Bands Of Cu Research Articles

Controllable Preparation of a Cu NCs@Zn-MOF Hybrid with Dual Emission Induced by an Ion Exchange Strategy for the Detection of Explosives.

The precise synthesis of Cu NCs is a highly desirable and controllable route for the preparation of desired structures and properties, which facilitates the rational design of valuable probes for fluorescence sensing and the understanding of structure-property relationships. Herein, an ion-exchange strategy combined with a bottom-up synthetic approach was utilized in the synthesis process of Cu NCs for the first time, which achieved the controllable synthesis of Cu NCs and in situ anchoring of Cu NCs on the support material HPU-14. The as-prepared Cu NCs@HPU-14-4h not only had a good peroxidase-like property but also exhibited stable dual-emitting fluorescence at 470 and 620 nm. Notably, the peroxidase-like property endowed Cu NCs@HPU-14-4h with the capability of highly sensitive colorimetric detection of H2O2 in a linear concentration from 0.1 to 140 μM (detection limit of 86.7 nM), and a change in the fluorescent color from red to blue could be observed by the naked eye. Furthermore, due to the large overlap between the absorption of 2,4,6-trinitrophenol (TNP) and the excitation band of Cu NCs@HPU-14-4h, TNP could also be detected from 27 types of analogs and common ions with a limit of detection of 68 nM. Finally, a portable hydrogel probe with efficient wipe sampling was fabricated by polyvinyl alcohol (PVA) comprising Cu NCs@HPU-14-4h with the aim of on-site visualization of different explosives. Consequently, the current study not only provides a new idea for the precise synthesis of Cu NCs and their controllable anchoring on support materials but also offers an effective method for predicting H2O2 and TNP.

Local structure, spectroscopy and luminescence of the Li2B4O7:Cu,Eu glass

The Li2B4O7:Cu,Eu glass containing 1.0 mol.% CuO and Eu2O3 impurities was obtained and studied by XRD, EPR, optical absorption, and photoluminescence techniques. Parameters of local structure (interatomic distances and coordination numbers) were derived from XRD data analysis. The EPR and optical absorption, emission, photoluminescence excitation show that the Cu impurity is incorporated into the Li2B4O7 glass as Cu2+ (3d9) and Cu+ (3d10) ions. The Cu2+ ions in Li2B4O7:Cu,Eu glass show characteristic EPR and optical absorption spectra. Spin Hamiltonian parameters of the Cu2+ EPR spectrum were determined. Optical absorption spectrum of the Li2B4O7:Cu,Eu glass was analysed and interpreted. Optical band gap and Urbach energy of the Li2B4O7:Cu,Eu glass were evaluated. Photoluminescence spectra of the Li2B4O7:Cu,Eu glass reveal broad blue emission band of Cu+ (3d94s1 → 3d10 transition) and narrow emission bands of Eu3+ (4f6) ions belonging to the 5D0 → 7FJ (J = 0 – 4) transitions with characteristic decay kinetics.

Pivotal role of oxygen during the synthesis of Cu(OH)2/TiO2 and its effect on photocatalytic hydrogen production activity

Herein, we have demonstrated that the structural bonding of TiO2/Cu(OH)2 significantly changes in the presence of dissolved oxygen in water, and the photocatalytic activity directly depends on the interaction of surface species in TiO2. The Cu(OH)2/TiO2 nanostructured photocatalysts were prepared in the presence and absence of molecular oxygen. A remarkable finding of the work is that the sample prepared in the presence of oxygen produced 1169 µmol/g/h higher hydrogen than the sample prepared with nitrogen. The Cu(OH)2/TiO2 photocatalysts generated 27592 μmol/g and 22916 μmol/g of hydrogen in 4 h of reaction time under solar light irradiation for samples prepared in the presence and absence of molecular oxygen, respectively. Compared to the bare TiO2, a 60 folds enhancement in hydrogen production was observed for Cu(OH)2/TiO2, and it has been attributed to the formation of interface bonding between Cu(OH)2 and TiO2, the semi-amorphous nature of Cu(OH)2, the existence of terminal hydroxyl species on the TiO2 surface, and extended visible light absorption due to the d-d transition bands of Cu. This cost-effective and room temperature synthesis strategy provides new insight into manipulating the surface chemistry of TiO2-based photocatalysts for improved visible light absorption and charge transport dynamics.

