Pb Layer Research Articles

Effect of Interlayer Thickness of Ion-Plated Pb-Coating on Its Life (SUS440C Substrates)

High-precision ball bearings (SUS440C) used in spacecraft mechanisms that are exposed to deep space vacuum are solid lubricated by thin, adherent Pb ion-plated coatings. The high reliability requirements with long endurance life of these mechanisms solely depend on the tribological aspects of this solid-lubrication coating. Since ion-plated, soft metallic coatings have a graded coating–substrate interface structure, a gradual change in mechanical, chemical and thermal properties is expected across the depth of the coating. This aspect of the interlayer plays a major role in determining the extent of optimum tribological properties of the coating. By improving the interlayer, both in terms of increased thickness and concentration of Pb, a corresponding improvement in the lubricity and endurance life of this Pb ion-plated coating on AISI 440C stainless steel (bearing material) can be assured. For this, a detailed examination of the interlayer of the ion-plated Pb film on the nano-micro level is mandatory. This report is focused on the cross-sectional examination of the interlayer by scanning electron microscopy. SUS440C steel disk specimens having similar properties as the bearing material and with a thin, ion-plated Pb coating processed under two different substrate bias conditions of ion-plating are used. The thickness of the Pb/steel interlayer and the elemental composition are analyzed using SEM and EDS respectively. The endurance life of the coatings is measured by repeated sliding wear tests with a pin-on-disk tester in vacuum. It is confirmed that with an increased thickness of the graded interfacial layer of the Pb ion-plated coating, the coating endurance life is extended remarkably.

High Pressure Deposition of Epitaxial PZT Thin Films on Sr(Nb)TiO3

ABSTRACTEpitaxial thin ferroelectric films of Pb(Zr0.53Ti0.47) (PZT) were successfully grown on Sr(Nb)TiO3(SNTO) single crystal substrates by high-pressure rf sputtering. Pure O2was used as working gas at a pressure above 1 Torr. Deposition temperature was varied from 550°C to 600°C. Under these conditions we were able to deposit films at a rate of 2.7 Å/min. Their crystalline properties, evaluated by Θ/2Θ, ω and φ scans, showed both in-plane and out of plane orientation. Film composition and film-substrate interface characteristics were studied by Rutherford Backscattering Spectroscopy (RBS). For RBS data the composition ratios for the films were calculated having obtained the expected values for a stoichiometric composition. A very thin diffusion layer of Pb at the film-substrate interface was also introduced. However, the deficiency in Pb, which is correlated to the presence of oxygen vacancies, is lower in our films produced at high O2 pressure than those reported for films produced by sputtering at lower pressures. The ferroelectric hysteresis loops measured in the Pt/PZT/SNTO heterostructures show good ferroelectric behavior with remanent polarizations of 12μ Ccm-2and coercive field of 50kVcm-1at 5V. The high-pressured technique representing a useful and capable method capable of obtainingin situepitaxial, fully oxygenated, pyrochlore-free ferroelectric thin film with high quality structural, compositional and dielectric properties, without post deposit treatment.

Anomalous thickness dependence of the Hall effect in ultrathin Pb layers on Si(111)

The magnetoconductive properties of ultrathin Pb films deposited on Si(111) are measured and compared with density-functional electronic band-structure calculations on two-dimensional, free-standing, 1 to 8 monolayers thick Pb(111) slabs. A description with free-standing slabs is possible because it turned out that the Hall coefficient is independent of the substrate and of the crystalline order in the film. We show that the oscillations in sign of the Hall coefficient observed as a function of film thickness can be explained directly from the thickness dependent variations of the electronic band-structure at the Fermi energy.

