Copper Single Crystal Surfaces Research Articles

Carbon-halogen bond dissociation on copper surfaces: effect of alkyl chain length

Carbon-halogen bond dissociation in a series of straight-chain alkyl halides adsorbed on single crystal copper surfaces has been studied by high-resolution electron energy loss spectroscopy, temperature-programmed desorption, and work-function measurements. For two or more carbons in the alkyl chain, the rate of carbon-halogen (C-X) bond dissociation is indepcndent of chain length, despite the fact that the heat of molecular adsorption (assuming a first-order preexponential factor of 10 13 , s -1 for desorption) increases at the rate of 1.3±0.2 (kcal/mol)/CH 2 group

Nucleation and growth of diamond on carbon-implanted single crystal copper surfaces

The nucleation and growth of diamond crystals on single crystal copper surfaces has been studied. Microwave plasma enhanced chemical vapor deposition (MPECVD) was used for diamond nucleation and growth. Prior to diamond nucleation, the single crystal copper surface is modified by carbon ion implantation at an elevated temperature (∊820 °C). This procedure leads to the formation of a graphite film on the copper surface, resulting in an enhancement of diamond crystallite nucleation. A simple lattice model has been constructed to describe the mechanism of diamond nucleation on graphite as 〈111〉diamond parallel to 〈0001〉graphite and 〈110〉diamond parallel to 〈11$\overline 1$0〉graphite. This leads to a good understanding of diamond growth on carbon-implanted copper surfaces.

Determination of the orientation of methoxy on Cu(111) using X-ray photoelectron diffraction

The orientation of methoxy (CH 3O−) on copper single-crystal surfaces, has been the subject of some controversy. Here we show, using the particularly direct technique of X-ray photoelectron diffraction, that on Cu(111) methoxy is clearly adsorbed with its OC molecular axis perpendicular to the surface. This agrees with the results of vibrational and electronic spectroscopies, and of scanned energy mode photoelectron diffraction.

Mechanism for diamond nucleation and growth on single crystal copper surfaces implanted with carbon

The nucleation and growth of diamond crystals on single-crystal copper surfaces implanted with carbon ions has been studied. Microwave plasma-enhanced chemical vapor deposition was used for diamond growth. The single-crystal copper substrates were implanted either at room temperature or at elevated temperature (∼820 °C) with carbon ions prior to diamond nucleation. This procedure leads to the formation of a graphite film on the copper surface which greatly enhances diamond crystallite nucleation. From our study we construct a simple lattice model for diamond growth on graphite as 〈111〉diamond parallel to 〈0001〉graphite and 〈110〉diamond parallel to 〈112̄0〉graphite.

Creation of Dislocations in a Shall Copper Single Crystal

AbstractEdge dislocations were created on a surface of a small copper single crystal. Very sharp yield stress was observed when a partial dislocation was created. Edge dislocations in copper were split into Heidenreich–Shockley partial dislocations connected with the stacking fault.

High Resolution Leed Study of The Fe Growth Mode on Cu(100), Cu(110) and Cu (111) Surfaces

ABSTRACTWe have investigated the growth mode of iron on clean Cu(100), Cu (110) and Cu(111) surfaces using high resolution LEED. We studied the effect of substrate temperature on the growth of epitaxial fee iron. Iron metal was evaporated from an electron beam source under UHV conditions and deposited on the copper single crystal surfaces at three different temperatures (173 K, 300 K and 473 K). A high resolution LEED system was used to measure the diffraction spot profiles. The samples were studied as a function of temperature after deposition on the copper substrates. The clean Cu surfaces were also measured and used as references for the Fe:Cu system. The diffraction spot profiles show Gaussian line shape before and after the Fe deposition. The effect of iron grown on the Cu surface is to reduce the coherent length. This effect is observed for all the copper surfaces. The intensity of the diffraction spots exhibit a sudden increase above 470 K, simultaneously a larger coherent length is observed. This effect occurs for all copper surfaces. The epitaxial growth of Fe is better on Cu (100) than on the other surfaces. The best epitaxial growth is obtained for the highest substrate temperature. A careful Auger study reveals that the anomalous increase observed on the intensity of the diffraction spots is related to the evaporation of iron from the copper surface. The spot profiles at low temperature are very broad and are suggestive of very poor epitaxy, random islands growth with a high probability of bec iron inclusions.

Co adsorbed on Cu(100): RAIRS at ultrahigh vacuum and higher pressures

The potential of RAIRS for in-situ studies of surface species on metal single crystals under catalytic conditions is complicated by the sensitivity of such surfaces to low levels of contaminants. Using a new cell for combined UHV and higher pressure adsorption on Cu(100), the cause of previous anomalous IR spectra of CO on copper single-crystal surfaces at room temperature has been shown to be iron carbonyl. Auger spectra suggest that iron is incorporated into the copper. With purified CO the band observed at 2086 cm–1 under UHV conditions at 120 K shows a small but significant shift to 2076 cm–1 at 2.7 kPa and 300 K, falling to 2071 cm–1 at 44 Pa. Under these conditions preadsorbed oxygen is reduced and produces no shift. Residues from iron carbonyl cause shifts to lower wavenumber. Preadsorbed potassium led to the appearance of bands at 2069 and 1950 cm–1, corresponding to CO species reversibly and irreversibly adsorbed at 300 K and 1.2 kPa.

