Katsumi Aota

Growth of the 2223 Phase in Leaded Bi–Sr–Ca–Cu–O System

Growth of the 2223 phase has been studied in the leaded Bi-Sr-Ca-Cu-O system. Differential thermal analysis showed that the enhanced formation of the 2223 phase occurs in the temperature range between 835°C and 869°C where partial melting occurs. The density of the pellet was found to increase by 30% at one hour and then to decrease by 40% from the highest density attained. The former is attributed to the growth of the 2223 phase with the aid of the partially melted liquid phase and the latter to the flaky shape of the resultant 2223 crystals. The effect of Pb addition for enhanced 2223 phase formation will be discussed.

Growth of the 2223 Phase in Leaded Bi-Sr-Ca-Cu Oxide under Reduced Oxygen Partial Pressure

The growth process of 2223 phase in a leaded Bi-Sr-Ca-Cu oxide system has been investigated under various oxygen partial pressures using differential thermal analysis, combined with XRD of the quenched specimen. It is shown that under a slow heating rate, the DTA curves exhibit two or three endothermic peaks between 820 to 900°C, and the peak positions are lowered with reduction in the O2 partial pressure. The 2223 phase is found to grow most efficiently in the partial melting state sandwiched between the two endothermic peaks, and the temperature range between the two peaks becomes maximum around 0.1-atm O2 partial pressure.

A new mode of modulation observed in the Bi-Pb-Sr-Ca-Cu-O system

With the aid of transmission electron microscopy, the Bi-Pb-Sr-Ca-Cu-O system has been found to have a new mode of modulation in addition to the conventional one reported earlier in the Pb-free Bi-Sr-Ca-Cu-O system. The new modulation is observed in the perovskite {110} plane, as is the conventional one. The wave vector of the new modulation, however, is parallel to and the observed wavelength is about 50 A. Periodicities of the new as well as conventional modes of modulation become less regular in the Pb-added system. The disturbed modulation is argued in light of the strain energy relaxation due to the Pb addition.

Low-Temperature Growth of Silicon Dioxide Film by Photo-Chemical Vapor Deposition

Silicon dioxide films have been prepared from monosilane and oxygen gases using a low-pressure mercury lamp. The deposition rate is increased with UV irradiation and the activation energy is reduced to as low as 0.22 eV. The contribution of the 254 nm light to the deposition is concluded to be very small. The refractive index of the deposited film is 1.44~1.46. The infrared absorption peaks related with Si–H bonding do not appear in the photo-CVD film.

Photochemical vapor deposition of amorphous silicon through 185 nm excitation of monosilane

Abstract Photochemical vapor deposition of a-Si films at a high rate using SiH 4 and a 185 nm low pressure mercury lamp is described. A maximum rate of 1 nm/sec was attained using the 185 nm lamp. This rate was about ten times higher than that using a 254 nm lamp. Assuming that there is no interaction between the effects of the two wavelengths, the deposition rate per light output power of 184.9 nm light is 160 times larger than that for 253.7 nm light. The absorption cross-section of the 184.9 nm light is ten times greater than that for the 253.7 nm light.

Characterization of µc-Si:H Prepared by Photo-Chemical Vapor Deposition

Microcrystalline silicon deposited by photo-CVD is characterized to reveal dependence of crystallinity on the film preparation conditions. The volume fraction of microcrystalline (Xc) depends strongly on the dilution ratio of silane gas by hydrogen gas and substrate temperature (Ts) of deposition, while the grain size (δ) of the microcrystalline is kept conslant irrespective of deposition condition. Preferred orientation changes from (110) to (111) with increasing Xc.

Analysis of Deposition Rate Distribution in the Photo-CVD of a-Si by a Unified Reactor with a Lamp

The deposition rate distribution in the photochemical vapor deposition (photo-CVD) of hydrogenated a-Si films from monosilane or disilane by a unified reactor with a lamp has been investigated. When the distance between a gas outlet and a substrate is kept short, a characteristic distribution of deposition rate occurs because of the influence of a reactant gas flow. Such distribution can be explained by analyzing a rate equation which is represented by terms of generation, diffusion and extinction of activated species. If we assume the activated species are SiH2 or SiH3 radicals, the lifetime of activated species can be estimated as 0.02 s.