Lead-based systems as suitable anode materials for Li-ion batteries

Three lead-based materials formed by PbO 2, PbO and Pb as main phases were prepared by following different synthetic procedures and tested as anodic materials in Li-ion batteries by using potentiostatic and galvanostatic methods. While the reduction of Pb(IV) to Pb(II) takes place in a single step, that of Pb(II) to Pb is a complex process involving several steps. Both reduction reactions are irreversible. Lead, whether electrochemically or chemically formed, undergoes an electrochemical reaction with lithium that over the 1.0–0.0 V potential range yields Li x Pb alloys (0≤ x≤4.4). The anodic and cathodic potentiostatic curves exhibit various signals that account for: (i) the formation of different intermediates with variable lithium contents; (ii) the reversibility of the alloying/de-alloying processes; (iii) the increase in complexity of such processes as the oxidation state of lead in them decreases. This results in capacity fading with cycling, particularly in the samples having Pb as the main component. One way of avoiding the capacity loss on cycling involves depositing the active material on lead sheets from spraying suspensions. These coatings exhibit a good capacity retention, which can be ascribed to the formation of a Li x Pb layer at the active material/substrate interface that facilitates electron and ion transfer across the electrode.

Magnetic domains and flux pinning properties of a nanostructured ferromagnet/superconductor bilayer

We have investigated the magnetic and superconducting properties of a nanostructured ferromagnet/superconductor hybrid system, consisting of a Co layer with a square array of rectangular holes (antidots), covered with a thin continuous (nonperforated) superconducting Pb layer. The Co film with an antidot lattice shows a strong in-plane magnetic shape anisotropy determined by the array configuration and the rectangular shape of the antidots. Remanent domain structures in the uncovered Co antidot array are imaged at room temperature by magnetic force microscopy. The superconducting pinning properties of the hybrid ferromagnet/superconductor system are studied for different magnetic states of the Co antidot lattice. We demonstrate that the contribution to the superconducting pinning potential caused by the stray field from the domain walls is stronger than that arising from the periodic modulation due to the underlying antidot lattice.

In Situ TEM Observations on Morphological Instability of Ultrathin Pb Film

Journal Article In Situ TEM Observations on Morphological Instability of Ultrathin Pb Film Get access LH Zhang, LH Zhang Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, P.R. China Search for other works by this author on: Oxford Academic Google Scholar ML Sui, ML Sui Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, P.R. China Search for other works by this author on: Oxford Academic Google Scholar L Zhang, L Zhang Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, P.R. China Search for other works by this author on: Oxford Academic Google Scholar DX Li DX Li Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, P.R. China Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 8, Issue S02, 1 August 2002, Pages 1410–1411, https://doi.org/10.1017/S1431927602103163 Published: 01 August 2002

Properties of ultrathin Pb layers on the Ni(111) face

Properties of ultrathin Pb layers on the Ni(111) face

STM/STS studies of Bi–O layers of Pb doped Bi-2223 superconductors irradiated by 100 MeV oxygen ion

The effect of swift heavy ion (SHI) irradiation on the surface Bi–O layers of polycrystalline Pb doped Bi-2223 superconductors has been studied using Scanning Tunnelling Microscope (STM) technique. The STM images of the unirradiated Pb doped Bi-2223 samples show perfect periodicity of neighbouring atoms whereas the topographs of the irradiated samples reveal atomic displacements and disorder caused by SHI irradiation. The microstructures of these samples are found to be depth dependent. Studies of the electronic structure of the unirradiated and irradiated superconductors have been performed by Scanning Tunneling Spectroscopy (STS). These measurements show setting in of increased non-metallicity on the surface Bi–O layers as a result of irradiation.

Magnetic-domain-controlled vortex pinning in a superconductor/ferromagnet bilayer

Vortex pinning in a type-II superconducting Pb film covering a Co/Pt multilayer with perpendicular magnetic anisotropy is investigated. Different stable magnetic-domain patterns like band and bubble domains can be created in the Co/Pt multilayer, clearly influencing the vortex pinning in the superconducting Pb layer. The most effective pinning is observed for the bubble domain state. We demonstrate that the pinning properties of the superconductor/ferromagnet bilayer can be controlled by tuning the size, density, and magnetization direction of the bubbles.