Dynamics of CuF desorption in the etching reaction of fluorine with single-crystal copper surfaces

Dynamics of CuF desorption in the etching reaction of fluorine with single-crystal copper surfaces

Young液によるCu単結晶(111)面の溶解速度の温度依存性

The effect of etching temperature on the dissolution rates at edge dislocation sites and dislocation-free sites of the (111) surface of copper single crystals was studied. The etching was carried out at temperatures 270 to 285 K for 5 to 25 s with Young’s etchant containing (NH4)2S2O8 1 kmol·m−3, NH4OH 6 kmol·m−3 and NH4Br 0.3 kmol·m−3. From the measured data on the width and depth of dislocation etch pits and the dissolved thickness of the (111) matrix surface as a function of etching time, the linear dissolution rates parallel and normal to the surface at dislocation sites, vh and vd, and the dissolution rate normal to the surface at dislocation-free sites, vs, were calculated. As a result, it was found that the dissolution rates were in the order of vh>vd>vs at any temperature and that they increased as the etching temperature increased. These results were qualitatively discussed by the kinetic theory of two-dimensional nucleation and step motion for crystal dissolution and some kinetic quantities relating to the formation of two-dimensional nucleus and the step motion were evaluated.

Impedance Studies of Copper in Alkaline Solutions, Especially During Electroless Plating

AbstractAn impedance study of the electrochemical double layer of copper in an electroless copper plating bath was performed. Of the bath components (formaldehyde, ethylenediamine‐tetraacetic acid (EDTA), CuEDTA2−, NaOH, Na2SO4, and NaHCOO) only the influence of hydroxide on the double layer is visible from capacitance data. The estimated surface coverage of hydroxide at the mixed potential of the electroless plating process is about 10%. On copper single crystal surfaces the OH−‐adsorption shows specific characteristics. Due to a surface reconstruction these characteristics, however, disappear with time after the immersion of the electrode. During the deposition process high electrode capacitances are measured (200–500 μF/cm2). They are mainly caused by a surface roughness on the microscopic scale. When the deposition process is terminated, the surface relaxes within about 10 minutes. The addition of cyanide or Gafac (a mixture of organic esters of phosphoric acid) to the electroless plating bath markedly influences the capacitance data. However, always a correlation between the deposition rate and the electrode capacitance is observed. If, on the other hand, at potentiostatic cupric ion reduction formaldehyde in the plating bath is substituted by ethylenediamine, which also catalyzes the CuEDTA2−‐reduction, the capacitance values decrease with increasing deposition current. Presumably, in the first case the nucleation rate dominates the deposit growth, while in the second case the opposite is true.

A FT-IRAS study of the vibrational properties of CO adsorbed on Cu/Ru(001). II. The dispersion of copper

The dispersion of copper adsorbed on a Ru(001) substrate has been investigated by using Fourier transform-infrared reflection absorption spectroscopy (FT-IRAS) and carbon monoxide as a molecular probe. Copper films evaporated at 85 K show a drastically different CO adsorption behavior compared to annealed films and exhibit a variety of adsorption sites. Characteristic C–O stretching frequencies allow us to identify small copper clusters of 1–4 atoms (2138–2123 cm−1), two-dimensional (2120–2110 cm−1) and three-dimensional (2098 cm−1) copper aggregates. After annealing to 250 K copper films at sub- and monolayer coverages form well-ordered small two- and three-dimensional copper aggregates. Formation of the epitaxial monolayer or islands of copper (2082 cm−1) requires a surprizingly mild annealing temperature of 350 K. Further annealing to 540 K results in increasing domain size of the copper islands or annealing of defect sites of the epitaxial monolayer. Multilayer coverages of copper evaporated at 85 K exhibit C–O stretching frequencies found for high-index copper single crystal surfaces, e.g., (211) and (755). This indicates a large number of surface steps and protruding copper atoms associated with rough films. Annealing to 540 K results in a smooth copper layer with preferential (111) orientation (2075 cm−1). The vibrational data presented here for Cu–Ru(001) agree well with previous reports of CO adsorption on copper single crystals, supported or evaporated films, and matrix-isolated clusters. They further allow us to determine the dispersion of supported Cu–Pt and Cu–Ni catalysts from data in the literature.

Transmission electron microscopy of carbon-implanted {111} copper surfaces

Carbon ions with an energy of 150 keV were implanted in {111} surfaces of copper single crystals at doses of 1016 C+ cm−2 and 1017 C+ cm−2. The radiation damage below the implanted surfaces was examined by transmission electron microscopy of cross sections of the surface regions. The effects of annealing for 30 min at 600 and 750 °C were also studied. Damage consisted of a band of small defect clusters, dislocation loops, and dislocations in the band and extending from it. The depth of this band is approximately 40% deeper than that predicted from ion range theory, and the reason for this is not clear. The range increases with larger dose. The dislocation structures are consistent with the strains due to swelling being accommodated by dislocations.

