Diffusion Of Bi Research Articles

Time dependence of electrical properties of SrBi 2Ta 2O 9 thin films after top electrode annealing

The time dependence of electrical properties of SrBi 2Ta 2O 9 (SBT) thin films after top electrode annealing was studied. The high leakage current density was measured immediately after the top electrode annealing but leakage current characteristics were improved with increasing time. In C– F characteristics, the low frequency dielectric dispersion was also observed and the dispersion frequency moved to low frequency due to the increase of the interface resistance. The time dependence of electrical properties can be explained to be due to the gradual decrease of the conductivity of (semi)conducting paths. The conducting path may be formed by the diffusion of metallic Bi and the reduction of Bi oxide during the top electrode annealing and its conductivity may be decreased due to the interaction of metallic Bi with oxygen atoms after the stabilization.

Atomic Scale Grain Boundary Analysis by Incoherent Imaging With TEM/STEM

Abstract Quantitative compositional characterization was carried out on a ceramic boundary using atomic resolution high-angle annular dark field scanning transmission electron microscopy (HAADFSTEM), with the aid of HAADF image simulation. HAADF-STEM observation was performed with a JEM-2010F TEM/STEM equipped with a field emission gun and an HAADF detector. And also the image simulation for HAADF was made on a computer by the program that was developed by the authors using Bethe's method. The material used in this experiment that was provided by TDK Co., is a semiconducting SrTiO3 (STO) ceramic condenser. The bulk substance was formed by the process of sintering in a reduced ambience followed by the reoxidization in the air after surface coating with Bi2O3, PbO and CuO compounds resulting in having a unique structure with Bi diffusion layers at the grain boundary region.

Diffusion of Cu into the Ag sheath of BPSCCO tapes

Diffusion studies of (Bi,Pb) 2Sr 2Ca 2Cu 3O 10 (2223) tapes wrapped in Ag show that Cu of the 2223 ceramic diffuse into the Ag sheath during annealing resulting in a decrease of the Cu content of the ceramic. The diffusion coefficient has been determined to be 1.8×10 −11 cm 2/s at 815°C. In Ag–Mg alloy the diffusion coefficient appears to be about two orders of magnitude faster. Mass balance calculations show that the Cu content of the ceramic decreases by about 8.5% considering an Ag:2223 ceramic ratio of 80:20 which is frequently used for 2223 tapes. A diffusion of Bi, Pb, Sr and Ca into Ag has not been observed.

Photoconductive Bi12MO20-type films prepared by pulsed laser deposition

Bi12TiO20 (BTO); Bi12GaxBi1−xO19.5 (BGaO); and Bi12(M1/3P2/3)O20, M = Cd, Zn, and Ni (BMPO) thin films were prepared by pulsed laser deposition using a KrF excimer laser on (100)Y-stabilized zirconia (YSZ), (100)Bi12GeO20 (BGO), and (110)Bi12SiO20 (BSO) crystalline substrates. All these films have a sillenite structure. On (100)YSZ the sillenite is oriented as {310} with the 〈130〉 direction parallel to the 〈021〉YSZ directions (〈130〉{310}BTO〈021〉{100}YSZ). On (100)BGO and (110)BSO the sillenite film reproduces the substrate orientation, and the films formed are able to channel He+ particles. The optimum deposition temperatures for BTO and BGaO are 600 and 550 °C, respectively. Higher temperatures must be avoided to minimize the nucleation of Bi-deficient phases due to the diffusion of Bi into the YSZ substrates. BMPO films are polycrystalline. The lattice parameters of these films were determined. The crystalline films support guided optical modes. The refractive indices obtained for the films are close to those measured in bulk crystals, being slightly larger for films deposited on isomorphous sillenite substrates. The crystalline films deposited on YSZ are photoconductors when excited in the green and blue spectral regions.

