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Scanning probe microscopy and spectroscopy of graphene on metals  [PDF]
Yuriy Dedkov,Elena Voloshina,Mikhail Fonin
Physics , 2015, DOI: 10.1002/pssb.201451466
Abstract: Graphene, a two-dimensional (2D) material with unique electronic properties, appears to be an ideal object for the application of surface-science methods. Among them, a family of scanning probe microscopy methods (STM, AFM, KPFM) and the corresponding spectroscopy add-ons provide information about the structure and electronic properties of graphene on the local scale (from inline imagem to atoms). This review focuses on the recent applications of these microscopic/spectroscopic methods for the investigation of graphene on metals (interfaces, intercalation-like systems, graphene nanoribbons, and quantum dots, etc.). It is shown that very important information about interaction strength at the graphene/metal interfaces as well as about modification of the electronic spectrum of graphene at the Fermi level can be obtained on the local scale. The combination of these results with those obtained by other methods and comparison with recent theoretical data demonstrate the power of this approach for the investigation of the graphene-based systems.
Scanning probe microscopy imaging of metallic nanocontacts  [PDF]
D. St?ffler,S. Fostner,P. Grütter,R. Hoffmann-Vogel
Physics , 2011, DOI: 10.1103/PhysRevB.85.033404
Abstract: We show scanning probe microscopy measurements of metallic nanocontacts between controlled electromigration cycles. The nanowires used for the thinning process are fabricated by shadow evaporation. The highest resolution obtained using scanning force microscopy is about 3 nm. During the first few electromigration cycles the overall slit structure of the nanocontact is formed. The slit first passes along grain boundaries and then at a later stage vertically splits grains in the course of consuming them. We find that first the whole wire is heated and later during the thinning process as the slit forms the current runs over several smaller contacts which needs less power.
Ultra High Thermal Resolution Scanning Probe Microscopy via Carbon Nanotube Tipped Thermal Probes  [PDF]
Peter D. Tovee,Manuel E. Pumarol,Mark C. Rosamond,Robert Jones,Michael C. Petty,Dagou A. Zeze,Oleg V. Kolosov
Physics , 2013,
Abstract: We present a new concept of scanning thermal nanoprobe that utilizes the extreme thermal conductance of a carbon nanotube (CNT) to channel heat between the probe and the sample. The integration of CNT in scanning thermal microscopy (SThM) overcomes the main drawbacks of standard SThM probes, where the low thermal conductance of the apex SThM probe is the main limiting factor. The integration of CNT (CNT- SThM) extends SThM sensitivity to thermal transport measurement in higher thermal conductivity materials such as metals, semiconductors and ceramics, while also improving the spatial resolution. Investigation of thermal transport in ultra large scale integration (ULSI) interconnects, using CNT- SThM probe, showed fine details of heat transport in ceramic layer, vital for mitigating electromigration in ULSI metallic current leads. For a few layer graphene, the heat transport sensitivity and spatial resolution of the CNT-SThM probe demonstrated significantly superior thermal resolution compared to that of standard SThM probes achieving 20-30 nm topography and ~30 nm thermal spatial resolution compared to 50-100 nm for standard SThM probes. The outstanding axial thermal conductivity, high aspect ratio and robustness of CNTs can make CNT-SThM the perfect thermal probe for the measurement of nanoscale thermophysical properties and an excellent candidate for the next generation of thermal microscopes.
Implementation of atomically defined Field Ion Microscopy tips in Scanning Probe Microscopy  [PDF]
William Paul,Yoichi Miyahara,Peter Grütter
Physics , 2012, DOI: 10.1088/0957-4484/23/33/335702
Abstract: The Field Ion Microscope (FIM) can be used to characterize the atomic configuration of the apex of sharp tips. These tips are well suited for Scanning Probe Microscopy (SPM) since they predetermine SPM resolution and electronic structure for spectroscopy. A protocol is proposed to preserve the atomic structure of the tip apex from etching due to gas impurities during the transfer period from FIM to SPM, and estimations are made regarding the time limitations of such an experiment due to contamination by ultra-high vacuum (UHV) rest gases. While avoiding any current setpoint overshoot to preserve the tip integrity, we present results from approaches of atomically defined tungsten tips to the tunneling regime with Au(111), HOPG, and Si(111) surfaces at room temperature. We conclude from these experiments that adatom mobility and physisorbed gas on the sample surface limit the choice of surfaces for which the tip integrity is preserved in tunneling experiments at room temperature. The atomic structure of FIM tip apices is unchanged only after tunneling to the highly reactive Si(111) surface.
Dynamic scanning probe microscopy of adsorbed molecules on graphite  [PDF]
N. Berdunov,A. J. Pollard,P. H. Beton
Physics , 2008, DOI: 10.1063/1.3075054
Abstract: We have used a combined dynamic scanning tunneling and atomic force microscope to study the organisation of weakly bound adsorbed molecules on a graphite substrate. Specifically we have acquired images of islands of the perylene derivative molecules. These weakly bound molecules may be imaged in dynamic STM, in which the probe is oscillated above the surface. We show that molecular resolution may be readily attained and that a similar mode of imaging may be realised using conventional STM arrangement. We also show, using tunnelling spectroscopy, the presence of an energy gap for the adsorbed molecules confirming a weak molecule-substrate interaction.