Effect of the extent and structure of upd adlayers on the reduction of 2-nitroimidazole on Au(111) in acidic solutions

The influence of ad-atom layers of Pb, Tl, Cu, Bi and Ag, deposited in the underpotential region, on the reduction of 2-nitroimidazole on the Au(111) single crystal electrode was studied in aqueous acid solutions. It was found that the kinetics and mechanism of the nitro group reduction depend on the degree of coverage and the superlattice structure of the ad-layers. On Au(111) covered by a low coverage of disordered ad-atoms, the reduction follows an electrocatalytic mechanism associated with a four-electron reduction to 2-hydrohylaminoimidazole. At higher coverage where the ad-atoms form ordered monolayers, the reaction follows an electronation–protonation mechanism associated with a two-electron reduction to a N, N′-dihydroxyamine. This product, rapidly stabilized by two intramolecular hydrogen bonds, cannot be reduced further. Of particular interest is the effect of Cu upd for which a stepwise decrease of the reduction current was observed at potentials closely related to those of the peaks associated with the formation of Cu adlattice structures on Au(111) in the absence of 2-nitroimidazole.

Formula omitted] detectors in experiments at the powerful pulsed accelerators

A possibility of using a thermal neutron detector in the high γ-quantum and bremsstrahlung fields is considered in the paper. The design of the thermal neutron detector consisting of 10 counters filled with 3 He under the pressure of 2 atm and enclosed in the polyethylene moderator is described. The results of measuring the neutron recording efficiency and neutron lifetimes by this detector exposed to a neutron flux from the dt-reaction and from the 252 Cf and Pu–Be sources are reported. The thicknesses of the polyethylene moderator and the Pb layer used for suppression of the background in the fields of powerful electromagnetic radiation are optimized.

Structure of the liquid-vapor interface of a dilute ternary alloy: Pb and Sn in Ga

We report the results of grazing incidence x-ray diffraction and x-ray reflectivity studies of the liquid-vapor interfaces of three dilute ternary alloys, composed of a small constant amount of Pb (0.072 at. %) and a small variable amount of Sn (0.12, 3.4, and 7.7 at. %) dissolved in Ga. The solutes Pb and Sn compete to segregate in the liquid-vapor interfaces of these alloys; in each case, over the temperature range studied (30--120 \ifmmode^\circ\else\textdegree\fi{}C), the composition of the outermost layer of the interface is dominated by excess Pb. In the case of the alloy with Sn concentration of 0.12 at. %, the excess Pb in the liquid-vapor interface forms a crystalline monolayer that melts at 67.8 \ifmmode^\circ\else\textdegree\fi{}C. In the case of the alloy with Sn concentration of 3.4 at. %, the excess Pb in the liquid-vapor interface again forms a crystalline monolayer, but that crystalline monolayer melts at 40.5 \ifmmode^\circ\else\textdegree\fi{}C. In the case of the alloy with Sn concentration of 7.7 at. %, the excess Pb in the liquid-vapor interface forms a two-dimensional liquid over the entire accessible temperature range. When the excess Pb in the liquid-vapor interface forms a two-dimensional crystal, it fully covers the surface of the liquid; at higher temperatures, when the Pb monolayer is liquid, it only partially covers the liquid alloy surface, with the remainder covered by a partial monolayer of liquid Sn. Two-dimensional liquid Pb and two-dimensional liquid Sn appear to be immiscible under the conditions of our experiments. In the case of the sample with the smallest concentration of Sn, the correlation length obtained from the width of the diffraction peak drops almost discontinuously at 67.8 \ifmmode^\circ\else\textdegree\fi{}C to a smaller value. It then further decreases continuously until about 90 \ifmmode^\circ\else\textdegree\fi{}C, thereafter becoming constant. These data suggest the existence of an intermediate disordered phase stable between 67.8 and 90 \ifmmode^\circ\else\textdegree\fi{}C. Our experiments fall short of providing unambiguous evidence for the existence and character of this disordered phase. We speculate that between 67.8 and about 90 \ifmmode^\circ\else\textdegree\fi{}C the Pb monolayer has a hexatic structure and that above 90 \ifmmode^\circ\else\textdegree\fi{}C it is liquid, as is implied by the results of recent simulations of the temperature dependence of the structure of a quasi-two-dimensional layer of Pb.