Structural specificity in CO and H 2 oxidation over single crystal copper surfaces

Structural specificity in CO and H 2 oxidation over single crystal copper surfaces

Structural specificity in CO and H 2 oxidation over single crystal copper surfaces

The reaction rates of CO and H 2 with preadsorbed oxygen on copper surfaces in the 〈110〉 zone presented by a cylindrical single crystal are found to display strong structural sensitivity. In both cases the highest reaction rates are observed for surface structures involving both steps and low index face terraces, and in particular surfaces vicinal to {311} and between either {111} or {100} are found to exhibit the highest rates of reaction. Possible mechanisms for the reaction are discussed, and the data are extrapolated to investigate the steady state oxidation of CO in a CO/O 2 gas mixture over copper surfaces in the 〈110〉 zone. The semi-empirical model describing the steady state oxidation reaction predicts that this reaction also exhibits marked crystallographic anisotropy at CO/O 2 partial pressures chosen to maximise the reaction rate.

Infrared laser stimulated desorption of adsorbates on metal surfaces

An adsorbate is irradiated by a pulsed infrared laser beam tuned in resonance with an internal vibrational mode of the adsorbed molecules. The adsorbate vibrational energy damps into the metal by electron-hole pair creation. This energy transfer from the infrared laser beam to the substrate competes with the direct optical absorption by the metal. Both mechanisms lead to a transient increase of the substrate surface temperature and to a partial desorption of the adsorbate. The resonant infrared laser stimulated desorption of NH 3 from a copper single crystal surface is analyzed quantitatively within the framework of this model. The adsorption energy of the photodesorbed molecules and the infrared absorbance of the adsorbate can be determined from the experimental data.

Surface topography and crack initiation in emerging persistent slip bands in copper single crystals

The surfaces of copper single crystals oriented for single slip and fatigued at room temperature at a constant plastic strain amplitude were observed by scanning electron microscopy. Both well-developed and embryonic stages of persistent slip band formation were found. The surface relief at the emerging persistent slip band is characterized by tongue-and ribbon-like intrusions and extrusions. The correlation of the surface relief with the dislocation arrangement in the persistent slip band was determined. The mechanism of fatigue crack initiation by interconnecting tongue-like intrusions is discussed.

Two-dimensional electron-positron momentum measurement at a copper single-crystal surface.

We report the first two-dimensional momentum measurements of annihilating positron-electron pairs at a solid surface. Positrons of 18 keV or 740 eV impinged on a clean Cu(121) surface. The 740-eV spectrum was resolved into two components, one associated with energetic positronium emission displaced from zero momentum and a second centered on zero momentum with distinct asymmetry for the directions parallel and perpendicular to the surface. The 18-keV spectrum was dominated by positron Bloch-state annihilation.

The stability of CuO and Cu 2O surfaces during argon sputtering studied by XPS and AES

CuO and Cu 2O layers were prepared on a copper single crystal surface by gas phase oxidation. The copper oxides were investigated by means of XPS and AES before and after sputtering with 3–5 keV Ar + ions. There is a strong sputtering effect on CuO, which is reduced to Cu 2O. The oxide Cu 2O is much more stable under identical sputter conditions. Even for longer sputter times, Cu 2O is only partially reduced to elemental copper, as can be seen from the Cu(L 3VV) AES spectrum.

The development of sputter-induced pits and pyramids on ion bombarded (11 3 1) surfaces of face centred cubic metal single crystals

It is shown that energetic bombardment of (11 3 1) surfaces of copper single crystals with either Ne +, Ar +, Cu +, Kr + or Xe + ions results in the formation of regular geometric sputter-etch pits from which regular pyramids emerge during the subsequent pit enlargement. Similarly, energetic Ar + bombardment of (11 3 1) surfaces of single crystal nickel, palladium, silver, iridium and gold produces regular pits and pyramids. It is shown that, within certain parameters of ion bombardment, crystallography is the all important condition necessary for production of pits and pyramids. The presence of impurity is unnecessary.

Water adsorption on bromine-covered copper single crystal surfaces

The coadsorption of water with bromine on Cu(110) and Cu(111) has been studied using UPS, LEED, TDS and δφ. The results show that water is more strongly bound to the surface in the vicinity of the bromine than on the clean substrate. This behaviour is interpreted as surface hydration of the partially ionic bromine.Information about the dipole orientation of the solvation water is derived from the observed δφ-values. The LEED studies indicate that island formation with long-range order of the mixed bromine-water layer occurs at fairly low bromine coverages. The experimental results are qualitatively similar on the close-packed (111) and the more open (110) surfac. The relevance of these findings to the electrochemical phenomenon of specific anion adsorption on metal electrodes is briefly discussed.