Excess Bi Research Articles

Ｂｉ，Ｃｒ添加Ｍｎ２Ｓｂ垂直磁化膜の作製と磁気および磁気光学特性

Mn2Sb films prepared by vacuum evaporation are known to form perpendicularly magnetized films. The doping effect of Bi and Cr in Mn2Sb films on magnetic and magneto-optical properties was investigated over a large amount of doses up to 26 at.% for Bi and 16.4 at.% for Cr. Perpendicular magnetization characteristic maintains even at such heavy doped films but the substitution of Bi for Sb is estimated to be about 8 at.% in Mn2Sb and the excess Bi is precipitated at the free surface of the films from magnetic and AES measurements. Magneto-optical Faraday rotation angle at λ=633 nm is decreased by increasing the amount of the dose. As Bi and Cr modified Mn2Sb intermetallic compounds are known to have the first order phase transition from anti-ferromagnetism to ferrimagnetism, these films (especially Cr doped films) may be applicable to temperature sensor by making use of the phase transition temperature.

Surface structure and oxidation of Si(001) [sbnd]Bi

The geometric structure, electronic state and reaction with O 2 of the Si(001) surface with Bi overlayer have been studied by LEED, XPS and UPS. Bi(0001) was grown epitaxially with interface structure of Bi(0001) Si(001) and Bi[2110] Si[110] when Bi was deposited on Si(001)2 × 1 clean surface at room temperature. Subsequent annealing to 570–720 K caused the desorption of Bi, and successive phase transition of the 2 × n (10 > n > 5) surface structure was observed around 1 ML (i.e. atomic ratio of Bi to first layer Si is unity). The effect of an O 2 exposure of 1000 L at 570–720 K depended upon initial Bi coverage. At submonolayer Bi coverage, O 2 exposure induced the oxidation of Si surface and the desorption of Bi. On the other hand, the 2 × n surface which corresponded to about 1 ML were stable against O 2 , indicating strong interaction between Bi and Si. At higher coverage, excess Bi atoms were oxidized.

Superconducting (Rb,Ba)BiO 3 thin films grown by molecular beam epitaxy

Abstract The simple cubic perovskite (Rb,Ba)BiO 3 can be grown by molecular beam epitaxy using an RF plasma oxygen source. Films with superconducting onsets in resistivity as high as 27K are obtained without annealing. The epitaxy proceeds in the normal (1 0 0) orientation on (1 0 0) SrTiO 3 , despite a 10% lattice mis-match. (1 1 0) epitaxy is obtained on (1 0 0) MgO substrates, despite the good lattice match for (1 0 0) growth. The films with the lowest normal state resistivity are those grown on SrTiO 3 at 300±10°C and are Bi deficient despite excess Bi flux during growth. The temperature dependence of the resistivity for these films is metallic down to T c . H c2 for a T c =20K film is 10±T.

Solid-state reaction of Ru and Al in molten Bi

There has been much recent interest in the reactions that occur when two crystalline metals inter-diffuse at low temperatures. Metastable phase formation can occur when structural relaxation into equilibrium crystalline phases is kinetically inhibittedf. These reactions are typically studied in thin—film diffusion couples formed by sequentially depositing two elemental crystalline metals. In this paper we describe a novel low—temperature reaction sequence for the formation of very fine-grain Alx Ru,1-xalloys that allows a further extension of these techniques. This reaction regime uses molten Bi as a medium for the transfer of Al solute atoms to the surface of Ru powder where reaction occurs with the formation Alx Ru1-x,intermetallic phases. The low melting point and ease of handling of Bi, its solvent ability towards Al and Ru, the absence of equilibrium phases of Bi with Al and Ru, and previous experience in our laboratory with equilibrium and metastable phase formation in this system made it attractive as a prototype for this initial study.Ru powder and Al pellets were separatedly prereacted in molten Bi at 500 C for several hours to ensure wetting of the solid surfaces. This Ru and Al and additional excess Bi were then sealed together in a fused silica tube and reacted in a vertical tube furnace. Separate such reactions were carried out at temperatures ranging from 300 to 600 C. After reaction samples were broken free from the fused silica tube and the Bi transfer medium was etched away in concentrated HNO3.