Influence of Grain boundary Layers on the Dielectric Relaxation of Nb-Doped SrTiO3

The dielectric relaxation of Nb-doped SrTiO3 in the temperature range of 500–900 K was investigated to understand the effect of space charge in grain boundary layers. The dielectric relaxation phenomena were observed for all specimens, regardless of the doping content of Nb. The permittivity maximum temperature (Tεm) shifted and the permittivity peak height varied with the doped content of Nb. In order to study the effect of space charge in the grain boundary on the dielectric relaxation, Bi ions were diffused along the grain boundary of a 0.6 mol% Nb-doped SrTiO3 specimen. It was found that the dielectric relaxation behavior changes with the diffusion of Bi. These relaxations can be explained in terms of the space charge, which is varied by defects, in grain boundary layers.

Effects of reduced growth temperature on crystalline qualities and dopant diffusion in Pb 1− xSn xSe/PbSe layers grown by MBE

The MBE growth of lead tin selenides (Pbi 1− x Sn x Se: LTS)/PbSe double layers was carried out, and the effects of reduced growth temperature on crystalline qualities of upper LTS layers and diffusion of dopants at the interface between LTS and PbSe were investigated. A few micrometer-thick PbSe epitaxial layers (undoped) were directly grown on the CaF 2 (111) substrates at 485 °C and then the Bi or Bi 2Se 3 doped LTS layers were grown on top of PbSe at 200–485 °C. It was found that epitaxial temperature could be reduced to 200 °C. Reflection high energy electron diffraction (RHEED) patterns and full width at half maximum (FWHM) values of X-ray rocking curves in LTS indicated that crystalline qualities of LTS layers tended to degrade at lower temperature than ~ 300 °C. Deviation from the abrupt change in dopant concentrations at the interface was observed by secondary ion mass spectroscopy (SIMS) analysis, suggesting possible diffusion of dopant from LTS into PbSe. In the case of diffusion of Bi from LTS ( n ~ 10 18 cm −3) into undoped PbSe ( p ~ 10 17 cm −3), deviation was as small as 500 Å and the value of diffusion coefficient was roughly estimated as that of the order of 10 −15 cm 2/s at 300–400 °C.

Grain-Boundary Diffusion of Bi in Cu Bicrystals

The diffusion of Bi along various [011] and [001] twist and [001] symmetric tilt boundaries of Cu has been investigated as a function of the misorientation angle. For the three types of grain boundary, a close correlation is found between the diffusivity of a boundary and the energy of the boundary. The minimum of the boundary diffusivity occurs where the cusps of the boundary energy exist. The larger the degree of disorder in the atomic arrangement at a boundary, the higher is the boundary diffusivity. The diffusion in the [011] twist boundaries takes place more easily than that in the [001] twist boundaries.

Diffusion of Bi into ZnO Film Prepared by CVD and Its I-V Characteristics

Diffusion of Bi into ZnO Film Prepared by CVD and Its I-V Characteristics

Misorientation dependence of diffusion of Bi in [0 0 1] symmetric tilt boundaries of Cu

Misorientation dependence of diffusion of Bi in [0 0 1] symmetric tilt boundaries of Cu

Pattern-formation study of macroscopic dense branching morphology in Bi0.69Al0.27Mn/SiO films.

A centimeter-sized dense branching morphology (DBM) has been observed in thermally annealed Bi/Al/Mn/SiO multilayers, and is studied thoroughly by using various examination means. I suggest that the observed DBM is caused by the self-organization behavior of magnetic domains, that is, magnetic domains with perpendicular magnetization are separated from the matrix and coagulated into branches. Intensive diffusion and segregation of the low-melting-point element Bi are found to play critical roles in the pattern formation. Further segregation of Bi on a DBM induces a dendriticlike structure of fractal character. Atomic diffusion and surface accumulation of Bi on a SiO layer lead to surface terraces and color DBM images. A method is proposed to deduce the DBM growth kinetics, and our results show that the DBM observed in our case nearly follows the constant-velocity growth mode as well. \textcopyright{} 1996 The American Physical Society.

