Shinji Migita

The influence of Bi-sticking coefficient in the growth of Bi(2212) thin film by ion beam sputtering

Abstract BSCCO thin films are fabricated via a co-deposition process by an ion beam sputtering method with an ultra-low growth rate, and sticking coefficients of the respective elements are evaluated. The sticking coefficient of Bi element exhibits a characteristic temperature dependence; almost a constant value of 0.49 below 730°C and decreases linearly with temperature over 730°C. This temperature dependence can be elucidated from the evaporation and sublimation rates of bismuth oxide, Bi2O3, from the film surface. It is considered that the liquid phase of the bismuth oxide plays an important role in the Bi(2212) phase formation in the co-deposition process.

Magnetic anomaly of Y1−xSrxVO3−δ

Abstract YVO3–SrVO3 system, in which the valence of vanadium ion varies depending on the contents of the oxygen and strontium ion, has been investigated magnetically and electronically to know the behavior of the strongly correlated electron. YVO3−δ, a Mott-type insulator with a perovskite structure, is found to exhibit an anomalous magnetic behavior and interpreted to be based on the parasitic ferromagnetism proposed by Dzyaloshinsky and Moriya [T. Moriya, Phys. Rev. 117 (1960) 635]. The energy gap and the intensity of the anomalous peak in the field cooling process are reduced with the increase of Sr molar fraction in Y1−xSrxVO3−δ.

Comparison between Bi-superconductor thin films fabricated via co-deposition and layer-by-layer deposition by ion beam sputtering method

Abstract Bi2Sr2CanCun+1Oy (n≥0; BSCCO) thin film is fabricated via two different processes using an ion beam sputtering method i.e. co-deposition and layer-by-layer deposition. A single phase of Bi2212 can be fabricated via the co-deposition process, while it cannot be obtained by the layer-by-layer process. Ultra-low growth rate in our ion beam sputtering system brings out the difference in Bi element adsorption between the two processes and results in only 30% adsorption against total incident Bi amount by layer-by-layer deposition, in contrast to enough Bi adsorption by co-deposition.

Molecular beam epitaxial growth of BSCCO and Bi-based oxides: self-limiting growth of the Bi element

Self-limiting function of Bi element in connection with experimental results of sticking coefficients of constituent atoms of BSCCO is described. Molecular beam epitaxial growth of Bi2Sr2CuOx (Bi2201) and Bi4Ti3O12 (BIT) is demonstrated using this function. A further advanced method and its growth results for Bi2Sr2CaCu2Ox (Bi2212) and Bi2Sr2Ca2Cu3Ox (Bi2223) growth are shown, where a chemical reaction between Bi2201 molecular layer and one or two monolayers of Ca and Cu deposited on Bi2201 is used. Estimation by means of X-ray diffraction, reflection high-energy electron diffraction, and atomic force microscopy shows excellent quality of the films obtained. Heteroepitaxial growth of BIT/Bi2201 using the self- limiting function of Bi is also done.

Is It Possible to Obtain Easily Single Phase of BSCCO Thin Film

Phase intergrowth in BSCCO thin films have been investigated. It turned out from XRD analyses of these phases that molar fraction of each constituent phase in the intergrowth thin film can be exhibited as a function of substrate temperature and ozone pressure. Superconducting behavior of the intergrowth thin film is also discussed.

Effects of Growth Rate In Fabrication of Bi2212 and Bi2201 Thin Films

In order to make the quality of the Bi-superconducting thin film better, the relationship between thin film quality and several growth conditions such as growth temperature, ozone pressure, composition and growth rate are examined in reactive co-deposition method. Compositional region and suitable substrate temperature for phase stablity are established, and it is found out that the surface morphorogy is improved by lower growth rate.

Co-deposition and Layer-by-layer Deposition for Bi-superconducting Thin Film Using Ion Beam Sputtering Method

BSCCO thin film is fabricated via both processes of co-deposition and layer-by-layer deposition at an ultralow growth rate using ion beam sputtering method. The adsorption of Bi atom and the appearance of Bi2212 phase shows large difference between both processes. It is found that the resident time of Bi vapor species on the surface of the substrate strongly dominates the film composition and the formation of the structure.

Evaluation of the Ozone Density Condensed by an Adsorption Method Using Thermal Decomposition

An ozone condenser by a selective adsorption on the silica gel surface is constructed. Ozone density is evaluated by three methods; ultraviolet absorption, thermal decomposition and Q-mass analyzing methods. Thermal decomposition method is found to be available to the density evaluation from dilute to highly condensed ozone. The highest ozone density condensed by the adsorption method is evaluated to be 97mol%.

Epitaxial Growth of BSCCO Type Structure in Atomic Layer by Layer Deposition by Ion Beam Sputtering

Bi2Sr2CuOx(Bi(2201)) thin films are fabricated by atomic layer by layer deposition using ion beam sputtering (IBS) method. During the deposition, 10%-ozone /oxygen mixture gas of typical 5.0 × 10−5Torr is applied with ultraviolet light irradiation for oxidation. XRD and RHEED investigations reveal out that a buffer layer with some different compositions is formed at the early deposition stage of less than 10 units cell and then c-axis oriented Bi(2201) is grown.

Syntheses and Physical Properties for Tl-Sr-V-O System

Tl-Sr-V-O system was investigated to search for new non-Cu and n-type superconductors. A ferromagnetic behavior, however, was observed in Tl-Sr-V-O system and a remarkable hysteresis between ZFC and FC processes was found. A new peak at 2 θ =6.8° which suggests a long periodical structure was found.