Tuning the transition temperature of superconducting Ag/Pb films via the proximity effect

We report measurements of the transition temperature ( T C) of superconducting films composed of various combinations of Ag and Pb layers. For samples with good electrical contact between the layers, the measured T C values show reasonable agreement with the Cooper model of the proximity effect. In poorly coupled samples, the normal layers appear to cause little if any suppression of the T C. We present a simple predictive expression for T C as a function of Ag content.

Planar Amperometric Glucose Sensor Based on Glucose Oxidase Immobilized by Chitosan Film on Prussian Blue Layer

A planar amperometric glucose microsensor based on glucose oxidase immobilized by chitosan film on Prussian Blue layer has been developed. The experimental results show that the optimum detection potential is 50 mV (versus Ag/AgCl) and the optimum pH is 6.5. Under the selective conditions the sensor exhibits excellent sensitivity of 98 nA/M and a linear range of 0.1-6.0 mM. The apparent Michanelis-Menten constant of the sensor is 21 mM. The response time is less than 60 seconds. No apparent change in the response to glucose was observed during one month. Foremost, the interference of ascorbic and uric acids can be avoided due to selective permeability of chitosan film and electrocatalysis of PB layer to H2O2. The sensor has been applied to detect glucose in human blood serum.

Clustering in Pb thin films on Si(1 1 1) and Pb-induced Si surface ordering

Pb thin films (10 nm) were deposited from a Knudsen cell on sputter-cleaned Si(1 1 1) substrates under ultrahigh vacuum conditions. Films were deposited at room temperature and subsequently annealed at 300 °C for 30 min. Rutherford backscattering spectrometry and channeling (RBS/C) measurements did not show any channeling in the as-deposited as well as annealed Pb layer. For the annealed sample the spectral broadening in RBS/C spectra occurred due to clustering of Pb, with a simultaneous reduction in the minimum yield from the Si substrate. Prior to Pb deposition the sputter-cleaned Si substrate was annealed at 500 °C, which was insufficient to remove all the damages introduced by Ar + sputtering. Thus the reduction of minimum yield in the substrate for the annealed Pb/Si(1 1 1) system compared to unannealed Pb/Si(1 1 1) may be interpreted as Pb-induced ordering of the Si surface. From the analysis of the step structure observed near the Si edge of the RBS/C spectrum for the annealed sample, it was found that Pb islands (average height ∼35 nm) have been formed on a uniform Pb layer of ∼1 nm thickness. The island formation has been confirmed by atomic force microscopy measurements.

Effects of Pb/Pt Top Electrode on Hydrogen-Induced Degradation in Pb(Zr,Ti)O3

Hydrogen-induced ferroelectric degradation of Pb(Zr,Ti)O3 (PZT) films was studied by measuring the hysteresis curves after hydrogen annealing at various temperatures and times. It was found that hydrogen annealing at temperatures below 100°C resulted in an increase of remanent polarization due to the accumulation of hydrogen ions at the Pt/PZT interface. After hydrogen annealing at 400°C, the ferroelectric characteristics of the Pt/PZT/Pt capacitor deteriorated very rapidly. However, when a thin (50 Å) layer of Pb was deposited on top of the Pt electrode, it was found that the hydrogen-induced ferroelectric degradation was significantly retarded at 400°C. It is presumed that the kinetic path for producing highly reducing hydrogen ions by dissociative adsorption of hydrogen on Pt electrode surfaces was effectively blocked by the poisoning effect of Pb.