Optical study and simulation of diffusion of copper ions in the linbo3 crystal

The article deals with research into the processes of diffusion and drift of copper ions in a lithium niobate crystal after annealing in the presence of a copper film deposited on the crystal surface. For this purpose, there are chosen temperatures T = 600, 650, 700, 750 and 800°C, with the duration of high-temperature annealing being 6 hours for each sample. The optical absorption spectra of the samples are recorded in the direction perpendicular to the direction of diffusion at different distances from the edge of the crystal. Absorption bands of Cu+ (400 nm) and Cu2+ (1000 nm) ions are observed in all the samples annealed. The intensity of the bands varies depending on the annealing temperature and the distance from the diffusion source. Concentrations of copper ions are calculated using the Smakula–Dexter formula. Depth dependences of the Cu ions concentration are approximated within the framework of the model, taking into account both diffusion and drift of Cu ions. Experimental spatial distributions of copper ion concentrations are well approximated by theoretical curves calculated within the framework of the mathematical model of diffusion. The diffusion coefficients determined from the approximations are well-agreed with the available data from the literature.

Precipitation Patterns in Reaction–Diffusion–Reaction Systems of Prussian Blue and Cu–Fe-Based Prussian Blue Analogs

In agarose gel containing [Fe(CN)6]3‒ions and sandwiched between two metal rods (Ti, Fe, or Cu) with a voltage of 1‒5 V applied for 20–100 h, reaction–diffusion–reaction (RDR) processes (that is, electrochemical reactions at metal rods to generate reactant ions, diffusion of the reactant ions influenced by the electric field in agarose gel, and reactions of the reactant ions to form/decompose precipitates) were coupled to generate diverse precipitation patterns of Prussian blues (PB) or Cu–Fe-based Prussian blue analogs (Cu–Fe PBA). These patterns strongly depended on the type of metal electrode, applied voltage, initial [Fe(CN)6]3‒concentration, and elapsed time after voltage application. Under the application of 2 V for 20/50 h, the PB/Cu–Fe PBA formed a discrete precipitation band on the anode/cathode side in an agarose gel containing 0.050 M [Fe(CN)6]3‒ions. In the Cu–Fe PBA system, a relatively long precipitation band of Cu(OH)2was also generated on the anode side by OH−ions produced on the cathode as a byproduct. Longer voltage applications promoted propagation of the Cu–Fe PBA band to the anode side and caused the discrete PB band to disappear. Higher initial [Fe(CN)6]3‒concentrations deepened the color of the generated patterns. Higher voltage applications suppressed the propagation of the Cu–Fe PBA band to the anode side and caused the PB band to disappear. Experiments using a Ti cathode suggested that the formation and subsequent decomposition of PB or Cu–Fe PBA at the cathode surface are important for forming precipitation band(s) in the gel near the cathode. The application of cyclic alternating voltages (particularly, 4 V for 1 h and 1 V for 4 h) was effective in generating Liesegang-band-like periodic bands, particularly for the Cu–Fe PBA system.

