Function Of Cu Research Articles

The effect of oxygen on the properties of transparent conducting Cu–Al–O thin films deposited by rf magnetron sputtering

Cu–Al–O thin films were prepared by rf magnetron sputtering. By adjusting oxygen partial pressure, the effect of oxygen on optical transmission and electrical properties of the films were investigated. The films exhibit good transparency in the visible range. As oxygen partial pressure is above 30%, the transmittance is about 60–70%. The direct and indirect band gaps are about 3.49 and 1.86 eV, respectively. The linear I– V relations exhibit ohmic contacts between Ag and the films, which suggest that the work function of Cu–Al–O thin films is around 4.26 eV. In the temperature range of 250–310 K, the temperature dependence of the conductivity of Cu–Al–O thin films is of semiconducting thermal-activation type. The average conductivity at room temperature successively increases as the oxygen partial pressure augments. The maximum conductivity is 4.6 × 10 −3 S cm −1 for Cu–Al–O thin film deposited at 40% oxygen partial pressure. When above 40%, the decrease of the conductivity may be due to the inhibition of the carrier transport led by the semiconductor trap states originated from the excess oxygen atoms.

An EPR study of Cu 2+ ions in [Zn(picol) 2(H 2O) 2]·2H 2O single crystals

Electron paramagnetic resonance spectra of Cu 2+-doped [Zn(picol) 2(H 2O) 2]·2H 2O (C 12H 18N 2O 8Zn) single crystals which were taken at room temperature are discussed. It was found from the analysis of the EPR data that the Cu 2+ ions substitute for magnetically inequivalent Zn 2+ ions. Two magnetically inequivalent sites for Cu 2+ were observed. The spin Hamiltonian parameters were determined and thus, the ground state wave functions of Cu 2+ ions in two sites were constructed.

EPR spectra of Cu 2+ doped [Zn(sac) 2(dmen)] and [Zn(sac) 2(paen)] single crystals

Cu 2+ doped single crystals of [Zn(sac) 2(dmen)] (sac: saccharinate, dmen: N, N′-dimethylethylendiamine) and [Zn(sac) 2(paen)], (paen: N, N′-bis(3-propylamine)ethylendiamine) complexes have been investigated by electron paramagnetic resonance (EPR) technique. Detailed investigations of the EPR spectra indicate that Cu 2+ ion substitute with Zn 2+ ion and forms tetrahedral complex in [Zn(sac) 2(dmen)] and octahedral complex in [Zn(sac) 2(paen)] hosts. Principal values of the g and hyperfine tensors are determined and the ground state wave functions of Cu 2+ ions are obtained using EPR parameters.

Dielectric function of Cu, Ag, and Au obtained from reflection electron energy loss spectra, optical measurements, and density functional theory

Pairs of reflection electron energy loss spectra recorded at different incident energies are decomposed to give the energy loss distribution in individual inelastic collisions at the surface and in the bulk of the solid. The resulting single scattering loss distributions are fitted to a Drude-Lindhard model for the dielectric function in the spectral range between the near visible and soft x-ray regions. Good agreement is found between the retrieved optical constants, density functional theory calculations, and optical measurements, rendering this type of analysis promising for the investigation of surface plasmons and determination of optical constants of individual nanostructures.

ESR and optical study of Cu 2+-doped Bis( l-asparaginato)zinc(II)

The Electron spin resonance (ESR) study of Cu 2+-doped Bis( l-asparaginato)zinc(II) has been done at room temperature. Two magnetically equivalent sites for Cu 2+ have been observed. The spin-Hamiltonian parameters evaluated with the fitting of spectra to rhombic symmetry crystalline field are g x = 2.0341 ± 0.0002 , g y = 2.0649 ± 0.0002 , g z = 2.2390 ± 0.0002 , A x =(51±2)×10 −4 cm −1, A y =(75±2)×10 −4 cm −1and A z =(169±2)×10 −4 cm −1. The ground state wave function of Cu 2+ has also been determined. The g-anisotropy has been estimated and compared with the experimental value. Further with the help of optical study, the nature of bonding of metal ion with different ligands in the complex has been discussed.

