Yoshiki Ishizuka

Growth mechanism for (11n) orientations in Bi-Sr-Ca-Cu-O thin films

Abstract We have investigated the film growth mechanism for Bi-Sr-Ca-Cu-O (BSCCO). Effects of initial film growth stage and of substrate have been examined. Results show that (001) orientation is based on anisotropic growth kinetics for the crystal and that (11 n ) orientations are based on epitaxy between the perovskite layer in the crystal structure and a substrate, such as (110)SrTiO 3 and (110)LaAlO 3 . The epitaxy is based on a part of the crystal structure. Furthermore, (119) orientation is formed when the epitaxy is mainly influenced; (117) orientation is formed when the epitaxy and crystal structural stability have equal influence.

Crystalline orientation control for Bi-Sr-Ca-Cu-O thin films prepared on (110)SrTiO3 by coevaporation

Superconducting Bi-Sr-Ca-Cu-O thin films were prepared on (110)SrTiO3 substrates by coevaporation with an rf oxygen plasma. Four orientation categories were observed, the 2223-phase (119) orientation, the 2212-phase (119) orientation, the 2212-phase (117) orientation, and the 2212-phase (00n) orientation. It has been confirmed that these orientations can be controlled by changing the rf oxygen plasma conditions. The (00n) orientation grew as the oxygen flow rate increased or as the rf power increased.

Phase Control of Bi-Sr-Ca-Cu-O Thin Films Prepared by Coevaporation with RF Oxygen Plasma

Thin films of Bi-Sr-Ca-Cu-O were prepared on (100)SrTiO3 substrates by coevaporation with rf oxygen plasma. It has been confirmed that the structural phases of films can be controlled mainly by the flux density of activated oxygen and the substrate temperature, and not by the chemical compositions of the films. Thin films in the Bi2(Sr, Ca)3Cu2Oy phase and the Bi2(Sr, Ca)2CuOy phase were prepared by changing the flux density of activated oxygen and the substrate temperature. The films in the Bi2(Sr, Ca)3Cu2Oy phase showed superconducting transitions at 35 K.

Initial growth mechanism of BiSrCaCuO thin films on SrTiO3(110) surfaces studied by in-situ reflection high energy electron diffraction observation

Abstract The initial growth mechanism of Bi 2 Sr 2 Ca n −1 Cu n O x (BSCCO) films was investigated on SrTiO 3 (110) surfaces by in-situ reflection high energy electron diffraction (RHEED) observation. The orientations in the BSCCO thin films were controlled by the flux of metal elements in the initial growth stage. A preceding deposition of Bi produced a RHEED pattern indicating the formation of a bismuth oxide layer which assisted the growth of a half-unit cell at the beginning of codeposition. A ( Bi : Sr : Ca : Cu =) 2:2:1:2 phase (117) orientation mixed with a c axis orientation was obtained. A preceding deposition of Sr, Ca and Cu produced a pattern indicating the formation of (Sr 1− x Ca x ) 2 CuO 3 and caused epitaxial growth just after the start of codeposition, based on the structural relationship between the substrate and the perovskite structure part of the films. A 2:2:1:2 phase (119) orientation was formed.

Hg-Sensitized Photochemical Vapor Deposition Application to Hydrogenated Amorphous Silicon Photoconversion Layer Overlaid on Charge Coupled Device

An Hg-sensitized photochemical vapor deposition method has been developed which has enabled a hydrogenated amorphous silicon photoconversion layer to be overlaid on a charge coupled device (CCD) imager, without a pixel separation structure. This chemical vapor deposition (CVD) method has been used to realize imaging devices with high sensitivity and high resolution for high-definition TV.

Improvement of surface morphology and bulk structure of a-SiC:H films

Abstract The influence of gas flow and H 2 dilution ratio on the bulk and surface properties of a-SiC:H films is discussed. Infrared and electron spin resonance studies reveal that structural relaxation is achieved through control of surface reactions. On the other hand, the surface morphology as observed by atomic force microscopy is shown to be determined by growth rate under supply-limited conditions. This evidence implies that an improvement in bulk properties does not always lead to surface smoothening. Both surface reaction control and growth rate control are found to be crucial if films with excellent bulk and surface properties are to be obtained.

Predominant influences on the bulk properties and surface morphology in hydrogenated amorphous silicon carbide films

Abstract The influence of H2 dilution ratio, gas flow and substrate temperature on the bulk and surface properties of hydrogenated amorphous silicon carbide films is discussed. Through infrared and electron spin resonance studies, it is revealed that microstructural heterogeneity can be reduced by controlling surface reactions. On the other hand, atomic force microscopy observations reveal for the first time that surface morphology is dominated by growth rate under supply-limited conditions. This implies that improvement in the bulk properties does not always lead to films with smoother final surfaces. Both surface reaction control and growth rate control are found to be crucial for obtaining films with excellent bulk and surface properties.

The bias-annealing effect on a-Si:H photodiode

The bias-annealing effect has been investigated for a-Si:H photodiode. The characteristics of the photodiode have been successfully improved on μτ-product. The characteristics of transient photocurrent are also improved by bias-annealing at 125 and 150°C for around 100 h. The result of the transient photocurrent measurement reflects the density of states of the energy level at about 0.6 eV below the conduction band. The thermal current density increases with increasing bias-annealing time. According to the results, it is suggested that the density of states around midgap decreases and that above the Fermi level increases by the bias-annealing treatment. The result indicates that the neutral-charged defect converts to the negative-charged defect in case of a positive correlation energy.

Characteristics of a-Si:H films prepared by a novel laminar flow photo-chemical vapor deposition method

The a-Si:H films prepared by a laminar flow photo-chemical vapor deposition method were investigated. The Si-H 2 bond content (C SiH2 ) in the a-Si:H film and the relative residual current increased along the gas flow direction. The increases in C SiH2 and in the residual current are due to the increase in SiH 2 density. The SiH 2 is produced by a reaction between SiH 3 radicals during transport.

Film Growth Mechanism for Non-(001) Orientations in Bi-Sr-Ca-Cu-O

Thin films of Bi2Sr2CaCu2Oy were deposited on SrTiO3(110) substrates by coevaporation. It was confirmed that the chemical composition has a crucial effect on the growth orientation. The preferred orientation shifts from (119) to (117) as the Bi composition is increased. The difference in film growth kinetics is discussed from the viewpoint of an epitaxial relationship and crystal structural stability.