Induced magnetism of carbon atoms at the graphene/Ni(111) interface

We report an element-specific investigation of electronic and magnetic properties of the graphene/Ni(111) system. Using magnetic circular dichroism, the occurrence of an induced magnetic moment of the carbon atoms in the graphene layer aligned parallel to the Ni 3d magnetization is observed. We attribute this magnetic moment to the strong hybridization between C $\pi$ and Ni 3d valence band states. The net magnetic moment of carbon in the graphene layer is estimated to be in the range of $0.05-0.1 \mu_B$ per atom.Comment: 10 pages, 3 figure

An Artificially Lattice Mismatched Graphene/Metal Interface: Graphene/Ni/Ir(111)

We report the structural and electronic properties of an artificial graphene/Ni(111) system obtained by the intercalation of a monoatomic layer of Ni in graphene/Ir(111). Upon intercalation, Ni grows epitaxially on Ir(111), resulting in a lattice mismatched graphene/Ni system. By performing Scanning Tunneling Microscopy (STM) measurements and Density Functional Theory (DFT) calculations, we show that the intercalated Ni layer leads to a pronounced buckling of the graphene film. At the same time an enhanced interaction is measured by Angle-Resolved Photo-Emission Spectroscopy (ARPES), showing a clear transition from a nearly-undisturbed to a strongly-hybridized graphene $\pi$-band. A comparison of the intercalation-like graphene system with flat graphene on bulk Ni(111), and mildly corrugated graphene on Ir(111), allows to disentangle the two key properties which lead to the observed increased interaction, namely lattice matching and electronic interaction. Although the latter determines the strength of the hybridization, we find an important influence of the local carbon configuration resulting from the lattice mismatch.Comment: 9 pages, 3 figures, Accepted for publication in Phys. Rev.

Edge States of Monolayer and Bilayer Graphene Nanoribbons

On the basis of tight-binding lattice model, the edge states of monolayer and bilayer graphene nanoribbons (GNRs) with different edge terminations are studied. The effects of edge-hopping modulation, spin-orbital coupling (SOC), and bias voltage on bilayer GNRs are discussed. We observe the following: (i) Some new extra edge states can be created by edge-hopping modulation for monolayer GNRs. (ii) Intralayer Rashba SOC plays a role in depressing the band energy gap $E_g$ opened by intrinsic SOC for both monolayer and bilayer GNRs. An almost linear dependent relation, i.e., $E_g\sim \lambda_R$, is found. (iii) Although the bias voltage favors a bulk energy gap for bilayer graphene without intrinsic SOC, it tends to reduce the gap induced by intrinsic SOC. (iv) The topological phase of the quantum spin Hall effect can be destroyed completely by interlayer Rashba SOC for bilayer GNRs.Comment: 6 pages, 6 figure

Carbon States in Carbon-Encapsulated Nickel Nanoparticles Studied by Means of X-Ray Absorption, Emission, and Photoelectron Spectroscopies

Electronic structure of nickel nanoparticles encapsulated in carbon was characterized by photoelectron, X-ray absorption, and X-ray emission spectroscopies. Experimental spectra are compared with the density of states calculated in the frame of the density functional theory. The carbon shell of Ni nanoparticles has been found to be multilayer graphene with significant (about 6%) amount of Stone--Wales defects. Results of the experiments evidence protection of the metallic nanoparticles from the environmental degradation by providing a barrier against oxidation at least for two years. Exposure in air for 2 years leads to oxidation only of the carbon shell of Ni@C nanoparticles with coverage of functional groups.Comment: 16 pages, 6 figures, accepted in J. Phys. Chem.

Structurally driven one-dimensional electron confinement in sub-5-nm graphene nanowrinkles

Graphene-based carbon materials such as fullerenes, carbon nanotubes, and graphenes have distinct and unique electronic properties that depend on their dimensionality and geometric structures. Graphene wrinkles with pseudo one-dimensional structures have been observed in a graphene sheet. However, their one-dimensional electronic properties have never been observed because of their large widths. Here we report the unique electronic structure of graphene nanowrinkles in a graphene sheet grown on Ni(111), the width of which was small enough to cause one-dimensional electron confinement. Use of spatially resolved, scanning tunnelling spectroscopy revealed bandgap opening and a one-dimensional van Hove singularity in the graphene nanowrinkles, as well as the chemical potential distribution across the graphene nanowrinkles. This observation allows us to realize a metallic-semiconducting-metallic junction in a single graphene sheet. Our demonstration of one-dimensional electron confinement in graphene provides the novel possibility of controlling its electronic properties not by chemical modification but by 'mechanical structuring'.open

