Compositional modulation of CuZn,CuAl and CuNi alloys

A differential reflectometer that is capable of measuring small differences in optical reflectivity or transmissivity of two specimens and therefore enhances the structure in the spectral reflectivity of materials was used to study various α-Cu-Zn, α-Cu-Al, and Cu-Ni alloys with the aim of investigating the changes in band structure as a function of composition. In Cu-Zn and Cu-Al alloys three main absorption peaks were identified that were associated with the Δ₅ → Δ₁, X₅ → X_4' and L_2' → L₁sitions. It was found that the Δ₅→ Δ₁transition increases slightly in energy with increasing Zn or Al concentration. These transitional energies are identical for both alloys in the entire α-phase region. The X₅ → X_4' and L_2' → L₁ transitions decrease in energy with increasing solute concentration. The shift in energy is significantly larger for the Cu-Al system. In Cu-Ni alloys no shift of the absorption edge around 2.2 eV was found, which is consistent with the predictions of the virtual-bound-state model.     

Meissner effect in Cu of thick Cu clad Nb

The Meissner region induced by the proximity effect in the thick Cu clad wire is measured down to 21 mK. It is found that the thickness ? of the Meissner region in Cu becomes very large and still increases even at the lowest temperature in proportion to $\text{T}{}^{\mathrm{<mtext>-</mtext><mtext>1</mtext><mtext>2</mtext>}}$. At low temperatures, ? becomes very sensitive to the magnetic field. Especially below about 40 40 mK, an abrupt decrease of ? is observed below about 200 mOe in increasing magnetic field.     

金刚石薄膜在多晶铜和磷脱氧铜基片上的生长

分别采用99.99%的多晶铜片和99.95%的磷脱氧铜片作为沉积金刚石薄膜的基片，通过热丝化学汽相沉积法在两种基片上都获得了大面积、自支撑的多晶金刚石膜.使用高分辨率光学显微镜、扫描电子显微镜、Raman光谱和X射线衍射比较分析了两种铜基片上的金刚石膜.脱氧铜上的金刚石膜质量并不亚于多晶铜上的金刚石膜，而且它的成核密度、生长速率以及应力都高于多晶铜上金刚石膜的同类参数.特别采用了退火工艺和优化的生长条件来获得大面积的连续金刚石膜. 关键词：     

Neutron channeling in layered Cu/Ti/Cu structures

The phenomenon of neutron channeling in layered structures is considered. Experimental data for the neutron channeling length in layered Cu/Ti/Cu structures obtained in Dubna (Russia) and Grenoble (France) in 2000–2002 are presented. A conclusion about the necessity of further studies of neutron channeling in multilayer structures is drawn.     

Cu nuclear spin-spin relaxation in YBa2Cu3O6.98 and YBa2Cu4O8

We have measured the temperature (T) dependence of the transverse relaxation rate (T _G ^–1 ) of the Cu(1) nuclear spin in YBa₂Cu₃O_6.98 (T _c=92 K) and YBa₂Cu₄O₈ (T _c=82 K). From the scaling ratio ofT _G ^–2 (Cu1) toT _G ^–2 (Cu2), we have estimated the strength of a covalent bonding between the CuO₂ plane and the CuO chain to be B0.38×A _zz. The experimentalT _G ^–1 (Cu1) in YBa₂Cu₄O₈ was of the same order of magnitude as the estimated one fromT _G ^–1 (Cu2). These results appear to indicate that the electrons in the CuO₂ plane fairly spread out of the plane in both compounds.     

On the Auger-photoelectron coincidence spectroscopy spectra of Cu(100), Cu metal and CuOx/Cu surface

The M₃–VV Auger-photoelectron coincidence spectroscopy (APECS) spectrum of Cu(100) and the L₃–VV APECS spectra of Cu metal and CuOx/Cu surface are analyzed in detail. The narrowing and energy shift of the photoelectron line in the M₃–VV APECS spectrum is well predicted by the present theory. The spectrum shows the presence of the M₂–M₃(V)–VV(V) decay in which a hole in the 4s band hops away prior to the decay of M₃ hole. The analysis of the L₃ photoelectron spectra of Cu metal measured in coincidence with the ³F or ¹G Auger line raises a question concerning the presence of two different core–hole states upon the L₃ level ionization recently proposed by Thurgate and Jiang [Surf. Sci. 466 (2000) L807]. The analysis of the L₃–VV APECS spectrum of CuOx/Cu shows that the final-state charge–transfer interaction plays an important role in CuO.     

Quantum confinement in monatomic Cu chains on Cu(111)

The existence of one-dimensional (1D) electronic states in Cu/Cu(111) chains assembled by atomic manipulation is revealed by low-temperature scanning tunneling spectroscopy and density functional theory (DFT) calculations. Our experimental analysis of the chain-localized electron dynamics shows that the dispersion is fully described within a 1D tight-binding approach. DFT calculations confirm the confinement of unoccupied states to the chain in the relevant energy range, along with a significant extension of these states into the vacuum region.     