ESR and optical study of Cu 2+ doped calcium malonate dihydrate

The ESR study of Cu 2+ doped calcium malonate dihydrate has been done at room temperature. Four magnetically in-equivalent sites for Cu 2+ have been observed. The spin-Hamiltonian parameters evaluated with the fitting of spectra to rhombic symmetry crystalline field are for Cu 2+ site (I): g x = 2.0963 ± 0.0002, g y = 2.1316 ± 0.0002, g z = 2.4137 ± 0.0002, A x = (32 ± 2) × 10 −4 cm −1, A y = (34 ± 2) × 10 −4 cm −1, A z = (49 ± 2) × 10 −4 cm −1, for site (II): g x = 2.0668 ± 0.0002, g y = 2.0800 ± 0.0002, g z = 2.3561 ± 0.0002, A x = (34 ± 2) × 10 −4 cm −1, A y = (36 ± 2) × 10 −4 cm −1, A z = (51 ± 2) × 10 −4 cm −1, for site (III): g x = 2.0438 ± 0.0002, g y = 2.0623 ± 0.0002, g z = 2.2821 ± 0.0002, A x = (34 ± 2) × 10 −4 cm −1, A y = (36 ± 2) × 10 −4 cm −1, A z = (53 ± 2) × 10 −4 cm −1, and for site (IV): g x = 2.0063 ± 0.0002, g y = 2.0241 ± 0.0002, g z = 2.2357 ± 0.0002, A x = (35 ± 2) × 10 −4 cm −1, A y = (37 ± 2) × 10 −4 cm −1, A z = (54 ± 2) × 10 −4 cm −1. The ground state wave function of Cu 2+ has also been determined. The g-anisotropy has been estimated and compared with the experimental value. Further with the help of optical study the nature of bonding of metal ion with different ligands in the complex has been discussed.

Substituent Effect on Proton Affinity of Imidazole in Cu,Zn‐Superoxide Dismutase

AbstractTo investigate whether the proton‐accepting ability of imidazole in Cu,Zn‐superoxide dismutase (SOD) was possibly modulated by Zn(II) or not, the proton affinity (Ap) of N3 in imidazole group was calculated by density functional theory (DFT) with B3LYP functional. It was found that Zn(II) attenuates the Ap, because of its electron‐withdrawing effect, while the three ligands connected with Zn(II) (residues of two His and one Asp) exert an opposite effect, owing to their electron‐donating ability. This finding suggested that the three ligands should play a role in the normal function of Cu,Zn‐SOD and should be taken into consideration in the future study.

PEEM study of work function changes in Cu, Au and Pd metal surfaces with surface acoustic wave propagation

The effects of surface acoustic wave (SAW) on the work function of Cu, Au and Pd metal surfaces with different surface structures were studied by photoelectron emission microscopy (PEEM). SAW propagation produced bright PEEM images for Cu, Au and Pd metal surfaces consisting of high-index planes and step sites, whereas it yielded dark images for the metals exposing low-index planes, indicating that the SAW enhanced photoemission from rough metal surfaces containing coordinatively-unsaturated metal atoms and lowered that from densely packed smooth metal surfaces. Changes in the PEEM images with SAW-on and SAW-off were reversible and were associated with decreases and increases in the work function of the metal surfaces, respectively. The SAW caused periodic and vertical lattice displacement, and it was demonstrated that large lattice displacement was responsible for work function changes from coincidence between the patterns of photoemission and lattice displacement. A mechanism for work function changes is proposed on the basis of effects on the spatial structures and electronic properties of metal surfaces.

Copper cofactor delivery in plant cells

Copper (Cu) is a micronutrient that has roles in photosynthesis, respiration, antioxidant activity, cell wall metabolism and hormone perception. Excess Cu is toxic and therefore its delivery has to be tightly regulated. Recent progress in the study of Cu homeostasis has revealed not only components of the Cu delivery machinery but also regulatory systems that control Cu-protein expression and coordinate the activity of Cu-delivery systems. The response of photosynthetic organisms to Cu deficiency indicates the existence of cross-talk between metal cofactor delivery pathways. Next to its well-established roles in plant metabolism, a novel function for Cu, first discovered in plants, is in the biogenesis of molybdenum cofactor. Defects in Cu delivery factors also suggest important roles for Cu in cell expansion.

