The Experts below are selected from a list of 46284 Experts worldwide ranked by ideXlab platform
Jurgen Kirschner - One of the best experts on this subject based on the ideXlab platform.
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new insights into nanomagnetism spin polarized Scanning Tunneling Microscopy and spectroscopy studies
Proceedings of SPIE, 2011Co-Authors: Hirofumi Oka, Guillemin Rodary, Sebastian Wedekind, P A Ignatiev, L Niebergall, V S Stepanyuk, D Sander, Jurgen KirschnerAbstract:We perform low-temperature spin-polarized Scanning Tunneling Microscopy (SP-STM) and spectroscopy measurements in magnetic fields to gain new insights into nanomagnetism. We use the magnetic field to change and control magnetizations of a sample and a magnetic tip, and measure the magnetic hysteresis loops of individual Co nano-islands on Cu(111). We also exploit the high spatial resolution of SP-STM in magnetic fields to measure maps of the differential conductance within a single Co nano-island. In connection with ab initio calculations, we find that the spin polarization is not homogeneous but spatially modulated within the nano-island. We ascribe the spatial variation of the spin polarization to spin-dependent electron confinement within the Co nano-island.
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a combined magnetic force and spin polarized Scanning Tunneling Microscopy study of the closure domain pattern of co 0001
Materials Science and Engineering B-advanced Functional Solid-state Materials, 2001Co-Authors: H F Ding, Wulf Wulfhekel, C Chen, J Barthel, Jurgen KirschnerAbstract:The complex fractal closure domain pattern of bulk Co(0001) is investigated using standard magnetic force Microscopy in air and spin-polarized Scanning Tunneling Microscopy in ultra high vacuum. The advantages as well as the limits of both methods based on the fundamentally different contrast mechanisms are illustrated. Using spin-polarized Scanning Tunneling Microscopy, further insight in the fine structure of the magnetic configuration of Co(0001) is gained.
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fast interdiffusion in thin films Scanning Tunneling Microscopy determination of surface diffusion through microscopic pinholes
Physical Review B, 1993Co-Authors: A K Schmid, D Atlan, H Itoh, B Heinrich, T Ichinokawa, Jurgen KirschnerAbstract:Diffusion of substrate material to the surface of some epitaxial thin-film systems has been reported to occur very rapidly, even at temperatures below 40% of the melting points of film and substrate, where bulk interdiffusion should be negligible. In situ Scanning Tunneling Microscopy reveals that the Cu diffusion through ultrathin Co films grown under ultrahigh vacuum onto Cu(100) substrates occurs via a surface diffusion process, not via bulk interdiffusion. During annealing, pores nucleate in weak points of the films, e.g., near step bands of the substrate. As Cu diffuses from the substrate through the pores to the top of the film, pits of up to several tens of nm linear dimensions are formed
Tomihiro Hashizume - One of the best experts on this subject based on the ideXlab platform.
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moire image patterns on double walled carbon nanotubes observed by Scanning Tunneling Microscopy
Physical Review B, 2009Co-Authors: Nobuyuki Fukui, Tomihiro Hashizume, Yuji Suwa, Hiromichi Yoshida, Toshiki Sugai, Seiji Heike, Masaaki Fujimori, Yasuhiko TeradaAbstract:Long-range quasiperiodic patterns are found in Scanning Tunneling Microscopy (STM) images of double-walled carbon nanotubes (DWNTs) on top of the atomic images of six-membered carbon rings of the outer tubes. By comparing the results of first-principles calculations on model DWNTs, we conclude that they are moir\'e patterns showing local modulations of electronic states due to the interlayer interactions between the outer and inner tubes. We also demonstrate that these moir\'e patterns can be used to assign the chiral vector of the inner tube of a DWNT which is usually inaccessible by STM.
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field ion Scanning Tunneling Microscopy study of c60 on the si 100 surface
Japanese Journal of Applied Physics, 1992Co-Authors: Tomihiro Hashizume, X D Wang, Yuichiro Nishina, Hisanori Shinohara, Yahachi Saito, Young Kuk, Toshio SakuraiAbstract:Field ion-Scanning Tunneling Microscopy was employed to study the monolayer and multilayer adsorption behaviors of the C60 fullerene on the Si(100)2×1 surface. The C60 molecules reside stably in the trough at room temperature without rotation, encompassing the 8 neighbouring dimer-forming surface Si atoms with the nearest neighbour distance of 12 A. For the first and second layers, only local ordering of square and quasi-hexagonal patterns was observed. The orderly Stranski-Krastanov mode island formation with the hexagonal packing was observed above the third layer with its lattice constant of 10.4 A.
Gerhard Meyer - One of the best experts on this subject based on the ideXlab platform.
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different tips for high resolution atomic force Microscopy and Scanning Tunneling Microscopy of single molecules
Applied Physics Letters, 2013Co-Authors: Fabian Mohn, Bruno Schuler, Leo Gross, Gerhard MeyerAbstract:We explore different tip functionalizations for atomic force Microscopy (AFM), Scanning Tunneling Microscopy (STM), and Kelvin probe force Microscopy (KPFM) of organic molecules on thin insulating films. We describe in detail how tips terminated with single Br and Xe atoms can be created. The performance of these tips in AFM, STM, and KPFM imaging of single molecules is compared to other tip terminations, and the advantages and disadvantages of the different tips are discussed. The Br tip was found to be particularly useful for AFM and lateral manipulation, whereas the Xe tip excelled in STM and KPFM.