ФОРМИРОВАНИЕ ОСТРОЙ КУБИЧЕСКОЙ ТЕКСТУРЫ В ЛЕНТАХ-ПОДЛОЖКАХ ИЗ СПЛАВОВ (Cu+Ni)–Me (Me=Mo, Mn, Nb) ДЛЯ ВЫСОКОТЕМПЕРАТУРНЫХ СВЕРХПРОВОДНИКОВ ВТОРОГО ПОКОЛЕНИЯ

After cold-rolling reduction with the shrinkage of more than 97 % and recrystallization annealing, the edged cubic texture develops in some fcc lattice metals with the high and medium values of stacking fault energy such as Ni, Cu, Al, Pt, and some alloys on their base. The extended bands of metals and fcc lattice alloys can be used to apply multilayer functional compositions. The authors studied the structure and crystallographic texture in bands of three-component copper-nickel-based alloys. The study showed the crucial possibility of creating multi-component alloys based on the Cu+40% Ni binary alloy doped with such elements as Mo or Nb. The paper considers the formation of an edged cubic texture in bands of Cu–Ni–Mn, Cu–Ni–Nb, and Cu–Ni–Мо alloys produced through cold deformation with rolling and recrystallization annealing performed at different temperatures. The study identified that annealing during one hour at 1050 °С was an optimal recrystallization annealing mode when on the surface of bands made of (Cu+40 % Ni)–Me alloys (where Me=Mn, Mo, Nb) deformed at ~99 %, the most perfect cubic texture was realized. According to the data obtained, after such annealing mode, from 94% to 98% of grains with orientation {001}<100> developed in the Cu–40% Ni–1.3% Mn, Cu–40% Ni–0.8% Mo, and Cu–40% Ni–0.5% Nb alloys. It opens the prospect of using these alloys as epitaxial substrates in the technology of high-temperature second-generation superconductors. The evaluation of mechanical characteristics showed that alloying contributed to an increase in the yield strength of Cu–40% Ni–1.3% Mn, Cu–40% Ni–0.8% Mo, and Cu–40% Ni–0.5% Nb alloys by 3–4 times compared with the yield strength value of a textured copper band.

Synthesis and Structural studies of lightweight CNT/Cu composites: An overview

An overview on structural and electrical properties of carbon nanotubes (CNTs) and Copper (Cu) based composite is presented keeping in mind their applications today and in the near future. CNTs are emerging as the most promising conducting wires in interconnection technology due to their higher electrical conductivity and extraordinary current-carrying capacity. In this work, we have found that, metal sputtering technique proved useful for the deposition of Cu nanoparticles on the surface of nanotubes. The structural and morphological studies of Cu deposited nanotubes were investigated by Raman spectroscopy and scanning electron microscopy (SEM). It was found that, the presence of prominent Raman bands in Cu deposited nanotubes is clear indication of the nanocompoites formation without destruction of carbon tubular structure. CNTs/Cu composites showed high conductivity and ampacity, making it uniquely suited for applications in microscale electronics and inverters.

Structure prediction of CuBiI ternary compound and first-principles study of photoelectric properties

