Region Of Cu Research Articles

Formation of poly(methylmethacrylate) layers on the surface and intergallery regions of Cu 2+-, Fe 3+-, and VO 2+-exchanged hectorite thin films

We have used the techniques of scanning force microscopy (SFM), electron spin resonance (ESR) spectroscopy, ATR IR spectrometry, and powder X-ray diffraction (XRD) to investigate the reaction of methylmethacrylate (MMA) on metal cation-exchanged hectorite thin films. SFM images of the topmost surface of Cu 2+-, VO 2+-, and Fe 3+-exchanged hectorite exposed to liquid MMA show that in all three cases a complete layer of the polymer, polymethylmethacrylate (PMMA), has formed. IR spectra taken on the same films support the SFM observations for the VO 2+ and Fe 3+ samples, but are not conclusive for the Cu 2+-exchanged films. The PMMA formed on the surface of these films is segregated into small grains or bundles, ranging in average size from 250 Å (Cu 2+ hectorite substrate) to several thousand ångström units (Fe 3+ hectorite substrate). XRD and ESR measurements on these thin films indicate that little intercalation of the MMA monomer into the intergallery regions of the Cu 2+-exchanged clay film occurs. This result is substantiated by SFM phase-contrast images of exposed intergallery regions in these samples. For the VO 2+- and Fe 3+-exchanged hectorite films, XRD-measured basal spacings show moderate intercalation of the organic monomer. SFM images of these intergallery regions clearly indicate the presence of interlayer polymer, in the form of quasi-two-dimensional sheets.

タングステンと銅との摩擦圧接性に及ぼすNbインサート材の厚さの影響

The bond strength and microstructure of a Cu (copper)/W (tungsten) joint friction-welded with an intermediate layer of Nb (niobium) foil 7-25 μm thick have been investigated in order to find proper thickness of the intermediate layer for obtaining a joint with high performances and slight microstructural changes in the weld. The tensile strength of the joint was increased more rapidly with the friction time, as the thickness of the intermediate layer was decreased. For all the joint obtained in this investigation, a number of Nb particles were incorporated into the Cu adjacent to the weld interface, forming a mixed region of Cu and Nb. The width of this mixed region and the number density of the involved Nb particle were decreased, as the intermediate layer thickness was decreased. In this mixed region and at the weld interface, significant amounts of porosities and uncontacted areas were observed at friction times shorter than 2 s, when the intermediate layer thickness was more than 15 μm. From these results, it can be concluded that in the Nb foil employed in this investigation thinner one is more favorable as an intermediate layer for the friction welding of copper to tungsten. The effect of the intermediate layer on the bond strength is also discussed considering the interaction of the Nb particle with W and O during the friction welding.

Hexachlorocuprate(II) Anion: Vibration Spectra and Structure

For the complexes (CH8N4)2[CuCl6], (C2H9N5)2[CuCl6] · 2H2O, and (CH8N4O)4[CuCl6]Cl4, where (CH8N4)2+, (C2H9N5)2+, and (CH8N4O)2+ are the aminoguanidinium, biguanidium, and carbohydrazidium cations, respectively, IR and Raman spectra were taken and analyzed in the region of Cu—Cl vibrations. Polarization measurements of the Raman spectra of (CH8N4O)4[CuCl6]Cl4 single crystals were performed with the purpose of assigning the vibrations to symmetry types. Vibration spectra were calculated for the hexachlorocuprate ion in the given series of compounds, and the spectra of the examined complexes were compared with spectra of the previously known compounds incorporating the hexachlorocuprate(II) ion.

Protective Properties of Dodecanethiol Layers on Copper Surfaces: The Effect of Chloride Anions in Aqueous Environments

The protective properties of dodecanethiol layers against copper corrosion in a Borax buffer containing chloride anions are investigated by using electrochemical techniques complemented with scanning tunneling microscopy. Results show that copper is protected against corrosion provided that the copper electrode does not reach the potential region of Cu(II) oxide formation and the concentration of chloride ions in the environment remains low. These findings should be taken into account for the use of alkanethiol layers for the corrosion protection of copper.

