Nickel Oxide Layer Research Articles

Growth mode of NiO on Cu(111) studied using scanning tunneling microscopy and surface x-ray diffraction

A microscopic description, coherently describing morphological, spectroscopic, and diffraction measurements, of the interface formed by room-temperature deposition of ultrathin nickel oxide layers on a Cu(111) single crystal is presented. The morphology of the Cu(111) substrate surface with respect to the NiO thickness shows a specific hole formation attributed to an oxygen promoted diffusion of Cu on the Cu(111) surface combined with Ni diffusion. It is shown that nickel is dissociated from oxygen in the early stages of growth (below 6 \AA{}) and that nickel diffuses inside the two first sublayers of Cu(111) whereas O atoms form an adsorbed overlayer.

Amperometric determination of sulfide at a pre-oxidised nickel electrode in acidic media.

The electrochemical response of a pre-oxidised nickel electrode to increasing additions of sulfide has been examined and shown to produce a stripping-like voltammetric wave. A mechanism is described based on the formation of nickel sulfide at the electrode surface from a non-electroactive nickel oxide layer. The analytical utility of the approach has been examined and a linear range from 1 to 140 microM and a limit of detection of 0.8 microM is achievable, depending on the accumulation time.

Reactive Solid State Dewetting: Interfacial Cavitation in the System Ag-Ni-O

Micron thick silver films, vapour deposited onto high purity polycrystalline nickel substrates, dewet the substrate after high temperature annealing in oxygen rich atmospheres, while the films remain stable after annealing at the same temperature in a nitrogen atmosphere. Dewetting occurs when a nickel oxide layer is formed at the silver-nickel interface as a consequence of oxygen diffusion through the silver film. The sensitivity of the dewetting process on various parameters such as the annealing: temperature, time and oxygen partial pressure has been determined. Scanning Electron Microscopy (SEM) of cross-sections reveal that the main mechanism of dewetting at short annealing time is the nucleation of cavities at the Ag-NiO interface which grow towards the free surface of the Ag film. They are formed not only at Ag grain boundaries and triple junctions but also in the core of Ag grains. Such cavities do not occur when the Ag film is deposited onto a NiO single crystal. We propose a simple model for the cavitation: a vacancy supersaturation is sustained in Ag, at the Ag-NiO interface, as a result of oxygen consumption by the oxidation reaction. In regions of fast oxidation, the vacancy supersaturation is large enough to promote the nucleation and growth of interfacial cavities. The model qualitatively accounts for all the observed trends; quantitatively, on top of the vacancy supersaturation, extra-contributions to the driving force for cavitation must be invoked.

Structural, Magnetic, and Electronic Properties of the NiO Monolayer Epitaxially Grown on the (001) Ag Surface: An ab Initio Density Functional Study

A periodic slab model consisting of five layers of Ag covered on both sides by NiO monolayers has been adopted to simulate the properties of ultrathin layers of nickel oxide epitaxially grown on silver (001). Different ab initio approaches have been tested including unrestricted Hartree−Fock and a variety of hybrid-exchange density functional Hamiltonians. The hybrid Becke3−Perdew−Wang functional (containing a 20% fraction of Hartree−Fock exchange) has been selected because of its satisfactory performance in describing the experimentally known properties of the two bulk systems, silver and nickel oxide. All calculations have been performed with the CRYSTAL program. In the most stable configuration (O ions directly above Ag atoms, Ni above the hollow sites), the oxide surface is corrugated (0.1 Å) and a small reduction of the work function of the metal is observed (∼0.1 eV). The AFM1 antiferromagnetic structure (alternating rows of nickel ions with opposite spin along the [11] direction) is the most stable one both in the isolated and in the supported monolayer. The Ni−Ni superexchange constant (J2) is appreciably increased (30%) by the presence of the Ag substrate. In conclusion, the presence of the metallic substrate has been found to influence the structural, electronic, and magnetic properties of the overlayer but only to a limited extent.