Ternary metal halides have attracted much attention as a new potential photoelectric material due to their ultra-high photoelectric conversion efficiencies. In this paper, USPEX, a crystal structure prediction software based on genetic algorithm, is used to investigate the potential crystal structures of ternary CuBiI compounds (CuBi<sub>2</sub>I<sub>7</sub>, Cu<sub>2</sub>BiI<sub>5</sub>, Cu<sub>2</sub>BiI<sub>7</sub>,Cu<sub>3</sub>BiI<sub>6</sub>, Cu<sub>3</sub>Bi<sub>2</sub>I<sub>9</sub>, CuBi<sub>3</sub>I<sub>10</sub>, and Cu<sub>4</sub>BiI<sub>7</sub>) at atmospheric pressure and absolute zero temperature. Based on the density functional theory, the formation energies, elastic coefficients, and phonon dispersion curves of the predicted structures are calculated. The twelve stable CuBiI compounds with good thermodynamic, dynamical and mechanical stabilities are identified. The twelve crystal structures of CuBiI compound feature mainly the co-existence of Cu—I and Bi—I bonds and coordination polyhedrons of I atoms. The band gaps of twelve structures, calculated by HSE06 method, are 1.13–3.09 eV, indicating that the stoichiometric ratio affects the band gap obviously. Among them, the band gaps of Cu<sub>2</sub>BiI<sub>5</sub>-<i>P</i>1, Cu<sub>2</sub>BiI<sub>7</sub>-<i>P</i>1 and Cu<sub>2</sub>BiI<sub>7</sub>-<i>P</i>1-II are relatively small, close to the optimal band gap value for light absorption (1.40 eV), demonstrating that these compounds are suitable for serving as light absorbing materials in solar cells. The distribution of density of state (DOS) indicates that the top of the valence band of CuBiI compound is attributed to the hybridized Cu-3d and I-5p orbitals; the bottom of the conduction band of Cu<sub>3</sub>BiI<sub>6</sub>-<i>R</i>3 comes mainly from the Bi-6p and I-5p orbitals, and Cu-3d contributes little; the conduction band bottom of Cu<sub>2</sub>BiI<sub>7</sub> is mainly from the I-5p orbital, and the Cu-3d has little contribution. The bottoms of the conduction band of other structures originate mainly from the hybridized Bi-6p and I-5p orbitals. Electronic localization function and Bader charge analysis show that the Cu—I and Bi—I bonds have more ionic features and less covalent natures. The DOS distribution also confirms the covalent interaction of Cu/Bi-I. In addition, the CuBiI ternary compounds have extremely strong light absorption capacities (light absorption coefficient higher than 4 × 10<sup>5</sup> cm<sup>–1</sup>) in the high-energy region of visible light and high power conversion efficiency (31.63%), indicating that the CuBiI ternary compounds have the potential to be an excellent photoelectric absorption material. Our investigation suggests the further study and potential applications of CuBiI ternary compound as absorber materials in solar cell.

Isomerism, conformation, and structure of Bis(4,4-dimethyl-1-phenylpentane-1,3-dionato)copper(II); A theoretical and spectroscopy approach

Cis and trans isomerism, conformers, molecular structure, relative energies, spectroscopic analysis, metal-ligand strength, and complete vibrational assignment of bis(4,4-dimethyl-1-phenylpentane-1,3-dionato) copper (II), Cu(dmpd)2, were investigated by applying calculated parameters such as density functional theory (DFT), Atoms in Molecules (AIM) study at the B3LYP/6-311G(d) level of theory and experimental techniques contains of vibrational spectra and UV spectroscopy. A comprehensive assignment of the experimental bands of Cu(dmpd)2 has been done. The DFT and spectroscopy techniques applied to consider the assessment of methyl and phenyl and t-But substituents in the β-position on the geometrical and vibrational analysis of complexes. So, the structure, Cu-O strength of the complex, UV spectrum, and vibrational bands of Cu(dmpd)2 compared to bis(benzoylacetonato) copper (II), Cu(bzac)2 and bis(2,2,6,6-tetramethylheptane-3,5-dionato)copper(II), Cu(tmhd)2, by the mentioned theoretical and experimental techniques. All of the simulated and spectroscopic methods supported that the Cu-O bond strength of Cu(dmpd)2is closeto Cu(bzac)2 and more than that Cu(tmhd)2 complex. Comparing the experimental and theoretical vibrational wavenumbers indicates that the transform is the major configuration in the specimen, which agrees with reported the single crystallography results.

Luminescent properties of Cu+ doped aluminosilicate glasses: Effect of optical basicity and doping content

Various Cu+ doped transparent aluminosilicate glasses were elaborated by melt quenching method. X-ray diffraction (XRD), transmission spectra, luminescent spectra and fluorescence decay curves were used to study their structural and luminescent properties systematically. By increasing optical basicity of glasses, excitation and emission peaks of Cu+ shift from 300 to 321 nm and from 445 to 536 nm, respectively. Furthermore, longer excitation (330 nm) and emission wavelengths (545 nm) are realized via growing Cu+ concentration. It suggests that the absorption and emission band of Cu+ in aluminosilicate glasses can be modified by altering the optical basicity of glass composition and Cu+ content. More importantly, the as-prepared Cu+ doped glasses show highly external quantum yields (35.8–57.4%) and excellently thermal stability. At 428 K, Cu+ doped glass excited by 330 nm can keep 75% emission intensity of that at 308 K. And chromaticity shows only a tiny shift with increasing temperature. Our research may provide a strategy for extending the practical application of Cu+ doped transparent luminescence glasses.