New findings on protein expression in copper deficient rat heart using proteomic approaches

Dietary Cu-deficiency not only causes a hypertrophic cardiomyopathy but also increases cancer risk in rodent models. The present studies were undertaken to determine the effect of Cu-deficiency on protein profiles in rat heart tissue. Male Sprague-Dawley rats were fed diets that were either copper adequate (6.0 μg copper/g diet n = 6) or copper deficient (0.3 μg copper/g diet n = 6) for 5 wk. An approach using liquid chromatography mass spectrometry analysis coupled with DNA gel shift and immunodection dot blotting revealed a 132 kDa protein complex in the protein extract from hearts of Cu-deficient, but not Cu-adequate rats. This complex contained a collagen alpha (I) chain precursor as well as a leucine-rich protein 130 (DNA binding protein). These data suggest that Cu-deficiency may have a potential to influence DNA stability and mRNA transcript processing. Another approach to determine the effect of Cu deficiency on protein profiles used the combination of the isotope-coded affinity tag (ICAT) method and Western blotting analysis. ICAT analysis suggested that protein profiles from heart tissue of Cu-deficient rats were different from those of Cu-adequate rats; seven major protein species differed by more than a 100% increase or a 50% decrease. Western blotting analysis confirmed an 85% increase in fibulin-5 (also known DANCE/EVEC) in Cu-deficient rat heart, and suggested a critical biological function of Cu in controlling vascular redox state, scaffolding of cells to elastic fiber, and preventing elastinopathy in the rat heart.

EPR Spectral Simulation for Silk Fibroin-Cu(II) Complexes with Multiple Components

The simulation for electronic paramagnetic resonance (EPR) spectrum with hyperfine couplings as well as multiple coordination components is often difficult. Here we develop a simulation approach based on the second-order perturbation theory to address these issues. The EPR spectral simulations of the silk fibroin-Cu(Ⅱ) complexes are taken as examples to illustrate this approach, efficiently revealing the function of Cu(Ⅱ) in the spinning process of silkworm. In addition, this approach would be useful for the EPR simulations of complexes containing Fe(Ⅱ), Mn(Ⅱ), V(Ⅲ) and other paramagnetic ions.

X-ray crystal structure and Cu 2+ doped EPR studies of tetraaquabis(isonicotinamide)zinc(II) and -cobalt(II) disaccharinate 1.5 hydrate single crystals

Crystal structure of [M(ina) 2(H 2O) 4](sac) 21.5H 2O (M=Zn 2+( 1), Co 2+( 2); ina for isonicotinamide or pyridine-4-carboxyamide and sac for saccharine) complexes have been determined by X-ray diffraction analyses and their magnetic environments have been identified by electron paramagnetic resonance (EPR). The isostructural complexes of 1 and 2 both crystallize in the monoclinic system. In both complexes, the octahedral metal atom, which rides on a crystallographic center of symmetry, is coordinated by two monodentate isonicotinamide ligands through the ring nitrogens and four aqua ligands to form a discrete [M(ina) 2(H 2O) 4] 2+ unit, which captures up and down two saccharinate ions, each through intermolecular hydrogen bonds. The EPR analyses of Cu 2+ doped 1 and 2 single crystals indicate that there is one magnetic centre with two magnetically inequivalent sites for the paramagnetic Cu 2+ ion in 1, whereas two magnetic centres with each having two magnetically inequivalent sites are observed in 2. The spin Hamiltonian parameters together with the molecular orbital coefficients for each crystal of 1 and 2 were derived from the EPR spectra and these were used to construct the ground state wave function of Cu 2+ ion in each crystal.