Device Analysis of Cu(In,Ga)Se2Heterojunction Solar Cells - Some Open Questions

ABSTRACTThe paper discusses the electronic properties of Cu(In,Ga)Se2–based heterojunction solar cells with a special focus on questions which at present are not satisfactorily understood. First, we discuss an apparent quantitative contradiction between measured concentrations of recombination centers in the Cu(In,Ga)Se2absorber material and the actual recombination rate in the solar cells. We propose, as a possible explanation for that observation, that the defect concentration in Cu(In,Ga)Se2is spatially inhomogeneous with a systematic increase towards the heterojunction interface. Second, we address the issue of electronic metastabilities in ZnO/CdS/Cu(In,Ga)Se2heterojunctions and, especially, in devices that use alternative buffer materials instead of CdS. Starting from a brief review of the experimentally observed types of metastabilities, we demonstrate by thermally stimulated capacitance measurements that a specific type of metastability that severely limits the performance of solar cells with non-CdS buffers is present also in high-efficiency standard devices though it has virtually no influence on the output parameters in the latter case. A possible explanation of this type of metastability points to a metastable defect reaction localized in the close to surface region of Cu(In,Ga)Se2. At the moment we cannot propose conclusive models for both open questions. However, we can localize the answers to both problems in the close-to-surface region of the Cu(In,Ga)Se2absorber.

Bound hole states and ferrons in HTSC

Bound hole states induced by excess oxygen in La 2CuO 4+ δ and YBa 2Cu 3O 6+ x are studied in the framework of the extended Hubbard model with the use of the spin-wave approximation and the Lanczos algorithm. We interpret the band at 0.5 eV in the impurity reflectivity spectrum of La 2CuO 4+ δ as a manifestation of the transition from the lowest bound hole level (S z= 1 2 ) to band states. It is shown that for realistic parameters an excess O 2− ion does not lead to the formation of a ferromagnetically ordered region of Cu spins around a localized hole (ferron). On the other hand, a spin-carrying O − defect in Cu–O chains of YBa 2Cu 3O 6+ x does generate such excitation at small hole concentrations.

The Effect of Quench Rate on the Microstructure and Properties of AF/C-458 and AF/C-489 Al-Li-Cu-X Alloys

The Air Force recently developed two isotropic Al-Li-Cu-X alloys with 1.8W/oLi and 2.1w/oLi designated AF/C-458 and AF/C-489, respectively. The objective of this investigation was to determine the effect of quench rate on the microstructure and mechanical properties of the AF/C-458 and AF/C-489 alloys. TEM, SEM, microhardness, and tensile testing were utilized to ascertain these microstructure/property relationships for both alloys in the T4, T6, and T86 tempers as a function of quench rate. Subsequent losses in ductility for both alloys in all tempers with decreasing quench rate were determined to be due to the precipitation of the equilibrium Al 2 CuLi (T 1 ) phase along subgrain and grain boundaries which promoted intergranular fracture. Furthermore, yield and tensile strengths increased for both alloys in the T4 temper but decreased in the T6 and T86 tempers with decreasing quench rate. The increased strengths for the T4 condition resulted from the heterogeneous precipitation of coarse T 1 and naturally aged δ' phases. The decrease in yield and tensile strengths for the T6 and T86 tempers were also due to the coarse heterogeneous precipitation of T 1 which denuded regions of Cu thereby reducing the number density of fine matrix θ (T6) and T, (T86). Finally, a comparison of the quench sensitivity for both the AF/C-458 and AF/C-489 alloys indicates that the mechanical properties for both alloys were less quench rate sensitive than other typical Al-Li-Cu-X alloys.

The formation of poly(methyl-methacrylate) on transition metal-exchanged hectorite

Hectorite clay films exchanged with Cu 2+ or Fe 3+ react with methyl-methacrylate monomer in a solventless process to form poly(methyl-methacrylate) (PMMA). Scanning force microscopy (SFM), electron spin resonance (ESR), and X-ray diffraction (XRD) are useful in studying the resulting clay/polymer composite. SFM shows that PMMA forms on the surface of both the Cu 2+- and Fe 3+-exchanged films. In addition, XRD shows PMMA formation in the interlayer region of the Fe 3+-exchanged hectorite but not the interlayer region of Cu 2+-exchanged hectorite. SFM shows that the morphology of the polymer formed on the film surface depends on: (1) the type of transition metal exchanged into the interlayer region. (2) The mode of delivery (vapor vs. liquid) of methyl-methacrylate monomer to the surface of the clay. PMMA does not form to a significant extent on or within Ca 2+-exchanged hectorite, and ESR shows no evidence of free radical formation or reduction of the transition metals during any of the polymerization reactions. The results suggest the possibility of an unusual cationic polymerization of methyl-methacrylate to form PMMA with organic cations being stabilized by interaction with the silicate surface. The experimental results have implications for “solventless synthesis” of PMMA and other polymers.