SYNTHESIS OF SUPERCONDUCTING Bi-Sr-Ca-Cu-O OXIDES VIA MECHANICAL ALLOYING

Bi-Sr-Ca-Cu-O superconductors have been prepared from the constituent pure metals by mechanical alloying in air and succeeding sintering at high temperatures in flowing oxygen. X-ray patterns from the milled powders indicate that the dissolution of excess Cu and Bi in the Bi-Sr-Ca-Cu matrix occurs progressively with milling. However, a prolonged milling resulted in amorphous-like diffraction patterns with the first peak centered around 30°. The particle size rapidly asymptotes to a fixed value near 30 h milling. The X-ray patterns of the sintered materials are in good agreement with those of the orthorhombic structure reported in the superconducting Bi-base oxides. The low Tc phase in the Bi-base oxides was identified from the resistivity and susceptibility measurements. The superconducting temperature appears to be sensitive to the milling conditions.

Indirect Trace Determination of Ethylenediminetetraacetic Acid (Edta) in Water by Potentiometric Stripping Analysis

Abstract An analytical method for indirect trace determination of ethylenediaminetetraacetic acid (EDTA) in water, by potentiometric stripping analysis is described. Excess Bi(III) was added to form a 1:1 complex with EDTA at pH 2.3. The uncomplexed Bi(III) was then deposited on a glassy carbon electrode at a potential of −0.40 V vs. SCE and subsequently stripped potentiometrically using potassium dichromate as oxidant. The stripping time of uncomplexed Bi(III) was recorded. The Concentration of EDTA in the sample was determined from the concentration of added Bi(III) and the potentiometrically stripped Bi(III) at −0.4 V by the standard addition method. The relative standard deviation for EDTA concentration of 95 ppb and 4.5 ppb was 1.9% and 2.6%, respectively. The detection limit was about 1 ppb EDTA for a deposition time of 3 minutes.

ChemInform Abstract: Preparation and Lattice Parameters of Americium and Curium Monobismuthides.

Abstract243AmBi and 248CmBi have been prepared from the elements (vacuum, excess Bi; AmBi: 700 °C, 16 h; CmBi: 400‐600 °C, several h).

Superconducting BaPb1-xBixO3 Thin Films by RF Magnetron Sputtering

RF planar magnetron sputtering has been adopted for obtaining superconducting BaPb1-xBixO3 (BPB) thin films. Using a target with excess Pb and Bi, smoothly surfaced BPB films with Tc above 9 K were obtained at a deposition rate as high as 400 Å/min. It was found that the film properties do not strongly depend on sputtering pressure and voltage as compared with that of the conventional sputtering method. Furthermore, the reproducibility has been greatly improved.

Indium antimonide-bismuth compositions grown by molecular beam epitaxy

Thin films of InSb-InBi solid solutions have been prepared by molecular beam epitaxy. Using in situ reflection electron diffraction, conditions for epitaxial growth of stoichiometric layers were established on (001) and (110) surfaces of both InSb and GaAs wafers. Bi is shown to modify the diffraction patterns of (001) InSb from C(8×2) and (√2×√2) 45° to (1×3). Surface residence times of Bi were found indefinitely long (≳10 min) at temperatures ?420 °C. Bi incorporation into InSb during growth by molecular beam epitaxy is strongly dependent on Bi surface concentration, and influenced by substrate temperature and surface nonstoichiometry. Secondary ion mass spectrometry depth profiling and 2.5 MeV ion dechanneling spectra showed that ∼3% Bi can be incorporated substitutionally in Sb sites, under In rich growth conditions (largest available concentration of VSb sites). Increased Bi surface accumulation and interstitial incorporation are observed under Sb-rich surface conditions and as the relative flux of Bi is increased. Excess surface Bi forms liquid alloys with excess In during growth above 280 °C which alters the incorporation. These alloys solidify on the surface of grown films on cooling. Absorption cut-off wavelengths are unaffected by interstitial Bi concentrations; however, cutoffs out to ≳9.5 μm at 77 K are observed for Bi-doped films grown under In-rich conditions.

Preparation and properties of superconducting BaPb1−xBixO3 thin films by sputtering

Superconducting thin films of BaPb1−xBixO3 with transition temperature above 9 K were successfully prepared by rf diode sputtering and subsequent annealing. It was found that sputtered films tended to lack Pb and Bi during deposition, so that targets with excess Pb and Bi were used in order to achieve the film stoichiometry. Sufficient oxygen partial pressure during discharge was found to be requisite for obtaining thin films with low resistivity, high Tc, and sharp superconducting transition. The films admit optical transmission to a small extent in the wavelength range from 500 to 700 nm. Based on these results, some aspects of the band structure are discussed.

