Observation Of Cu Research Articles

SUPERCONDUCTIVITY AND CuK-XANES OF (Hg, Re)Sr2CuO4+δ

The 1201-type nominal ( Hg 0.9 Re 0.1) Sr 2 CuO 4+δ samples, synthesized at ~920°C in partial vacuum, show, from temperature dependent dc-magnetization, [Formula: see text]. The CuK-edge features obtained from X-ray absorption measurements on the sample show predominantly Cu 2+ state and a weak but distinct Cu 1+ signature due to superconducting 1201 phase (after taking due account of impurity Sr 2 CuO 3, and SrCuO 2 phases). The presence of Cu 1+ signature in SC samples is consistent with our earlier observations of Cu 1+ in Ba-free superconducting (Hg,Cr)-1201 and (Hg,Mo)-1201 materials.

Infrared spectra and density functional calculations of Cu(CO)1–4+, Cu(CO)1–3, and Cu(CO)1–3− in solid neon

Laser-ablated copper atoms, cations, and electrons react with CO molecules to give binary copper carbony neutral complexes as well as cation and anion complexes, which are isolated in solid neon and argon matrices. Based on isotopic substitution as well as density functional calculations of isotopic frequencies, absorptions at 2234.4, 2230.4, 2211.3, and 2202.1 cm−1 in neon are assigned to C–O stretching vibrations of the linear CuCO+ and Cu(CO)2+, trigonal planar Cu(CO)3+, and tetrahedral Cu(CO)4+ cations. The absorptions at 1746.2, 1793.9, and 1838.9 cm−1 in neon and at 1733.4, 1780.8, and 1829.7 cm−1 in argon are assigned to the linear CuCO− and Cu(CO)2−, and trigonal planar Cu(CO)3− anions, respectively. The solid neon observations of Cu(CO)1–3 are 20–9 cm−1 blue shifted from the argon matrix counterparts, which are in agreement with previous thermal copper atom matrix isolation studies. This work provides the first vibrational spectra of Cu(CO)1–4+ and Cu(CO)1–3−.

高耐食性非晶質膜の形成に関与する鋼板上のCu濃化層の観察

高耐食性非晶質膜の形成に関与する鋼板上のCu濃化層の観察

Volatile transport on Venus and implications for surface geochemistry and geology

The high vapor pressure of volatile metal halides and chalcogenides (e.g., of Cu, Zn, Sn, Pb, As, Sb, Bi) at typical Venus surface temperatures, coupled with the altitude‐dependent temperature gradient of ∼8.5 K km−1, is calculated to transport volatile metal vapors to the highlands of Venus, where condensation and accumulation will occur. The predicted geochemistry of volatile metals on Venus is supported by observations of Cu, Zn, Sn, Pb, As, Sb, and Bi minerals around terrestrial volcanic vents, spectroscopic observations of CuCl in volcanic gases at Kilauea and Nyiragongo, and large enrichments of these and other volatile elements in terrestrial volcanic aerosols. A one‐dimensional finite difference vapor transport model shows the diffusive migration of a thickness of 0.01 to >10 μm/yr of moderately to highly volatile phases (e.g., metal halides and chalcogenides) from the hot lowlands (740 K) to the cold highlands (660 K) on Venus. The diffusive transport of volatile phases on Venus may explain the observed low emissivity of the Venusian highlands, hazes at 6‐km altitude observed by two Pioneer Venus entry probes, and the Pioneer Venus entry probe anomalies at 12.5 km.

Observation of Cu 2+ electron spin resonance in Gd 2CuO 4

We report on low-temperature magnetic resonance magnetic measurements of Gd 2CuO 4 single crystals which belong to a family of electron-doped HTSC materials with general formula R 2− x Cu x CuO 4. Experiments are carried out using millimeter and far-infrared techniques combined with high magnetic fields. Three antiferromagnetic resonance branches with the following frequency gaps at 2 K: ω 1 = 0.8cm −1, ω 2 = 2.8cm −1, Ω 2 = 17cm −1 , are observed. The ω 1 and ω 2 frequencies correspond to Gd magnetic subsystem, the characteristic field and temperature dependence of Ω 2 resonance allow us to identify it as the Cu spin resonance.

STM observations of Cu(100)−c(2×2)N surfaces: evidence for attractive interactions and an incommensurate c(2 × 2) structure

STM studies of N on Cu (100), adsorbed via activated ion bombardment, reveal behaviour consistent with attractive interactions and an incommensurate c(2×2)N structure. For extremely low N doses, images of the resultant surface show roughly square shaped islands with island edges running along the 〈001〉 directions. The islands have an internal c(2 × 2) periodicity and while tending to group together do not coalesce. For higher N doses, island coalescence occurs simultaneously with the appearance of trench-like defect structures running in the 〈011〉) directions and small one-atomic layer high islands. Lack of island coalescence at low coverages and the appearance of trench-like defects at higher coverages are interpreted as strain-relief mechanisms for an incommensurate c(2×2)N structure. To derive the N adsorption site, S has also been coadsorbed along with the c(2×2)N islands to form coexisting p(2×2)S domains. The spatial relationships between features in both domains show that the protrusions observed in the c(2 × 2)N areas are located above four-fold hollow sites. Finally, in order to compare our work with previous studies, we have obtained detailed LEED I–V data from the various Cu(100)−c(2×2)N surfaces studied with STM.