Integration Aspects and Electrical Properties of SrBi2Ta2O9 for Non-Volatile Memory Applications

AbstractHighlights and solutions to some of the challenges involved in integrating SrBi2Ta2O9 (SBT) capacitors with Pt electrodes on silicon wafers for non-volatile memory applications are discussed. These include the diffusion of Bi through the Pt bottom electrode during firing, capacitor patterning, and process damage that results from hydrogen containing atmospheres.Next, studies of the temperature dependence of many of the important electrical properties of SBT are presented. These include the remanent polarization (2Pr), the non-volatile polarization (Pnv), and the coercive field (Ec) all of which are studied as functions of the pulse amplitude; fatigue resistance of 2Pr and Pnv; the retention; the small signal capacitance versus voltage behavior; and the current versus voltage behavior. These studies demonstrate that SBT looks very promising for ferroelectric non-volatile memories over the consumer application range (0 to 70 °C).

Diffusion of both Ga and Bi into InSb seeds during growth of InGaSbBi

In1−xGaxSb1−yBiy (0<x≤0.21, 0<y≤0.005) quaternary bulk single crystals were grown on InSb seed crystals using a rotary Bridgman method. In order to investigate the quality of these crystals, various kinds of measurements were carried out, such as optical microscope, x-ray topograph, four-crystal x-ray diffractometry, electron-probe microanalysis, energy-dispersive spectroscopy, and secondary-ion-mass spectroscopy. All grown crystals were 10 mm in diameter and more than 10 mm in length. This indicates that the rotary Bridgman method was useful to grow quaternary bulk single crystals. Owing to segregation, the compositional ratio of Bi (y) increased and that of Ga (x) decreased as crystals grew. During growth of InGaSbBi, both Ga and Bi diffused into the InSb seed and there appeared domains of InBi. For comparison, InSb1−yBiy (0<y≤0.05) and In1−xGaxSb (0<x≤0.16) were grown on InSb. It turned out that Bi did not diffuse into InSb without Ga, but Ga diffused without Bi. The incorporation of Ga produced the excess In and as a result InBi domains were formed.

Highest Brain Bismuth Levels and Neuropathology Are Adjacent to Fenestrated Blood Vessels in Mouse Brain after Intraperitoneal Dosing of Bismuth Subnitrate

A small fraction of humans ingesting bismuth (Bi)-containing medications develops neurotoxicity in which neuropsychiatric signs precede motor dysfunction. Large ip doses of Bi subnitrate (BSN) produce similar signs in mice, but little is known about the pathogenesis of neurotoxicity in either species. Adult female Swiss-Webster mice received a neurotoxic dose (2500 mg/kg ip) of BSN. Bi distribution and neuropathology were determined as follows: (1) Regions of central and peripheral nervous system were assayed for Bi by atomic absorption spectrometry (AAS) 28 days after dosing, (2) regional brain Bi distribution was demonstrated in histologic sections by autometallography 28 days after dosing, and (3) blood/brain barrier status and neuropathologic effects were evaluated by light and electron microscopic techniques 1, 3, and 7 days and 2, 3, 4, and 5 weeks after dosing. By AAS, Bi levels were highest in olfactory bulb (∼7 ppm), hypothalamus (∼7 ppm), septum (∼3 ppm), and brain stem (∼3 ppm). Striatum and cerebral cortex had the least Bi (∼1 ppm). Regional distribution by autometallography showed that high Bi levels were associated with diffusion of Bi from fenestrated blood vessels of circumventricular organs and olfactory epithelium. All treated mice had hydrocephalus, but no other pathology was demonstrable by light microscopy. By electron microscopy, dramatic expansion of the extracellular space between choroid plexus epithelial cells was observed. Dendrites in the neuropil of the hypothalamus and septum exhibited vacuoles and membranous debris. Based on the Bi distribution and lesions, we propose that diffusion of Bi from fenestrated blood vessels contributes to pathogenesis of neurotoxicity in mice. This proposal is consistent with the clinical features of Bi-related neurotoxicity in humans.

Diffusion of bismuth and gold in nanocrystalline copper

Measurements of Bi and Au diffusion in nanocrystalline (n-) Cu and of Bi in copper thin films have been performed. The results show that (a) the diffusivity in n-Cu can be enhanced by more than ten orders of magnitude with respect to that in single-crystalline Cu. (b) Grain boundaries in n-Cu have a higher free energy and volume than conventional grain boundaries. (c) Relaxation can take place in n-Cu. (d) Diffusion measurements in n-materials represent a convenient means to determine thermodynamic properties such as grain boundary energies, solubilities, heats of segregation, and solution.