Effect of substitutional Cu atoms on the electronic and optical properties of KCl: A DFT approach

The electronic and optical properties of KCl and Cu doped KCl (KCl:Cu) were calculated within full potential augmented plane wave method based on Density Functional Theory (DFT), as implemented in WIEN2k software. Calculations were carried out using two energy functional approximations, the exchange-correlation functional of Perdew, Burke and Ernzerhof (PBE96) to optimize the KCl lattice parameter, and the modified Becke-Johnson (mBJ) exchange potential in combination with the local density approximation (LDA) for correlation, to obtain the band structure. The energy bands reveal the insulating properties of KCl with a direct band gap of 8.6 eV, and the semiconductor nature of KCl:Cu with a direct band gap of 3.4 eV. From the analysis of the total and partial density of states, it is apparent that the KCl and KCl:Cu states at the Fermi level arise from Cl p states and Cu d states, respectively. Also, the optical properties reported here (dielectric function and absorption spectra) show that Cu atoms are responsible of electronic excitations occurring from Cu d valence bands to conduction bands of Cu, Cl and K with p character.

Spatiotemporal analysis of a final-state shape resonance in interferometric photoemission from Cu(111) surfaces

Photoemission from solid targets includes the excitation and motion of electrons inside the substrate, followed by their propagation in vacuum and detection. It thus depends on the electronic band structure of the solid in the two distinct spectral domains of bound initial and continuum final states. While the imprint of the static (initial-state) valence electronic structure of solids on photoemission spectra is routinely examined in standard photoemission spectroscopy in the energy domain, state-of-the-art time-resolved photoelectron spectroscopy allows, in addition, the scrutiny of photoelectron propagation in the electronic continuum. Within a quantum-mechanical model for attosecond time-resolved interferometric photoelectron emission from solids, we calculated photoemission spectra as a function of the delay between the exciting primary attosecond pulse train and assisting infrared (IR) laser pulse. Accounting for final-state interactions of the photoelectron with the IR laser electric field and the periodic substrate, our numerical results for interferometric photoemission from the $3d$-valence band of Cu(111) surfaces show a striking resonantly enhanced sideband yield at photoelectron kinetic energies near $24\phantom{\rule{4pt}{0ex}}\mathrm{eV}$, in conjunction with a pronounced increase of the photoelectron wave-function amplitude inside the solid on a length scale of a few nanometers. This resonant shift of final-state photoelectron-probability density towards the bulk can be interpreted as an increase in the photoelectron propagation time in the solid and is commensurate with the resonantly enhanced spectral sideband-phase shifts observed in recent two-pathway two-photon interference spectra by Kasmi et al. [Optica 4, 1492 (2017)].

Influence of Optical Basicity on Cu+ Luminescence in Aluminosilicate Oxyfluoride Glasses

Cu+-activated aluminosilicate oxyfluride glasses were successfully synthesized by melt quenching method in air with adding Al powder as reducing agent. Their luminescent properties were studied systematically via optical absorption, excitation and emission spectra. Upon UV irradiation, a blue-emitting band of Cu+ with relatively low optical basicity is observed. By increasing optical basicity of glass, obviously red shifts of excitation (290→313 nm) and emission (435→470 nm) peaks can be obtained. Through enhancing Cu+ content, excitation and emission bands present further redshifts, which shift from 313 to 338 nm and from 470 to 560 nm, respectively. It is proposed that the absorption band and emitting color of Cu+-doped glass could be tuned by changing the optical basicity of glass and Cu+ concentration. The highest quantum yield can reach 62.5%. More importantly, investigation of the thermal stability displays that over 91% of the room temperature luminescent intensity still preserves at 200 °C. These results infer that Cu+-activated aluminosilicate oxyfluride glasses may be utilized for UV converted W-LEDs.