Ionic and electronic conductions in liquid metal–chalcogen systems

The measurements of electronic and ionic conductions in liquid In–Se and Cu–Se systems have been carried out separately as a function of concentration and temperature. The electronic conductivities of these systems have minima near the composition x=0.58 for the In 1− x Se x system and x=0.33 for the Cu 1− x Se x system. Both systems have maxima in the ionic conductivities at the same composition. In proportion as the electronic conductivity increases with changing composition, the ionic conductivity decreases. In Se-rich region of Cu–Se system, the change from negative to positive temperature dependence of the electronic conductivity and a discontinuous change in the ionic conductivity have been observed at a certain temperature.

Light-Induced Metastabilities in the Interface Region of Cu(In,Ga) Se<sub>2</sub>-Based Photovoltaic Devices Studied by Laplace Transform Junction Spectroscopy

Light-Induced Metastabilities in the Interface Region of Cu(In,Ga) Se<sub>2</sub>-Based Photovoltaic Devices Studied by Laplace Transform Junction Spectroscopy

Slow positron annihilation studies of vacancy-type defects in the near-surface region of Cu and Nb before and after wear

The distribution of the vacancy-type defects in the near-surface region of single-crystalline Cu and Nb before and after wear was investigated by slow positron annihilation. It was found that a lot of vacancy-type defects were produced by wear in Cu samples. For Nb, the S parameters in the area from the surface to the depth of 160 nm after wear were smaller than both those in the same area before wear and those in the area beyond 320 nm after wear, which was possibly due to the resulting compounds, new phases, or different types of defects in the very near surface region. In the depth beyond 320 nm, the S parameter profile of Nb after wear shows that in this area a lot of vacancy-type defects were produced by wear.

Comparative study of the L23–M45M45 Auger decay in CuO and Cu using synchrotron radiation

Abstract We report on the evolution of L 3 – and L 2 – M 45 M 45 Auger spectral regions in Cu and CuO as a function of photon energy used to create the initial hole states. It is shown that the satellite features in Auger spectra are completely suppressed close to the threshold; intensities of these satellites increase dramatically when photon energy is swept through deeper core level thresholds. We discuss various decay channels responsible for the spectral features in the L 23 – M 45 M 45 regions of Cu and CuO and obtain quantitative estimates for their contributions to the total spectrum.

Cu + Au alloy particles formed in the underpotential deposition region of copper in acid solutions

Cu + Au alloy particles electrodeposited on an amorphous carbon electrode at the underpotential region of Cu in both perchloric acid and sulfuric acid solutions were investigated by means of transmission electron microscopy. The fraction of Cu in the Cu + Au alloy particles grown in both acid solutions with a concentration of 1 mM Au ion increased while the underpotential deposition (UPD) potential was decreased. However, it was independent of the concentration of Cu ion in solution. It is inferred that the composition of the Cu + Au alloy particles is dependent on the UPD potential. The fraction of Cu in the Cu + Au alloy particles grown at around the reversible Nernst potential of Cu in 0.1 mM HAuCl4 + 50 mM Cu(ClO4)2 containing perchloric acid solution was 505. This result suggests a layer-by-layer formation of the Cu + Au alloy particles. The fraction of Cu in the Cu + Au alloy particles formed in the presence of sulfate was lower than that in the perchloric acid solution as the UPD potential and the concentration of Cu ion were the same. This is attributed to an influence of coadsorbed sulfate ions.

Decahedral and icosahedral Cu-Au alloy particles grown under a controlled-potential region in acid solutions

Decahedral and icosahedral Cu-Au alloy particles have been formed by electrochemical deposition of Cu and Au in perchloric acid and sulfuric acid solutions at electrode potentials where formation of decahedron and icosahedron Au particles has not been previously observed. This observation is thought to occur due to a contraction of the Au overlayer, induced by the presence of an incompletely discharged ${\mathrm{Cu}}^{+}$ ion deposited on the Au overlayer of the alloy particles in the underpotential deposition region of Cu. This phenomenon is therefore analogous to the alkali-metal-induced reconstruction of Au surfaces. However, decahedral and icosahedral Cu-Au alloy particles were not observed in the Cu-Au alloy particles when the Cu content of the alloy exceeded 30%. It is known that the topmost layer of the reconstructed Au(111) surface is contracted by about 4% and that the lattice spacing of the Cu-Au alloy containing 30% Cu is shortened by about 3% with respect to the Au bulk lattice. Therefore, the lattice mismatch between the Au overlayer and the substrate of Cu-Au alloy particles containing more than 30% Cu is small enough so that no decahedral and icosahedral particles are formed.