The electrical conductivity of bismuth chalcogenides in the liquid state

AbstractThe electrical conductivities of liquid BiTe and BiSe systems are measured as a function of temperature. Plots of the electrical conductivity and its temperature derivative versus composition for liquid BiTe system give a relatively smooth curve near the stoichiometric composition of Bi2Te3. The electrical conductivity of the liquid BiSe system is considerably small compared with liquid BiTe system. The temperature dependence of the electrical conductivity indicates that the liquid BiSe system becomes metallic rapidly with increasing Bi content beyond the composition of Bi2Se3. The impurity doping (Bi, Ga, and In) effects are investigated on Bi2Se3 melt using both the electrical conductivity and the magnetic susceptibility. The results of Bi‐doped melts suggest that a complete ionization occurs of the excess Bi atoms, whereas an appreciable non‐localization of valence electrons is seen in alloys containing excess Ga and In atoms.

The production of dithionite and SO 2− by chemical reaction of (bi)sulphite with methyl viologen semiquinone

Methyl viologen semiquinone has been shown to react chemically with excess (bi)sulphite to form oxidized methyl viologen, dithionite and SO2−. When methyl viologen is maintained in its reduced form with hydrogen and hydrogenase, the dithionite formed increases with the square of the (bi)sulphite concentration, and it also increases with decreasing pH in the range pH 6–8. It is proposed that this redox equilibrium may be important in determining the product composition in assays for (bi)sulphite reductase.

Optimization of epitaxial quality in sputtered films of ferroelectric bismuth titanate

Earlier phases of this study demonstrated the feasibility of growing epitaxial films of Bi 4 Ti 3 O 12 by rf sputtering from ceramic targets containing excess Bi 2 O 3 . These films were unsuitable for device exploitation of the unusual electro-optic display properties of bulk crystals of the titanate because of their twinned, multidomain character. During the present phase, clamping effects exerted by the MgO substrate were shown to prevent conversion by electrical poling to the single domain state. Other substrates were investigated, TiO 2 and sapphire giving the (001) orientation desired for the differential retardation display mode, and MgAl 2 O 4 giving the (010) orientation required for the extinction mode. The latter is obtained untwinned, a result attributed to the thermal expansion and lattice mismatch properties of the system, which, however, also lead to cracking and peeling due to large stresses along the film c -axis. The peeling problem was alleviated by a novel stress compensation growth technique resulting in films on MgAl 2 O 4 , showing minimal substrate clamping effects, and good electro-optic switching properties.

Filling-in of the pseudogap in amorphous Mg—Bi alloys

The optical properties of amorphous Mg-Bi alloys have been studied in the near infrared and visible spectral regions. Amorphous Mg 3Bi 2 is found to be a semiconductor with a band gap of 0.152 ± 0.005 eV. Excess Mg or Bi in amorphous Mg 3 Bi 2 is shown to form localised states near the Fermi level which fill in the pseudogap. These results are inconsistent with the rigid band model proposed by Ferrier and Herrell.

PREPARATION AND PROPERTIES OF EPITAXIAL FILMS OF FERROELECTRIC Bi4Ti3O12

Sputtered films of ferroelectric Bi4Ti3O12 have been prepared by using targets containing excess Bi to compensate for loss of Bi in the deposition process. Epitaxial growth has been achieved on MgO and epitaxial Pt substrates. Studies of dielectric properties suggest that the sputtered films are suitable for use in high-capacitance structures. Hysteresis measurements yield spontaneous polarization values for the epitaxial films which are in excellent agreement with those reported for bulk single crystals.

Bismuth–Tellurium Photo-voltaic p–n ‘Sandwich’ Layer

IT has been fairly well established1,2 that bismuth telluride changes conductivity type1,2 with the excess of tellurium over stoichiometric proportion between 1 and 2 atomic per cent3. It has been assumed that each excess Bi(Te) atom replacing the Te(Bi) atom in the single crystal of Bi2Te3 behaves as an ionized acceptor (donor)1–3.