Electrochemical Oxidation of CO on Pt and Ni Point Electrodes in Contact with an Yttria-Stabilized Zirconia Electrolyte: II. Steady-State and Impedance Measurements

Electrochemical measurements were performed with Pt and Ni electrodes forming an approximate (macroscopic) point contact with a solid electrolyte, for mixtures of in the temperature range 827 to 950°C and 775 to 924°C, respectively. Steady-state current and impedance spectra vs. overpotential under the different experimental conditions were compared with the theoretical models derived in Part I of this paper. A low-frequency inductive loop in the fourth quadrant of the impedance spectra appearing under certain experimental conditions is consistent with a model for a reaction mechanism involving two adsorbed intermediates. At high anodic overpotentials, the data for Ni electrodes are consistent with the formation of an insulating layer of nickel oxide (NiO) in the electrode/electrolyte interface. Irrespective of the experimental conditions, no effects of diffusion limitations were seen in the impedance spectra. The electrode metal plays a significant role in the overall reaction. For Ni, the results indicate a lower specific electrocatalytic activity for than for the reaction. © 2002 The Electrochemical Society. All rights reserved.

Enhanced hole injections in organic light-emitting devices by depositing nickel oxide on indium tin oxide anode

An ultrathin layer of nickel oxide (NiO) was deposited on the indium tin oxide (ITO) anode to enhance the hole injections in organic light-emitting diode (OLED) devices. A very low turn-on voltage (3 V) was actually observed for the device with NiO on ITO. The enhancement of hole injections by depositing NiO on the ITO anode was further verified by the hole-only devices. The excellent hole-injection ability of NiO was also demonstrated by devising a device with patterned NiO on the ITO anode. Our results suggest that the NiO/ITO anode is an excellent choice to enhance hole injections of OLED devices.

Effects of Hydrogen Implantation on the Structural and Electrical Properties of Nickel Silicide

The effects of hydrogen implantation on the structural and electrical properties of nickel silicide have been investigated. Ni films (30 nm) are electron-beam-evaporated on Si substrates, after which plasma immersion ion implantation is used to introduce hydrogen ions into the Ni films at an energy of 350 eV to a dose of For nickel silicidation reactions, rapid thermal annealing is carried out in the range of 400-750°C for 30 s in a nitrogen atmosphere. It is shown that the implanted samples produce lower sheet resistances than the unimplanted samples across the whole annealing temperature range. X-ray diffraction results show that, regardless of the hydrogen implantation, NiSi is transformed into at temperatures in excess of 700°C. X-ray photoemission spectroscopy results show that the hydrogen implantation plays a role in reducing the nickel oxide layer. Compared to the unimplanted samples, the implanted samples exhibit better surfaces and uniform NiSi/Si interface morphologies. Transmission electron microscopy results show that the grain sizes of the implanted sample are smaller than those of the unimplanted sample. It is further shown that the implanted samples are thermally more stable than the unimplanted samples, which is attributed to the difference in the grain sizes of the nickel silicide films. © 2002 The Electrochemical Society. All rights reserved.

Anodization of electroformed nickel for the manufacture of compact disc stampers

Compact discs are manufactured using electroformed nickel stampers. The process of making stampers involves the anodization of the metal works in alkaline solutions. During the anodization process, a layer of nickel oxide is formed on the surface of the electroformed metal works that subsequently is removed by the next process. This process may be repeated several times for each metal work in the course of CD manufacturing. In the present work, the effect of the growth and removal of NiO film on the quality of the stampers has been investigated. This work shows that although the nickel oxide layer formed under normal conditions of the anodizing bath is extremely thin, the quality of the stampers can be affected, by repeating the standard anodizing process for a number of times or by prolonged and vigorous anodization. A model has been presented for NiO formation and safe conditions for anodization have been proposed. Compact disc (CD-CDROM-DVD) manufacture involves a complex series of processes including engraving the digital data onto a glass coated with photoresist using a laser beam, in the form of little pits and lands. The dimensions of these pits and lands are critical and should be kept within a very narrow range. Both pits and lands vary in length but their depths and widths remain constant. In fact, in a typical compact disk there are pits and lands with 9 different lengths, conventionally referred to as 3T to 11T. The depth of the pits are adjusted to be a quarter of the playback laser’s wavelength, which works out to be about 110 to 113 nm. The data image face of the glass master is then sputtered with a thin layer of nickel/vanadium allowing the subsequent electroforming process. The next process in CD manufacture is the transfer the image from the so-called “glass master” onto a metal work, which has a hardness that is suitable for usage as a stamper in molding machines. The stamper, now having the negative image of the data is placed in an injection molding machine, pressing a molten transparent polycarbonate against it, replicating the original positive image. The polycarbonate disc is then covered with lacquer and together with artwork it forms the familiar CD/CDROM/ DVD shape. The electroforming process is, however, far from a straightforward process, involving several intermediate stages, including the anodization process. There are two reasons for anodizing the Ni metal works:

Atomic Layer Deposition of Nickel by the Reduction of Preformed Nickel Oxide

A thin film of elementary nickel was formed by atomic layer deposition (ALD). The deposition cycle consisted of two consecutive chemical reaction steps: an oxidizing step and a reducing step. An atomic layer of nickel oxide was made by sequentially supplying bis(cyclopentadienyl)-nickel as a nickel precursor and water as an oxidation agent; the preformed atomic layer of nickel oxide was then reduced to elementary nickel metal by exposure to hydrogen radical at a deposition temperature of 165°C. Auger electron spectroscopy analysis detected negligible oxygen content in the grown films, indicating that the hydrogen radical had completely reduced the nickel oxide to a metallic thin film. In addition, carbon impurities in the film dropped from 16 atom % to less than 5 atom % during the reduction reaction. The proposed two-step ALD method for elementary metals was successful in forming continuous and conformal nickel thin films. These nickel films formed an effective glue layer between chemical vapor deposited copper and a diffusion barrier layer of TiN. The adhesion of a 1 μm thick copper film to a 15 nm thick nickel glue layer over a TiN barrier film was excellent, with no failures occurring during adhesive tape peel tests. © 2002 The Electrochemical Society. All rights reserved.

YBCO coated nickel-based tapes with various buffer layers

Biaxially textured YBa 2 Cu 3 O 7 (YBCO) thin films, yttria stabilized zirconia (YSZ) and yttria (Y 2 O 3 ), CeO 2 buffer layers were grown in situ on NiO/Ni based substrates by Pulsed Injection MOCVD (PICVD) using monoglyme solutions of β-diketonates (Cu(thd) 2 , Ba(thd) 2 , Y(thd) 3 , Ce (thd) 2 , Zr(thd) 4 ). High quality textured nickel oxide layers have been prepared by SOE (Surface Oxydation Epitaxy) following an optimized recrystallisation-oxidation process.Thin YSZ/Y 2 O 3 biaxially textured buffer layers (thickness 200nm/200 nm) were deposited in a wide range of temperature (from 600°C to 800°C). Subsequent YBCO layers (thickness 750nm) on Ni/NiO/YSZ/Y 2 O 3 were grown epitaxially (ω-scan of YBCO FWMH=5°) and exhibited critical current densities Jc ≥3.10 5 A/cm 2 with a critical temperature Tc=90K and ΔTc ≤ 1 K. The best results were obtained for deposition temperatures of 600°C for YSZ, 675°C for Y 2 O 3 and 800°C for YBCO.

Oxygen Plasma Preparation of Nickel Oxide Layers

Nickel oxide thin films form and grow when Nickel foils are exposed to an inductively coupled low pressure oxygen plasma. The resulting oxide (NiO) is identified by near-grazing X-ray diffraction and by FTIR specular reflectance spectroscopy methods. The thickness of the NiO layer increases with exposure time.

Kinetics and mechanisms of reactive solid state dewetting in the system Ag–Ni–O

Thick silver films vapour deposited under ultra high vacuum onto high purity nickel foils, dewet the substrate when annealed at high temperature in air. No hole is observed in the silver film after an annealing at the same temperature in a pure argon atmosphere. SEM observations of the film surface and of cross-sections reveal that dewetting occurs when a nickel oxide layer is formed at the silver–nickel interface as a result of oxygen diffusion through the silver film [Phil. Mag. Lett. 80(2000)33]. The kinetics of the phenomenon has been studied for films 1.8 microns thick annealed at 1123 K. Four dewetting mechanisms have been identified and are described. In the case of short heat treatments (1 h at 1123 K in air) the main dewetting mechanism is observed to be the condensation at the silver–nickel oxide interface of vacancies into voids which grow towards the free surface of the silver film.

Tris(3-mercaptopropyl)-N-glycylaminomethane as a new linker to bridge antibody with metal particles for biological cell separations.