Quantum confinement in free Cu(111), Ag(111), and Au(111) layers and apparent splitting of surface bands

The apparent splitting of surface bands of Cu(111), Ag(111), and Au(111) films, obtained in calculations without account for spin-orbit coupling, is usually explained as a result of interaction of surface states located at opposite surfaces of the slabs. However, such twinning of the surface states is absent for other surfaces of noble metals despite the anticipated similar interaction. Here we suggest an alternative explanation and attribute the twinning of the bands to the quantum confinement effect.

Potential role of serotonin as a biological reductant associated with copper transportation

Serotonin (5-HT) is a neurotransmitter that is derived from tryptophan. Owing to a hydroxyl group attached to the indole nucleus, 5-HT exhibits a considerably higher redox activity than tryptophan. To gain insight into the biological relevance of the redox activity of 5-HT, the effect of Cu(I)-binding ligands on the 5-HT-mediated copper reduction was investigated. The d-d transition band of Cu(II) complexed with glycine [Cu(II)-Gly2] was not affected by addition of 5-HT alone but was diminished when a thioether-containing compound coexists with 5-HT. Concomitant with disappearance of the d-d transition band of Cu(II)-Gly2, the π-π* transition band of 5-hydroxyindole of 5-HT exhibits a red-shift which is consistently explained by oxidation of 5-HT and subsequent formation of a dimeric species. The redox reactions between 5-HT and copper are also accelerated by a peptide composed of a methionine (Met)-rich region in the extracellular domain of an integral membrane protein, copper transporter 1 (Ctr1). Since Ctr1 transports copper across the plasma membrane with specificity for Cu(I), reduction of extracellular Cu(II) to Cu(I) is required for copper uptake by Ctr1. Metalloreductases that can donate Cu(I) for Ctr1 have been identified in yeast but not yet been found in mammals. The results of this study indicate that the Met-rich region in the N-terminal extracellular domain of Ctr1 promotes the 5-HT-mediated Cu(II) reduction in order to acquire Cu(I) via a non-enzymatic process.

Effect of solvent on the electronic absorption spectral properties of Ni(II) and Cu(II)-complexes of some mixed β-octasubstituted-meso-tetraphenylporphyrins

A series of mixed β-substituted porphyrins, 2,3,12,13-tetrakis(bromo/cyano/methyl)-5,7,8,10,15,17,18,20-octaphenylporphinatonickel(II)/copper(II), MOPPX4s (X = Br, CN and CH3; M = Ni(II) and Cu(II)) were examined in 24 different solvents with varying polarity. Among the porphyrins, MOPP(CN)4 show enhanced solvent dependent optical absorption spectral features relative to other porphyrins, MOPPX4 (X = Br and CH3) and MTPPs. Although, MOPP(CN)4 (M = Ni(II) and Cu(II)) have higher electron deficiency due to electron withdrawing β-cyano groups, comparable solvent dependent absorption spectral features and opposite trend in their shift of bands relative to the corresponding MTPPBr8 were observed. The large red-shift of the absorption bands of Cu(II) and Ni(II)-mixed substituted porphyrins in polar solvents or nitrogenous bases has been suggested to the destabilization of the HOMO (b2) relative to b1 (HOMO) level due to axial ligation of the polar solvents or nitrogenous bases with the core metal ions. The greater affinity of the core metal ions towards coordinating solvents or nitrogenous bases has been attributed to the electron deficient nature of the porphyrin π-system and follow the order: MOPP(CN)4 > MOPPBr4 > MOPP(CH3)4 due to inductive/resonance effect of β-substituents rather than the nonplanarity of the porphyrin ring.