Composite fluoropolymer piezoelectric membranes for reconstructive recovery surgery

In the present study, we performed the results of studies on the formation of composite fluoropolymer piezoelectric membranes based on a copolymer of vinylidene fluoride with tetrafluoroethylene (VDF-TeFE) and polyethylpyrrolidone (PEP) by the electrospinning method. Using scanning electron microscopy, the effect of the PEP content on the structure of the formed membranes was studied. The biocompatibility of the obtained membranes was studied by fluorescence microscopy on a model of human skin fibroblasts. The studied samples with a PEP content of 0, 5, and 15% have good adhesive characteristics, preserve the viability and potential of cells to divide, and therefore are most suitable for further use in regenerative medicine

Fluctuations, dissipation and the dynamical Casimir effect

Vacuum fluctuations provide a fundamental source of dissipation for systems coupled to quantum fields by radiation pressure. In the dynamical Casimir effect, accelerating neutral bodies in free space give rise to the emission of real photons while experiencing a damping force which plays the role of a radiation reaction force. Analog models where non-stationary conditions for the electromagnetic field simulate the presence of moving plates are currently under experimental investigation. A dissipative force might also appear in the case of uniform relative motion between two bodies, thus leading to a new kind of friction mechanism without mechanical contact. In this paper, we review recent advances on the dynamical Casimir and non-contact friction effects, highlighting their common physical origin.Comment: 39 pages, 4 figures. Review paper to appear in Lecture Notes in Physics, Volume on Casimir Physics, edited by Diego Dalvit, Peter Milonni, David Roberts, and Felipe da Rosa. Minor changes, a reference adde

Проектирование системы электроснабжения производственной базы по обслуживанию нефтяной промышленности

В выпускной работе рассматривается система электроснабжения производственной базы по обслуживанию нефтяной промышленности. Объектом исследования является прокатно-ремонтный цех производственной базы по обслуживанию нефтяной промышленности. Цель работы: Разработка системы электроснабжения производственной базы по обслуживанию нефтяной промышленности и развитие способности решать технико-экономические вопросы при проектировании систем электроснабжения. В процессе исследования проводились расчеты электрических нагрузок прокатно-ремонтного цеха и предприятия в целом, методами коэффициента расчетной активной мощности и коэффициента спроса соответственно. Произведен выбор низковольтного оборудования прокатно-ремонтного цеха и высоковольтного оборудования главной понизительной подстанции.In the graduate qualification work, the system of power supplying production base for servicing the oil industry is considered. The object of the study is a hire and repair shop of the production base for servicing the oil industry. Purpose of work: development power supplying system production base for servicing the oil industry and development of the ability to solve technical and economic issues in the design of power supplying systems. In the process of the study, calculations were made of the electrical loads of the hire and repair shop and the enterprise as a whole, using the methods of the active power factor and the demand factor, respectively. A choice of low-voltage equipment of the hire and repair shop and high-voltage equipment of the main step-down substation were made

Graphene-passivated nickel as an oxidation-resistant electrode for spintronics.

We report on graphene-passivated ferromagnetic electrodes (GPFE) for spin devices. GPFE are shown to act as spin-polarized oxidation-resistant electrodes. The direct coating of nickel with few layer graphene through a readily scalable chemical vapor deposition (CVD) process allows the preservation of an unoxidized nickel surface upon air exposure. Fabrication and measurement of complete reference tunneling spin valve structures demonstrate that the GPFE is maintained as a spin polarizer and also that the presence of the graphene coating leads to a specific sign reversal of the magneto-resistance. Hence, this work highlights a novel oxidation-resistant spin source which further unlocks low cost wet chemistry processes for spintronics devices.R.S.W. acknowledges funding from EPSRC (Doctoral training award). S.H. acknowledges funding from ERC Grant InsituNANO (Project Reference 279342). P.S. acknowledges the Institut Universitaire de France for junior fellowship support. This research was partially supported by the EU FP7 work programme under Grant GRAFOL (Project Reference 285275).This is the accepted manuscript. The final version is available from ACS at http://pubs.acs.org/doi/abs/10.1021/nn304424x