The Effect of the Surface Layer on the Dielectric Constant of (Pb, La)TiO3 Thin Films

ABSTRACT:(Pb, La)TiO3 (PLT) ferroelectric thin films are one of the promising candidates for applications in dynamic random memory and pyroelectric detectors, etc. However, the chemical composition in the surface layer of thin films is usually different from that in the “bulk” region of the thin films. For instance, it has been reported that there is Pb, Ti, or La enrichment in the surface layer of the (Pb, La)TiO3 thin films. According to a numerical modeling using effective-medium theory, which was developed in our group, we discussed the effect of the surface layer on the dielectric constant of (Pb, La)TiO3 thin films. The effect of Pb, Ti, or La enrichment in the surface layer on the dielectric constant of PLT thin films was discussed. And a case of the “upgraded” and the “down-graded” thin films was expatiated and discussed.

Pinning of domain walls and flux lines in a nanostructured ferromagnet/superconductor bilayer

We have studied the magnetic and superconducting properties of a nanostructured magnetic/superconducting hybrid system, consisting of a Co layer with a square array of rectangular antidots, covered with a thin 500 Å superconducting Pb layer. The magnetic force microscopy data have revealed that the domain walls are located between neighbouring antidots and are pinned at the antidot corners. The superconducting pinning properties of the hybrid system are studied by means of SQUID magnetisation measurements for different magnetic states of the Co antidot lattice. The results show that the stray field, coming from the domain walls in the antidot array, contributes more to the pinning potential than the periodic modulation of the underlying Co layer. The flux lines seem to be pinned at the domain walls between the antidots. In this way, possible matching effects are lost. The network of domain walls thus creates a new type of an artificial pinning array.

Nuclear-reaction analysis of H at the Pb/Si(111) interface: Monolayer depth distinction and interface structure

Hydrogen atoms buried at the interface between Pb layers and the Si(111) surface were investigated by resonant nuclear reaction analysis (NRA) using ${}^{1}\mathrm{H}{(}^{15}\mathrm{N},\ensuremath{\alpha}\ensuremath{\gamma}{)}^{12}\mathrm{C}$ in grazing incidence geometry. Pb atoms were deposited on the H-terminated Si(111) surface at 110 K, and the H depth was clearly distinguished with a depth scale of one monolayer. The NRA spectrum revealed a monotonous shift to higher energy with increasing Pb coverage indicating H remains at the interface between Pb and the Si substrate. The dependence of the spectral shift on the Pb coverage was found to have an offset corresponding to a depth of about 0.1 nm. This offset suggests a model for the Pb/H/Si(111) interface structure implying that the initial Pb layer resides in the preadsorbed H layer.

Surfactant-induced structures in the heteroepitaxial growth of Co on Cu(111)

The growth of Co on Cu(111) with Pb as a surfactant is found to be accompanied by a considerable surface reconstruction of (4 × 4) symmetry induced by the surfactant. Its crystallography was investigated by quantitative low-energy electron diffraction (LEED) for an initial and later stage of growth with deposition of 1.3 monolayer (ML) and 7 ML Co, respectively. In the low coverage case the surface reconstruction is rather similar to that of Pb/Cu investigated earlier. It extends deep into the substrate with simultaneous minimization of the Pb layer buckling. The structure seems to be controlled by dominating fcc-stacking characteristic of this early stage of growth. With further cobalt deposition the type of reconstruction changes. For the 7 ML Co film it is restricted to the Pb and top Co layer only with the buckling of the surfactant layer considerably increased. We discuss that this may be attributed to the slightly different lattice parameters of Cu and Co, though the influences of the different stacking involved cannot be ruled out. The top film layer is always reconstructed during the whole growth which might be responsible for the easy exchange processes which take place during the growth and are essential for the layer-by-layer growth as found earlier.