Epr observation of Cu3+states in YBCO: Al single crystals

Abstract A new EPR spectrum in YBCO single crystals doped by Al ions has been assigned to trivalent Cu ions (S=1) in Cu(1) position and the spin-Hamiltonian parameters describing the observed spectrum have been determined. The analysis of the experimentally determined g-factor values showed the important role of the hybridization of 3d-copper and 2p-oxygen states and. in particular, the significant contribution of Cu2+ −O− state in the ground one. It was shown that the observed temperature dependence of S -value was due to the displacement of apex oxygen xO(4) in the direction of CuO2 plane as T→Tc.

EPR observation of Cu 2+Cu 2+ pairs in cupric oxide powders

We report the observation of an EPR spectrum attributable to Cu 2+Cu 2+ pairs with resultant electronic spin S = 1, from cupric oxide annealed in the temperature range from 700 to 900°C. The spectrum consists of only a single line at g = 3.12 with seven hyperfine components. From the weight loss and oxygen content measurements, it was found that the observation of such a signal strongly depends on the oxygen content of the sample.

An in Situ Transmission Electron Microscopy Study During NH3 Ambient Annealing of Cu-Cr Thin Films

ABSTRACTNitridation of Cu-Cr alloy films under an NH3 ambient was studied using in situ transmission electron Microscopy. Cu-Cr thin films (40–100 nm) were deposited on a single crystal NaCl substrate by electron beam coevaporation, and were heat treated up to 750°C at 2.5–3.0 Torr NH3. The films were also vacuum (10-6 Torr) annealed under the same conditions for comparison. Initial observation of Cu and Cr crystallization occurred at 470°C for both environmental conditions. The nitridation process of Cr to form CrN was observed initially at 580°C and was followed by evolution of faceted Cu grain growth in the CrN Matrix.

イオンスパッタによるコーン形成の１つの可能性 Ｃｕの動的観察

イオンスパッタによるコーン形成の１つの可能性 Ｃｕの動的観察

Monolayer and multilayer growth of Cu on the Ru(0001) surface

The adsorption and growth of Cu films on the Ru(0001) surface were studied by work function measurements, low-energy electron diffraction (LEED), Auger electron spectroscopy (AES) and thermal programmed desorption (TPD). The results indicate that for submonolayer depositions at 100 K the Cu grows in a dispersed mode forming 2D islands pseudomorphic to the Ru(0001) substrate upon annealing to 300 K. This behavior is seen to continue to the 1 monolayer (ML) level. Additional Cu deposition to 2 ML shows a similar 2D island growth but with an epitaxial Cu(111) structure. Subsequent annealing in both these cases to 900 K enhances the 2D character of the films but does not affect the overall structure. AES and LEED results show that a 900 K anneal of Cu films in excess of 2 ML leads to three-dimensional Cu(111) island formation exposing areas of the surface covered by the original Cu bilayer — one pseudomorphic and one epitaxial. The effects of Cu on the chemisorptive properties of Ru(0001) toward CO were also studied by TPD. It was found that Cu attenuates the CO adsorption relative to the open Ru(0001) sites on approximately a one-to-one basis. In addition, at the 1 ML level the TPD spectrum shows features which are intermediate between those for the tightly bound CO/Ru system and the weakly bound CO/Cu case. A feature in the TPD spectra of CO on submonolayer Cu deposits is identified with mixed Cu/Ru sites, i.e. at the 2D Cu island edges, and allows an estimate of the 2D Cu island sizes to be made. The results and conclusions of this study differ markedly from previous single-crystal studies but are consistent with recent observations of Cu adsorbed onto an epitaxial Ru(0001) film grown on a Mo(110) surface.

Electron paramagnetic resonance of Cu 2+ in CaWO 4

The electron paramagnetic resonance spectrum has been observed for the CU 2+ ion in a distorted tetrahedral environment in CaWO 4. The spectrum has been fitted to an axial spin Hamiltonian, leading to g-values | g ‖| = 2.072 ± 0.005 and | g ⊥| = 2.286 ± 0.005 and hyperfine splitting constants | A ‖ | = 38.5 × 10 −4 cm −1, |A ⊥ 55.6 x 10 −4 cm −1 for the 65Cu isotope and | A ‖ | = 41.1 × 10 −4 cm −17, | A ⊥ | = 59.5 × 10 −4 cm −1 for the 65 Cu isotope. The results are discussed in terms of the observations of Cu 2+ paramagnetic spectra in other tetrahedral crystal fields, and an interpretation of the present results in terms of 4 p admixture into the 3 d electronic wave function of the paramagnetic ion is suggested.