Conjugates of nickel beads with CD8 and anti-red blood cell KC16 antibody were prepared by using the aminotrithiolate "spider" ligand, tris(3-mercaptopropyl)-N-glycylaminomethane, in its new function as a linker between the surface of nickel beads and antibody via activation of spider ligand attached to nickel beads with the common, heterobifunctional cross-linker, sulfosuccinimidyl 4-(N-maleimidomethyl)cyclohexane-1-carboxylate (sulfo-SMCC). Raw nickel beads were cleaned by either mild sonication in a bath or by stronger probe sonication to remove surface nickel oxide layers, before attachment of the spider ligand. Scanning electron micrographs of the nickel beads before and after probe sonication showed a marked change from a corrugated to a smooth bead surface. Analyses of the supernatants of conjugation mixtures for antibody gave surface densities of 2.5-5.2 mg/m(2) for CD8 and 0.6-12 mg/m(2) for KC16 antibody runs. The antibody-spider-nickel bead conjugates were used in magnetic bead depletions of targeted CD8+ lymphocytes or red blood cells (rbcs) in whole blood of normal donors. For CD8 cell depletions, the undepleted controls and supernatants of depleted samples were analyzed for CD8/CD4 cell populations by flow cytometry with appropriate fluorescent antibody markers. Enumeration of red blood cells, white blood cells (wbcs), and platelets (plts) in undepleted controls and supernatants of depleted samples were carried out on appropriate hematology counters. Whole blood titer results with various lots of either CD8-spider-nickel or KC16-spider-nickel bead conjugates showed varying degrees of depletion ability as indicated by bead-to-cell ratios of 2-32 for CD8 beads and by rbc-to-bead ratios of 1.2-10 for KC16 beads. Moreover, varying degrees of specificity of CD8 beads for CD8+ cells over CD4+ cells and of KC16 beads for rbcs over white blood cells and platelets were observed from the normalized nontargeted cell population figures in undepleted controls versus supernatants of depleted samples.

Reduction of oxidized nickel surfaces

The behavior of oxidized nickel surfaces was studied with X-ray photoelectron spectroscopy (XPS) during a heating process. Different surface states were prepared by oxidizing the surfaces of a nickel single crystal with (111) orientation, and polycrystalline nickel foils in oxygen or water vapor. A nickel oxide layer of thickness 2 ML was formed during the oxygen exposure. Oxidation in water vapor at 30 mbar yielded an additional nickel hydroxide layer. During the heating experiments (300–900 K), the surfaces of the oxidized samples were reduced to metallic nickel. The reduction process of the nickel surfaces oxidized in oxygen was supported by hydrogen exposure (10 −6 mbar). At low hydrogen pressures the reduction of the polycrystalline nickel surface took place at temperatures lower than the reduction of the oxidized single crystal surface. In experiments at 10 −6 mbar hydrogen no significant difference could be observed between the two samples. Defecting the single crystal surface by ion etching before oxidizing yielded no change in reduction behavior. On the surfaces oxidized in water vapor, the nickel hydroxide was reduced at low temperatures in a first step whereas the nickel oxide remained unreduced. The reduction of the remaining nickel oxide took place at the same temperatures as the reduction of the surfaces oxidized in oxygen.

Reactive solid-state dewetting

High-temperature annealing in air of thick crystalline silver films deposited on high-purity nickel foils promotes solid-state dewetting, whereas no hole through the film is produced when annealing under high purity argon. Scanning electron microscopy observations of the film surface and of cross-sections reveal that dewetting occurs only if a nickel oxide layer forms at the silver-nickel interface, as a result of oxygen diffusion through the silver film. The main dewetting mechanism over short times (1h 1120K in air) is observed to be the condensation, at the silver-nickel oxide interface, of vacancies into voids which grow towards the free surface of the silver film.

XPS study of the adsorption of NH3 on nickel oxide on Ni(111)

The aim of the present work was to investigate the initial stages of NH3 interaction with nickel oxide layers formed on well-defined Ni(111) surfaces. The selected technique was x-ray photoelectron spectroscopy. Ammonia adsorption was performed at 10−7 mbar and room temperature in a preparation chamber attached to the analysis chamber. After each adsorption, the N 1s core level was analysed and its intensity was plotted as a function of exposure (at the same pressure) to obtain the adsorption kinetnetics. The XPS peak shapes and the chemical shifts were related to the nature of the adsorption products. In our experimental conditions, we observed that the more reactive initial surface was the one covered by the O-adsorbed phase corresponding to the precursor state of the NiO formation. The NiO alone does not exhibit significant reactivity, whereas a mixture of NiO and the O-adsorbed phase shows a similar behaviour to that of the pure O-adsorbed phase. From the first adsorption until the last one, two nitrogen adspecies were detected: one with an N 1s binding energy (BE) of 397.8 eV and the other at 399.7 eV. The data indicate that the surface reactivity is structure-sensitive for the NiO layer and the mechanisms of adsorption seem to involve NH3 dissociation into NHx adspecies, along with OH formation. Copyright © 2000 John Wiley & Sons, Ltd.