Sintering and microstructural development of metal oxide varistor ceramics

Anomalous retardation of the sintering kinetics of ZnO with addition of Bi 4Ti 3O 12 (BIT) and a low voltage varistor composition containing ZnO, BIT, Co 3O 4 and Mn 2O 3 in the temperature interval between 780 and 850°C was investigated. On the basis of transmission electron microscopic analysis of diffusion couples the retardation of sintering kinetics was ascribed to surface diffusion of Bi and Ti along ZnO grain surfaces. Liquid phase formation resulting from chemical reactions between the components triggers exaggerated grain growth. Nucleation and growth of anomalous grains is influenced by the presence of inversion boundaries in ZnO grains.

Size Effects in Ruthenium-Based Thick-Film Resistors: Rutile vs. Pyrochlore-Based Resistors

The size effect, namely the change of sheet resistance, Rsas a function of resistor length, has been investigated in layers whose conductive phase evolves from Pb-rich (Ru-deficient pyrochlores) to Pb2Ru2O6.5and finally to RuO2by increasing the firing temperature. It is found that Bi diffusion from the terminations is responsible for lower sheet resistance values in shorter resistors whatever the conductive phase is. On the contrary, Ag diffusion is responsible for lower sheet resistance values in shorter resistors only in the case of ruthenate conductive grains while the reverse is observed in RuO2-based layers. Size effect can be suppressed with Pt/Au-based terminations provided that no Bi is contained and with Au-metallorganic-based contact provided that the peak firing temperature is not too high.

Range and thermal-behavior studies of Au and Bi implanted into photoresist films.

The Rutherford backscattering technique has been used to determine range parameters of Au and Bi ions implanted into AZ1350 photoresist films at energies from 20 to 300 keV. The experimental results are 20 to 25% higher than the theoretical predictions by Ziegler, Biersack, and Littmark. Good agreement is achieved only when inelastic effects are included in the nuclear stopping-power regime. In addition, we find that shallow implantation of Bi ions increases the temperature at which the photoresist starts to decompose. This feature is not observed when Au is implanted under the same conditions. Finally, we have studied the thermal behavior of implanted Bi and Au ions. While Bi diffuses regularly, Au does not follow an Arrhenius kind of behavior. In addition, it is shown that the implantation process modifies, via the nonannealed damage, the characteristics of the Bi diffusion behavior.

Thermal stability and Bi diffusion in the implanted AZ111 photoresist: R B Guimarāes et al,Nucl Instrum Meth Phys Res,B32, 1988, 419–421

Thermal stability and Bi diffusion in the implanted AZ111 photoresist: R B Guimarāes et al,Nucl Instrum Meth Phys Res,B32, 1988, 419–421

Thermal stability and Bi diffusion in the implanted AZ111 photoresist

The Rutherford backscattering technique has been used to study the thermal stability modifications induced by the ion implantation process. In agreement with previous results, it is observed that a nonimplanted AZ111 photoresist film starts to decompose at 200 ° C. On the other hand the same film after being shallowly implanted with a low dose of Bi ions remains stable up to 350 ° C. In addition it is observed that Bi diffuses preferentially towards the bulk. At 300°C two different diffusion coefficients are estimated, one for the damaged region D d = 1.2 × 10 −15 cm 2/ s, and another for the bulk D b = 1.2 × 10 −14 cm/ s. It is suggested that both phenomena, the inhibited diffusion in the implanted region and the elevation in the stabilization temperature of the polymer, should be related to the damage produced by the implantation.

Implantation and thermal annealing behaviour of Bi imlanted into the Al/KCl bilayer compound

Abstract A bilayer system composed of an Al 610 A film evaporated onto a KCl single crystal and a pure KCl single crystal were both implanted with 300 keV 209Bi+. The Bi depth distribution agrees with the Monte-Carlo simulation predictions in both systems. Diffusion of Bi in the Al film and in the KCl substrate of the Al/KCl system, as well as in the pure KCl crystal, is studied as a function of isochronal annealing. For low temperatures up to 200°C we observe enhanced diffusion of Bi in all systems. At higher temperatures (up to 500°C) a regular diffusion governs the depth profiles.