63Cu and65Cu Fourier transform nuclear magnetic resonance studies

⁶³Cu and⁶⁵Cu NMR studies are reported in liquid and solid copper (I) compounds. Ratios ofg _I-factors, nuclear magnetic moments and nuclear magnetic shielding constants in the atomic reference scale are given for⁶³Cu and⁶⁵Cu in a solution of Cu(I)(CH₃CN)₄BF₄ in CH₃CN, which is a reasonable reference sample due to the relatively narrow NMR line.     

Localization of the Cu111 surface state by single Cu adatoms

The Cu adatom-induced localization of the two-dimensional Shockley surface state at the Cu(111) surface was identified from experimental and simulated scanning tunneling microscopy spectra. The localization gives rise to a resonance located just below the surface state band edge. The adatom-induced surface state localization is discussed in terms of the existence theorem for bound states in any attractive two-dimensional potential. We also identify adatom-induced resonance states deriving from atomic orbitals in both experimental and simulated spectra.     

Synthesis and thermoelectric properties of Cu excess Cu2ZnSnSe4

Quaternary stannites with an excess of copper were successfully synthesized by reacting the constituent elements and subsequent solid state annealing, followed by densification by hot‐pressing. The composition for each specimen was confirmed with a combination of Rietveld refinement and elemental analysis. Their high temperature thermoelectric properties were measured from 300 K to 800 K and compared with that of Cu₂ZnSnSe₄. The thermal conductivity decreases significantly with increasing Cu content at elevated temperatures due to the crystal structure of this material system. A maximum ZT value of 0.86 was obtained at 800 K for the specimen with the highest Cu content, Cu_2.2Zn_0.8SnSe₄. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Diffusion mechanism of Cu adatoms on a Cu(001) surface

Ab initio calculations on surface diffusion of Cu adatoms on Cu(001) are presented. The hopping mechanism with a calculated energy barrier of 0.69 eV is found to be favorable over the exchange mechanism with 0.97 eV. We find from the geometry relaxations that adatoms are significantly attracted to the surface and push away nearest-neighbor atoms in the surface. Lateral relaxations of atoms in the surface are larger than vertical ones.     

Formation and diffusion of S-decorated Cu clusters on Cu(111)

S-decorated Cu trimers are a likely agent of S-enhanced Cu transport between islands on Cu(111). According to ab initio calculations, excellent S bonding to trimer-Cu dangling valence results in an ad- Cu(3)S(3) formation energy of only approximately 0.28 eV, compared to 0.79 eV for a self-adsorbed Cu atom, and a diffusion barrier < or =0. 35 eV.     

Investigation of agglomerated Cu seed on Cu oxidation after chemical mechanical planarization

After chemical mechanical planarization (CMP), the reason which caused the formation of Cu-oxide defects at the interface between Cu deposit and TaN barrier layer has been studied. The experimental results of atomic force microscopy, secondary ion mass spectroscopy, X-ray diffraction demonstrated that the agglomeration phenomenon was found on Cu seed in the thickness of only 10 nm, thus resulting in the electrodeposited Cu film with more abundant C impurities at Cu/TaN interface and lower (1 1 1)/(2 0 0) ratio compared to the thick one (30 nm). Therefore it caused the Cu deposit with poor corrosion resistance and then the Cu-oxide defects were easily formed after CMP. As a result, the correlation between Cu-oxide defects at the Cu/TaN interface and the agglomeration on Cu seed layer was proposed herein.     

Scattering by Cu adatoms between image-potential bands on Cu(001)

With the increasing resolution and sensitivity of photoelectron spectroscopy, the influence of defects is becoming more and more obvious. Scattering processes induced by adsorbate atoms can be studied by time- and angle-resolved two-photon photoemission. We have examined the dynamics of electrons in image-potential states on the Cu(001) surface for statistically distributed Cu adatoms and have identified different scattering mechanisms. Scattering of electrons from the second (n=2) to the bottom of the first (n=1) image-potential band is observed, which we attribute to inelastic interband scattering with electrons in the bulk. At energies above the bottom of the n=2 band, resonant interband scattering from the n=2 to the n=1 image-potential band is found. The rate for these processes can be determined by modeling the time-resolved measurements via optical Bloch equations of a four-level system. Comparison of the transition and decay rates reveals that the decay rate of the n=2 electrons is almost exclusively changed by additional resonant interband-scattering processes upon adsorption. PACS 73.20.At; 79.60.Ht; 68.49.Jk     

Anomalous mechanical characteristics of Au/Cu nanocomposite processed by Cu electroplating

An Au/Cu nanocomposite is produced by electroplating Cu on a nanoporous Au, and its mechanical characteristics are investigated by hardness tests. The Au/Cu nanocomposite showed a lower hardness and a lower elastic modulus than the nanoporous Au. Furthermore, annealing caused the nanocomposite to harden twice. Large lattice strains in the Au lattice for the nanocomposite were observed by high-resolution transmission electron microscopy. Also, first-principle calculations showed that lattice strains induce the decreased elastic modulus. Therefore, both the inverse mixing behaviour and the hardening via annealing are suggested to be related to the large lattice strains.