Critical operating stress of persistent slip bands in Cu

This work elucidates the dependence of operating stress of persistent slip bands (PSB) on the channel width and wall dislocation density. Using Cu as a model system and molecular dynamics as the main investigative tool, a new length scale effect, namely the wall dislocation spacing, is provided to enhance theoretical understanding of PSBs. It is discovered that the operation of PSB is a thermally activated event in which operating stress is inversely related to the wall dislocation spacing, strain rate and temperature. Leveraging the existing framework of confined layer slip in nanoscale metallic multilayers and classical nucleation theory, a mathematical model describing the rate- and temperature- dependent PSB operating stress is proposed.

CuO and Au-CuO nanoparticles mediated by Stigmaphyllon ovatum leaf extract and their anticancer potential

The synthesis of nanoparticles by green methods, utilizing the extracts from plants has become viable alternative routes for nanomaterial synthesis. The method avoids the expensive and toxic materials used during chemical syntheses. The incorporation of plant extracts with favourable biological properties into nanoparticles has beneficial relevance in the biomedical field. In this study, CuO and Au-CuO nanoparticles were synthesized using the aqueous extract of the Stigmaphyllon ovatum plant and characterised. Optical studies produced peaks around 290 and 670 nm in both nanomaterials, and can be attributed to electron transition and the surface plasmon bands of Cu. The spectra of the Au-CuO nanohybrid showed a broad band around 564 nm due to Au doping. Band gap energies of 3.25 and 3.17 eV were obtained for the CuO and Au-CuO nanohybrids, respectively. The photoluminescence spectra at an excitation wavelength of 200 nm gave different peaks with the near band edge at 300 nm. The synthesized nanoparticles were further evaluated as potential anticancer agents in HeLa cells, and exhibited good anticancer potency with Au-CuO having the greatest activity. The IC50 values for CuO, Au-CuO nanomaterials and the control drug (5-fluorouracil) were 12.3, 112 and 40 μM respectively.

Electron Transport in Graphene-Versus Al/Pd-Coated Thin Cu Films With Low-Surface Roughness: A First Principles Study

Surface scattering is a major issue in thin Cu films at reduced scales. The rise in the diffusive scattering due to the surface roughness causes the electrical resistance to increase remarkably. In this paper, graphene, as opposed to Al and Pd, is considered as a liner layer for thin Cu film with low-surface roughness using first principles calculation. The surface roughness is simulated using the nonequilibrium coherent potential approximation combined with the linear muffin-tin orbital formulation. The coherent potential approximation band structure shows that the graphene $\pi $ -bands is not significantly affected by the surface disorder at the Cu surface and that graphene acts as a parallel path to the electrons. On the other hand, the bands of Cu–Al/Pd around the Fermi level are substantially broadened due to the surface disorder. Moreover, the graphene-coated Cu shows less electrical resistance than Al/Pd-coated Cu for surface disorder $x\lessapprox 5$ % for thin films with 0.245 nm in width, and 1.23 nm in thickness. The enhancement in the transport properties in Cu–Gr is attributed to the weak electronic interaction at the interface. The obtained results suggest that graphene is better than Al and Pd as a liner material for thin Cu films.

Splitting of Shockley surface states in thin films of noble metals

The splitting of the surface bands of Cu(1 1 1), Ag(1 1 1), and Au(1 1 1) films is studied by means of relativistic density-functional theory (DFT) calculations. It is found that the splitting of the bands of clean films obtained in semirelativistic approximation, in agreement with previous studies, stems from the interaction between the surfaces and hence depends on the thickness of the slabs. Since the Kramers’ degeneracy is not broken by the presence of the surface, the spin-orbit coupling does not lead to the spin-splitting of the bands. An H monolayer, deposited on one face of the film, breaks the inversion symmetry and results in the appearance of the Rashba-type splitting of the bands.