Linking biosensor responses to Cd, Cu and Zn partitioning in soils

Soils bind heavy metals according to fundamental physico-chemical parameters. Bioassays, using bacterial biosensors, were performed in pore waters extracted from 19 contrasting soils individually amended with Cd, Cu and Zn concentrations related to the EU Sewage Sludge Directive. The biosensors were responsive to pore waters extracted from Zn amended soils but less so to those of Cu and showed no toxicity to pore water Cd at these environmentally relevant amended concentrations. Across the range of soils, the solid-solution heavy metal partitioning coefficient ( K d) decreased ( p < 0.01) with increasing amendments of Cu and Zn; Cu exhibited the highest K d values. Gompertz functions of Cu and Zn, K d values against luminescence explained the relationship between heavy metals and biosensors. Consequently, biosensors provide a link between biologically defined hazard assessments of metals and standard soil-metal physico-chemical parameters for determining critical metal loadings in soils.

Substrate temperature dependence on the optical properties of Cu and Ag thin films

Copper (260 nm) and Ag (1000 nm) films deposited on glass substrates, at different substrate temperatures. Their optical properties were measured by ellipsometry (single wavelength of 589.3 nm) and spectrophotometry in the spectral range of 200–2600 nm. Kramers Kronig method was used for the analysis of the reflectivity curves of Cu and Ag films to obtain the optical constants of the films, while ellipsometry measurements was carried out as an independent method. The influence of substrate temperature on the microstructure of thin metallic films [Structure Zone Model (SZM)] is well established [Movchan and Demchishin, Phys. Met. Metall. 28, 83 (1969); Thornton, J. Vac. Sci. Technol. 12, 830 (1975); Savaloni and Bagheri Najmi, Vacuum 66, 49 (2002); Savaloni and Player, Vacuum 46, 167 (1995); Savaloni et al., Vacuum 43, 965 (1992)]. The Effective Medium Approximation (EMA) analysis was used to establish the relationship between the SZM and EMA predictions. Good agreements between SZM as a function of substrate temperature and the values of volume fraction of voids obtained from EMA analysis, is achieved; by increasing the substrate temperature the separation of the metallic grains decreases, hence, the volume fraction of voids decreases and denser films formed. The predictions of the Drude free-electron theory are compared with experimental results for dielectric functions of Cu and Ag films of different substrate temperature. The real part of the dielectric constant is decreased with increasing the substrate temperature, while the imaginary part of the dielectric constant increased with temperature for both materials over the whole energy range measured, including intraband and interband regions. The increase of the imaginary part in the interband region suggests a temperature and frequency dependence of the relaxation time in the Drude model, namely

ESR of copper-doped sodium citrate

Single crystal ESR spectra of Cu 2 + ion doped in sodium citrate are reported at room temperature. The observed spectra are fitted to a spin-Hamiltonian of rhombic symmetry with g x = 2.1076 ± 0.002 , g y = 2.1289 ± 0.002 , g z = 2.4454 ± 0.002 , A x = ( 40 ± 2 ) 10 - 4 cm - 1 , A y = ( 62 ± 2 ) 10 - 4 cm - 1 and A z = ( 78 ± 2 ) 10 - 4 cm - 1 . It is found that Cu 2 + enters the lattice as a substitutional impurity replacing an Na + ion. The ground state wave function of Cu 2 + ion in this lattice is also determined from the spin-Hamiltonian constants obtained from ESR results. It is found that the ground state is predominantly | x 2 - y 2 〉 . With the help of the optical absorption study, the nature of bonding in the complex has also been discussed.

EPR studies of Cu2+-doped bis(saccharinato)bis(pyridine)zinc(II) single crystals

The electron paramagnetic resonance spectra of Cu 2+ impurities in bis(saccharinato)bis(pyridine)zinc(II) single crystals have been studied at room temperature in three mutually perpendicular planes. The angular variation of the spectra indicates the substitution of the host Zn 2+ with Cu 2+ . Two magnetically inequivalent sites for Cu 2+ have been observed. The spectra were fitted to the rhombic spin Hamiltonian. The spin Hamiltonian parameters and the molecular orbital coefficients were evaluated for the two sites. The ground-state wave function of Cu 2+ ion in the lattice has been constructed.

