachio Ishioka

Control of Optical Gap in a-SixC1-x: H Alloy Films Produced by Reactive Sputtering Method

Hydrogenated amorphous silicon-carbon alloy (a-SixC1-x: H) films are prepared by simultaneous if reactive sputtering of silicon and graphite in a H2–Ar gas mixture. The optical gap E0 of a-SixC1-x: H depends on alloy composition x and preparation conditions. The optical gap E0 of a-SixC1-x: H prepared under a same condition is ~1.7 eV at x=1.0 (a-Si: H), increases with the decrease in x, reaches a maximum value of 2.2 eV at x=0.6 and then decreases with decrease in x, reaching ~1.4 eV at x=0 (a-C: H). For films prepared at lower substrate temperature, the optical gap becomes larger. This behavior of the optical gap is discussed referring to the results of X-ray photoemission spectroscopy, infrared absorption measurements, etc., on a-SixC1-x: H.

Single-Tube Color Imager Using Hydrogenated Amorphous Silicon

Reactively sputtered hydrogenated amorphous silicon film is used as the photoconductive target of a vidicon type image pickup tube. It is indicated that hydrogen partial pressure in the discharge gas has to be 40% or more in order to attain suitable image pickup tube characteristics. Photo-electric properties and lag-characteristics are enormously improved by lightly doping boron into amorphous silicon film, and a blocking type target structure is effective for suppressing dark current of the pickup tube. Using doped amorphous silicon film with a color-filter-integrated face plate, a single-tube color imager is fabricated.

Determination of traces of boron in semiconductor amorphous silicon film by filament-vaporization inductively-coupled plasma/atomic emission spectrometry

Abstract Silicon is dissolved from the platinum substrate by nitric/hydrofluoric acids. The recovery of boron on direct analysis was poor, but was increased to >95% by the addition of 500–5000 μg ml −1 phosphorus as phosphoric acid. The results compared well with the molar ratio of the gases (B 2 H 6 /(Ar + H 2 ) used to form the film and the intensity ratio of 11 B + and 30 Si + obtained by secondary-ion mass spectrometry.

Amorphous Silicon Image Pickup Devices

Reactively sputtered amorphous silicon film is used as a photoconductive target of the vidicon type image pickup tube. Variation of tube characteristics with the hydrogen partial pressure in the discharge gas during sputtering are investigated. The results indicate that hydrogenated amorphous silicon films prepared in hydrogen partial pressures of 1~2×10-3 Torr are suitable for image pickup tubes. This amorphous silicon vidicon has several excellent characteristics: better sensitivity of about twice that of the conventional tubes, high resolution, little after-image, and no blooming.

Amorphous Silicon Image Pickup Tubes

Reactively sputtered a-Si:H is used in a photoconductive target of an image pickup tube. When a-Si:H is used for a color imager, high resistivity and wide optical band gap are required. A blocking type target structure is effective in reducing dark current and producing rapid photo response. Low doping of boron into a-Si:H serves to increase both hole and electron mobilities. The imaging tube using this a-Si:H has high photosensitivity, high resolution, and no sticking or burning. By using high velocity electron beam for scanning, lag property is drastically improved.

Chapter 5 Image Pickup Tubes

Publisher Summary This chapter describes the use of hydrogenated amorphous silicon (a-Si:H) in imaging tubes. The a-Si:H is a photoconductor having the vacuum side charged to cathode potential. Light causes charge leakage during a frame time; the signal is the electron-beam current needed to recharge the surface. Blocking contacts are used to reduce the leakage current. Hydrogenated amorphous silicon has a broad spectral response that is especially sensitive in the visible range. The signal current is proportional to the light intensity at all wavelengths, which simplifies color balancing. The spatial resolution is comparable to that of commercial vidicons and exhibits neither blooming nor image burning under strong illumination. When used to intensify x-ray images, the a-Si:H imaging tube has a better resolution than conventional image intensifiers. A single-tube color camera has been demonstrated using striped color filters on the face plate. The decay lag in a-Si:H tubes is presently 4%, and it is necessary to reduce this lag, especially to apply the technology to broadcasting use.