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molecules on insulating films Scanning Tunneling Microscopy imaging of individual molecular orbitals
Physical Review Letters, 2005Co-Authors: Jascha Repp, Andre Gourdon, Sladjana Stojkovic, Gerhard Meyer, Christian JoachimAbstract:Ultrathin insulating NaCl films have been employed to decouple individual pentacene molecules electronically from the metallic substrate. This allows the inherent electronic structure of the free molecule to be preserved and studied by means of low-temperature Scanning-Tunneling Microscopy. Thereby direct images of the unperturbed molecular orbitals of the individual pentacene molecules are obtained. Elastic scattering quantum chemistry calculations substantiate the experimental findings.
Flemming Besenbacher - One of the best experts on this subject based on the ideXlab platform.
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mos2 nanoparticle morphologies in hydrodesulfurization catalysis studied by Scanning Tunneling Microscopy
Journal of Catalysis, 2013Co-Authors: Alex S Walton, Jeppe V Lauritsen, H Topsoe, Flemming BesenbacherAbstract:Information on the morphology and edge structures of single-layer MoS2 and promoted CoMoS nanoparticles is essential in order to understand and accurately model the activity in hydrodesulfurization catalysis. Only the edge sites in single-layer MoS2 nanoparticles are known to be active in catalysis, but since different edge structures are possible, the activity and selectivity may depend critically on the exact morphology. From atom-resolved Scanning Tunneling Microscopy (STM) experiments, we provide here a general overview of the atomic-scale effect of sulfo-reductive atmospheres, sulfiding agents, promoter atoms, and support type on the equilibrium morphology of single-layer MoS2. Overall strong morphology variations are seen. These variations are interpreted in the framework of the Wulff construction as differences in edge energies induced by the conditions of the experiment. The results highlight the STM as an increasingly important experimental technique to investigate the atomic-scale structure of catalytically active nanoparticles in general and as one of the only tools, which can address single atom defects and single adsorption events on the atomic-scale.
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adsorbate induced alloy phase separation a direct view by high pressure Scanning Tunneling Microscopy
Physical Review Letters, 2005Co-Authors: Ebbe K Vestergaard, Ronnie T Vang, Jan Knudsen, T M Pedersen, Toshu An, Erik Laegsgaard, I Stensgaard, Bjork Hammer, Flemming BesenbacherAbstract:: The influence of high pressures of carbon monoxide (CO) on the stability of a Au/Ni(111) surface alloy has been studied by high-pressure Scanning Tunneling Microscopy. We show that CO induces a phase separation of the surface alloy at high pressures, and by means of time-lapsed STM movies we find that Ni atoms are removed from the surface layer during the process. Density functional theory calculations reveal the thermodynamic driving force for the phase separation to be the Au-induced compression of the CO overlayer with a resulting CO-CO repulsion. Furthermore, the atomistic mechanism of the process is shown to be kink-site carbonyl formation and evaporation which is found to be enhanced by the presence of Au.
George W Flynn - One of the best experts on this subject based on the ideXlab platform.
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Scanning Tunneling Microscopy and x ray photoelectron spectroscopy studies of graphene films prepared by sonication assisted dispersion
ACS Nano, 2011Co-Authors: Elena Y Polyakova, Kwang Taeg Rim, Daejin Eom, Keith Douglass, R L Opila, Tony F Heinz, Andrew V Teplyakov, George W FlynnAbstract:We describe Scanning Tunneling Microscopy and X-ray photoelectron spectroscopy studies of graphene films produced by sonication-assisted dispersion. Defects in these samples are not randomly distributed, and the graphene films exhibit a “patchwork” structure where unperturbed graphene areas are adjacent to heavily functionalized ones. Adjacent graphene layers are likely in poor mechanical contact due to adventitious species trapped between the carbon sheets of the sample.
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high resolution Scanning Tunneling Microscopy imaging of mesoscopic graphene sheets on an insulating surface
Proceedings of the National Academy of Sciences of the United States of America, 2007Co-Authors: Elena Stolyarova, Kwang Taeg Rim, Tony F Heinz, S Ryu, Janina Maultzsch, Philip Kim, Louis E Brus, Mark S Hybertsen, George W FlynnAbstract:We present Scanning Tunneling Microscopy (STM) images of single-layer graphene crystals examined under ultrahigh vacuum conditions. The samples, with lateral dimensions on the micrometer scale, were prepared on a silicon dioxide surface by direct exfoliation of crystalline graphite. The single-layer films were identified by using Raman spectroscopy. Topographic images of single-layer samples display the honeycomb structure expected for the full hexagonal symmetry of an isolated graphene monolayer. The absence of observable defects in the STM images is indicative of the high quality of these films. Crystals composed of a few layers of graphene also were examined. They exhibited dramatically different STM topography, displaying the reduced threefold symmetry characteristic of the surface of bulk graphite.