Phase Formation Studies and Structural Properties of Laser Ablated (Pb,La)(Zr, Ti)O3-Thin-Films on Stainless Steel

AbstractIt is shown that high-quality La-doped PZT-films, (Pb,La)(Zr,Ti)O3, can be deposited by pulsed laser deposition (PLD) directly onto stainless steel substrates resulting in a very simple bicomponental system with high potential for sensor applications. This is an astonishing result, since there is quite a substantial lattice mismatch between the substrate and the PZT-film. Careful investigations revealed the existence of a thin oriented nickeloxide layer at the surface of the stainless steel. The formation of this interface layer leads to a reduction of the lattice mismatch thus affecting the subsequent phase formation of the perovskite PZT. The interface was examined by RBS, XRD, TEM / X-TEM studies and SIMS depth profiling. The phase formation and stoichiometry of the PZT films were investigated by XRD and EDX and their microstructure and texture by SEM and XRD pole figure measurements.

Formation of Nickel Ferrite Films by Solid-State Reaction

Nickel ferrite (NiFe2O4) thin films are of potential interest for magnetic applications. In the present study, the production of NiFe2O4 by solid-state reaction between thin films of hematite (α-Fe2O3) and nickel oxide (NiO) on (0001) sapphire (α-Fe2O3) substrates has been examined. The NiFe2O4 thin films were prepared by two different methods. In the first case the NiFe2O4film was grown in situ in the deposition system, while in the second case the NiFe2O4 film was formed ex situ by reacting at elevated temperatures in air. These two methods of reaction lead to interesting morphological differences in the ferrite layers.Epilayers of α-Fe2O3 followed by NiO were deposited onto (0001) α-Al2O3 by pulsed-laser deposition (PLD) in 6 mTorr O2. NiFe2O4 films were obtained by reacting the starting films in two different ways: in situ (during film growth) and ex situ.. In both cases, the α-Fe2O3 films were grown under the same conditions while those for the deposition of the NiO layers were different.

Spatially resolved concentration measurements during cathodic alloy deposition in microstructures

Local concentration distributions within microstructures, alloy composition, the effects of side reactions and the influence of convection on electrodeposition in microstructures were measured. Since technically relevant microstructures have complex geometries, experiments involving locally resolved measurements using freely positionable microelectrodes are necessary. The SLCP method is based upon chronoamperometry and was used for simultaneous measurement of absolute concentration values of copper and nickel. In this way concentration profiles were measured as c( xy), c( x) and c( z). In a trench microstructure, concentration distribution was investigated as a function of the aspect ratio in unstirred solution and under convectional influence. In direct comparison to the conditions in the unstirred electrolyte, a notable intrusion of the flow is observed at aspect ratios ≤ 1. At a higher aspect ratio the concentration distribution is uniform. With higher aspect ratios ( eg 1.5) the effects of side reactions on the metal deposition increase. During CuNi alloy deposition the formation of nickel oxide and nickel hydroxide layers can be detected.

Electrochemical oxidation of isobutanol to isobutyric acid at nickel oxide electrode : improvement of the anode stability

Electrooxidation processes using nickel oxide anodes in alkaline electrolyte offer good alternatives to the chemical processes used for the oxidation of alcohols. However, they suffer from the low stability of the electrodeposited layer of nickel oxide, resulting in poor current efficiency. This requires periodic reactivation of the anode. In the present work, different parameters governing the stability of the nickel oxide layer have been identified and their influence on the current efficiency for oxidation has been investigated using oxidation of isobutanol (2-methyl-1-propanol) to isobutyric acid (2-methylpropionic acid) as a model system. Alternative anode activation procedures have been studied. The procedures employed resulted in a five fold increase in the anode stability over earlier reported procedures for anode activation and electrolysis.