Multichannel scanning probe microscopy and spectroscopy of graphene moire structures  [PDF]
Yu. S. Dedkov,E. N. Voloshina
Physics , 2013, DOI: 10.1039/C3CP54541E
Abstract: The graphene moire structures on metals, as they demonstrate both long (moire) and short (atomic) scale ordered structures, are the ideal systems for the application of scanning probe methods. Here we present the complex studies of the graphene/Ir(111) system by means of 3D scanning tunnelling and atomic force microscopy/spectroscopy as well as Kelvin-probe force microscopy. All results clearly demonstrate a variation of the moire and atomic scale contrasts as a function of the bias voltage as well as the distance between the scanning probe and the sample, allowing to discriminate between topographic and electronic contributions in the imaging of a graphene layer on metals. The presented results are accompanied by the state-of-the-art density functional theory calculations demonstrating the excellent agreement between theoretical and experimental data.
Electromechanical Detection in Scanning Probe Microscopy: Tip Models and Materials Contrast  [PDF]
Eugene A. Eliseev,Sergei V. Kalinin,Stephen Jesse,Svetlana L. Bravina,Anna N. Morozovska
Physics , 2006, DOI: 10.1063/1.2749463
Abstract: The rapid development of nanoscience and nanotechnology in the last two decades was stimulated by the emergence of scanning probe microscopy (SPM) techniques capable of accessing local material properties, including transport, mechanical, and electromechanical behavior on the nanoscale. Here, we analyze the general principles of electromechanical probing by piezoresponse force microscopy (PFM), a scanning probe technique applicable to a broad range of piezoelectric and ferroelectric materials. The physics of image formation in PFM is compared to Scanning Tunneling Microscopy and Atomic Force Microscopy in terms of the tensorial nature of excitation and the detection signals and signal dependence on the tip-surface contact area. It is shown that its insensitivity to contact area, capability for vector detection, and strong orientational dependence render this technique a distinct class of SPM. The relationship between vertical and lateral PFM signals and material properties are derived analytically for two cases: transversally-isotropic piezoelectric materials in the limit of weak elastic anisotropy, and anisotropic piezoelectric materials in the limit of weak elastic and dielectric anisotropies. The integral representations for PFM response for fully anisotropic material are also obtained. The image formation mechanism for conventional (e.g., sphere and cone) and multipole tips corresponding to emerging shielded and strip-line type probes are analyzed. Resolution limits in PFM and possible applications for orientation imaging on the nanoscale and molecular resolution imaging are discussed.
Growth of Pd-Filled Carbon Nanotubes on the Tip of Scanning Probe Microscopy  [PDF]
Tomokazu Sakamoto,Chien-Chao Chiu,Kei Tanaka,Masamichi Yoshimura,Kazuyuki Ueda
Journal of Nanomaterials , 2009, DOI: 10.1155/2009/851290
Abstract: We have synthesized Pd-filled carbon nanotubes (CNTs) oriented perpendicular to Si substrates using a microwave plasma-enhanced chemical vapor deposition (MPECVD) for the application of scanning probe microscopy (SPM) tip. Prior to the CVD growth, Al thin film (10 nm) was coated on the substrate as a buffer layer followed by depositing a 5~40 nm-thick Pd film as a catalyst. The diameter and areal density of CNTs grown depend largely on the initial Pd thickness. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images clearly show that Pd is successfully encapsulated into the CNTs, probably leading to higher conductivity. Using optimum growth conditions, Pd-filled CNTs are successfully grown on the apex of the conventional SPM cantilever.
Manipulations of individual molecules by scanning probe microscopy  [PDF]
O. Dudko,A. E. Filippov,J. Klafter,M. Urbakh
Physics , 2003, DOI: 10.1021/nl034215t
Abstract: In this Letter we suggest a new method of manipulating individual molecules with scanning probes using a "pick-up-and put-down" mode. We demonstrate that the number of molecules picked up by the tip and deposited in a different location can be controlled by adjusting the pulling velocity of the tip and the distance of closest approach of the tip to the surface.
Interaction of an Asymmetric Scanning Near Field Optical Microscopy Probe with Fluorescent Molecules
Valeria Lotito;Urs Sennhauser;Christian V. Hafner;Gian-Luca Bona
PIER , 2011, DOI: 10.2528/PIER11091703
Abstract: We present a numerical analysis of the interaction between novel scanning near field optical microscopy probes based on an asymmetric structure and a single fluorescent molecule. Our finite element analysis shows how such near field probes can be effectively used for high resolution detection of single molecules, in particular those with a longitudinal dipole moment. At the same time, fluorescent molecules can be exploited as point-like probes of the single vectorial components of the near field distribution at the probe apex, providing a powerful tool for near field probe characterization.
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