Distinct Regions of Cu(I)·ACE1 Contact Two Spatially Resolved DNA Major Groove Sites

The interaction between the Cu(I).ACE1 (CuACE1) transcription factor and its DNA binding site in the yeast metallothionein gene was studied by systematically altering the DNA sequence through base substitution, modification, and deletions as well as by altering the protein structure through chemical modification. We show here that CuACE1 is comprised of two distinct domains that contact DNA through minor groove interactions located between two major groove interaction sites. The minor groove interactions are shown to be critical for formation of a stable CuACE1.DNA complex. The NH2-terminal segment of ACE1 is shown to contact the 5'-most distal major groove site.

Studies on CuIn precursor for the preparation of CuInSe2 thin films by the selenization technique

Abstract The effect of temperature on the degree of alloy formation between Cu and In layers has been studied for the preparation of CuInSe 2 films by the selenization technique. The mechanism of alloy formation is different in bilayers annealed at temperatures lower and higher than the melting point of In, or prepared by deposition of Cu and In at 200°C and 150°C, respectively. While the annealing of the precursor up to 200°C produces an alloy in the interface region of Cu and In layers, annealing at 500°C completely changes its morphology. The effect of alloy formation in the precursor on the selenized CuInSe 2 films is studied using structural, morphological, optical and compositional properties.

Lattice vibration effects on electronic structure and photoemission

A theoretical approach to the electronic structure of solids at finite temperature has been developed on the basis of the adiabatic approximation. For any given temperature, correlated ion core displacement configurations on a large cluster are determined, which are consistent with experimental phonon dispersion relations. The electron Bloch spectral function, i.e. a generalized band structure, and photoemission intensities are obtained by a tight-binding recursion method for each configuration followed by a configurational average. Calculations for the 3 d-band region of Cu yield the vibration-induced hole lifetime broadening (typically about 0.35 eV at 900 K) and real energy shifts (up to ±0.1 eV). Due to a compensation by thermal lattice dilation, the d-band width changes only marginally with T. Comparison with experimental photoemission data from Cu(1 1 0) shows good agreement for the temperature dependence of peak height, line shape and energy shift.

Thermal behaviour of Cu(II)-urea complex

The urea complex of copper was synthesized and its structure was established by Fourier transform infrared (FTIR), electron spin resonance (ESR) and atomic absorption spectroscopy and elemental analysis to be Cu(urea)4Cl2. The thermal behaviour of this complex has been studied by thermogravimetry and differential thermal analysis and FTIR and ESR. Thermal analysis shows that the decomposition of the complex occurs in four stages of weight loss of different intermediates followed by three endothermal effects. The complex is thermally stable up to 428 K. The ESR and FTIR behaviour of the Cu(II)-urea complex during thermolysis was studied between 428 and 633 K. The experimental results suggest that in this temperature range the complex decomposition occurred forming thermodynamically stable regions of Cu(II) which are ferromagnetically coupled.

Superconducting proximity effect in Cu clad Nb wires doped with Mn, Fe, Co and Ni

Abstract The Meissner effect in Cu doped with Mn, Fe, Co and Ni which is induced by the proximity effect of Nb is measured. The thickness ϱ of the Meissner region in Cu is found to be a linear function of T −1 2 except for Mn-impurity sample. The ϱ of Mn-impurity sample is suppressed by the magnetic scattering around T K and recovered with decreasing temperature below T K . This result indicates that the pair breaking probability due to Mn impurities rapidly decreases below T K . The dc magnetic field dependence of ϱ shows anomalous behavior around T K .

Space-charge-limited-current diode model for CuxS/CdS solar cells and their degradation

A space-charge-limited-current diode model for CuxS/CdS solar cells accurately models their current-density-versus-voltage (J-V) curves for a 9.2% efficient device and a 4.1% efficient device that degraded to 0.3% efficiency in hot-moist air. For a 1-μm-thick, high-resistance region of Cu compensated CdS at the interface to the CuxS, all the measured fill factors from 0.54 to 0.71 and the open-circuit voltages from 0.41 to 0.52 V are well fit for steady-state conduction electron concentrations between 1.2×109 and 6.9×1010 cm−3 and for electron trap densities between 7×1014 and 5×1018 cm−3 eV−1 at energies of 0.3–0.5 eV below the conduction-band edge of this high-resistance CdS region. The trap changes that occur with short-circuit current degradation increase the fill factor. A CuxS/CdS configuration is proposed to reduce reproducibility problems and to eliminate all the known modes of degradation with the possible exception of photoinduced degradation. Efficiency increases of 10%–11% are projected.