Single crystal EPR and optical absorption studies of Cu 2+ ion in l-arginine sulphophosphate monohydrate—a nonlinear optical crystal

The EPR spectra of Cu 2+ ion in l-arginine sulphophosphate monohydrate (LASP), a nonlinear optical material (NLO) have been studied at room temperature. Two magnetically inequivalent interstitial Cu 2+ sites in the lattice were identified. The principal values of g- and A-tensors indicate that the symmetry of the electrostatic field around the Cu 2+ ion is rhombic. Bonding parameters have been evaluated and the ground state wave function of Cu 2+ ion is constructed. The ground state is found to be an admixure of | x 2 − y 2 〉 and | 3 z 2 − r 2 〉 orbitals. By correlating EPR and optical absorption spectra the crystal field parameters have been evaluated.

Continuity and morphology of TaN barriers deposited by Atomic Layer Deposition and comparison with physical vapor deposition

“Continuity and Morphology of TaN barriers deposited by Atomic Layer Deposition and Comparison with Physical Vapor Deposition”: After barrier deposition the samples were exposed to a HF solution at various concentrations and various exposure times and analyzed by cross-sectional Scanning Electron Microscopy analysis in order to reveal any discontinuities in the barrier films. A comparison has been made between SIP and SIP EnCoRe ionised Physical Vapour Deposition (PVD) and two ALD approaches: ALD only and ALD-etch-ALD. The ALD barrier does not show evidence of pinholes after being subjected to the etching test. The results from this etching test indicate that a 20 cycle ALD TaN barrier deposited on oxide is continuous and free from pinholes. The SIP EnCoRe barrier outperforms the SIP barrier with respect to Barrier continuity. The step coverage and conformality of the ALD and PVD films were measured with Transmission Electron Microscopy on the same high aspect ratio structures. The study was extended by a top view SEM CD analysis to measure the overhang of barrier and seed film as function of Cu seed bias and underlying barrier. It is shown that a larger process window for the Cu seed deposition exists if the barrier thickness is reduced.

Copper(II) selective electrochemical sensor based on Schiff Base complexes

Plasticized membranes using Schiff Base complexes, derived from 2,3-diaminopyridine and o-vanilin have been prepared and explored as Cu 2+-selective sensors. Effect of various plasticizers viz., dibutyl phthalate (DBP), dioctylphthalate (DOP), chloronaphthalene (CN), tri- n-butylphosphate (TBP) etc. and anion excluder, sodium tetraphenylborate (NaTPB) was studied in detail and improved performance was observed at several instances. Optimum performance was observed with Schiff Base (B) having a membrane composition of B(1%):PVC(33%):DOP(65%):NaTPB(1%). The sensor works satisfactorily in the concentration range 5.0×10 −6 to 1.0×10 −1 M (detection limit 0.3 ppm) with a Nernstian slope of 29.6 mV per decade of activity. Wide pH range (1.9–5.2), fast response time (<30 s), high non-aqueous tolerance (up to 20%) and adequate shelf life (>4 months) indicate the vital utility of the proposed sensor. The potentiometric selectivity coefficient values as determined by match potential method (MPM) indicate good response for Cu 2+ in presence of interfering ions. The tolerance level of Hg 2+, which causes serious interference in the determination of Cu 2+ ions ( K Cu 2+Hg 2+ Pot(MPM): 0.45), was determined as a function of Cu 2+ concentration in simulated mixtures. The sensor was also used in the potentiometric titration of Cu 2+ with EDTA.

Interface Fermi level pinning in a Cu/p-CuGaS 2 Schottky diode

A Schottky contact to p-type CuGaS 2 that showed the highest rectification ratio of approximately 500 ever reported was realized using a Cu electrode on a HF/HNO 3-treated surface, as well as an excellent Au ohmic contact on a HF-etched surface. The effective Schottky barrier height of 0.9 eV was obtained from the current–voltage and capacitance–voltage characteristics. The value was smaller by 1.1 eV than that calculated from the values of the work function of Cu and electron affinity of CuGaS 2. The results indicated a surface pinning of the Fermi level to certain acceptor-type gap states below the midgap.