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Scanning Tunneling Microscopy Studies Of Metal Clusters Supported On Graphene And Silica Thin Film
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Book Synopsis Scanning Tunneling Microscopy Studies of Metal Clusters Supported on Graphene and Silica Thin Film by : Zihao Zhou
Download or read book Scanning Tunneling Microscopy Studies of Metal Clusters Supported on Graphene and Silica Thin Film written by Zihao Zhou and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The understanding of nucleation and growth of metals on a planar support at the atomic level is critical for both surface science research and heterogeneous catalysis studies. In this dissertation, two planar substrates, including graphene and ultra-thin silica film were employed for supported model catalysts studies. The structure and stability of several catalytically important metals supported on these two substrates were thoroughly investigated using scanning tunneling microscopy (STM) coupled with other traditional surface science techniques. In the study of the graphene/Ru(0001) system, the key factors that govern the growth and distribution of metals on the graphene have been studied based on different behaviors of five transition metals, namely Pt, Rh, Pd, Co, and Au supported on the template of a graphene moire pattern formed on Ru(0001). Both metal-carbon (M-C) bond strength and metal cohesive energies play significant roles in the cluster formation process and the M-C bond strength is the most important factor that affects the morphology of clusters at the initial stages of growth. Interestingly, Au exhibits two-dimensional (2-D) structures that span several moire unit cells. Preliminary data obtained by dosing molecular oxygen onto CO pre-covered Au islands suggest that the 2-D Au islands catalyze the oxidation of CO. Moreover, graphene/Ru(0001) system was modified by introducing transition metals, oxygen or carbon at the interface between the graphene and Ru(0001). Our STM results reveal that the geometric and/or electronic structure of graphene can be adjusted correspondingly. In the study of the silica thin film system, the structure of silica was carefully investigated and our STM images favor for the [SiO4] cluster model rather than the network structure. The nucleation and adsorption of three metals, namely Rh, Pt and Pd show that the bond strength between the metal atom and Si is the key factor that determines the nucleation sites at the initial stages of metal deposition. The annealing effect studies reveal that Rh and Pt atoms diffuse beneath the silica film and form the 2-D islands that are covered with a silica thin film. In contrast, the formation of Pd silicide was observed upon annealing to high temperatures.
Book Synopsis Controlled Synthesis and Scanning Tunneling Microscopy Study of Graphene and Graphene-Based Heterostructures by : Mengxi Liu
Download or read book Controlled Synthesis and Scanning Tunneling Microscopy Study of Graphene and Graphene-Based Heterostructures written by Mengxi Liu and published by Springer. This book was released on 2017-10-10 with total page 106 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis focuses on the energy band engineering of graphene. It presents pioneering findings on the controlled growth of graphene and graphene-based heterostructures, as well as scanning tunneling microscopy/scanning tunneling spectroscopy (STM/STS) studies on their electronic structures. The thesis primarily investigates two classes of graphene-based systems: (i) twisted bilayer graphene, which was synthesized on Rh substrates and manifests van Hove singularities near Fermi Level, and (ii) in-plane h-BN-G heterostructures, which were controllably synthesized in an ultrahigh vacuum chamber and demonstrate intriguing electronic properties on the interface. In short, the thesis offers revealing insights into the energy band engineering of graphene-based nanomaterials, which will greatly facilitate future graphene applications.
Book Synopsis Scanning Tunneling Microscopy in Surface Science, Nanoscience, and Catalysis by : Michael Bowker
Download or read book Scanning Tunneling Microscopy in Surface Science, Nanoscience, and Catalysis written by Michael Bowker and published by John Wiley & Sons. This book was released on 2009-11-11 with total page 258 pages. Available in PDF, EPUB and Kindle. Book excerpt: Here, top international authors in the field of STM and surface science present first-class contributions on this hot topic, bringing the reader up to date with the latest developments in this rapidly advancing field. The focus is on the nanoscale, particularly in relation to catalysis, involving developments in our understanding of the nature of the surfaces of oxides and nanoparticulate materials, as well as adsorption, and includes in-situ studies of catalysis on such model materials. Of high interest to practitioners of surface science, nanoscience, STM and catalysis.
Book Synopsis Variable-Temperature Scanning Tunneling Microscopy Studies of Growth and Characterization of Hexagonal Boron Nitride and Graphene Layers by : Pedro Arias
Download or read book Variable-Temperature Scanning Tunneling Microscopy Studies of Growth and Characterization of Hexagonal Boron Nitride and Graphene Layers written by Pedro Arias and published by . This book was released on 2019 with total page 125 pages. Available in PDF, EPUB and Kindle. Book excerpt: Two-dimensional (2D) materials, such as graphene and hexagonal boron nitride (hBN) have attracted attention from both academia and industry owing to their unique atomically thin structure and associated properties. The goal of this dissertation is to provide fundamental insights of the growth kinetics, surface structure, and thermal stability of hBN and graphene layers grown via chemical vapor deposition (CVD) on metal substrates. Scanning tunneling microscopy (STM) was used to investigate the surface structure of hexagonal boron nitride (hBN) domains on Pd(111) grown via dissociative chemisorption of borazine on Pd(111)/Al2O3(0001) thin films. STM images acquired from the hBN/Pd(111) sample reveal moir patterns with different periodicities corresponding to rotational domains of hBN. Surface corrugations in each of the moir patterns were measured from the STM images as a function of the STM tunneling parameters. The corrugation amplitude z was found to depend on the tunneling bias and increases with increasing . The observed tunneling-parameter dependence in z were attributed to the electronic structure of the hBN/Pd(111) system. The domains with the largest , exhibit a bifurcation behavior in which some domains are nearly flat, and others develop "blisters", i.e., significant hills-and-valley geometric undulations. Hence, unlike any other monolayer hBN-on-metal system, hBN/Pd can have either mainly geometric or mainly electronic corrugation, depending on the domain orientation. The growth kinetics of hBN monolayers grown via CVD using borazine (B3N3H6) on Pd(111) were investigated using in situ variable-temperature STM. STM images were acquired during CVD of borazine on Pd(111) as a function of the substrate temperature T, the borazine partial pressure P, and time t. The STM images reveal a T and P dependent change in the growth mode: at higher P and lower T, (lower P and higher T), hBN nucleation occurs primarily on Pd step edges (Pd terraces). Furthermore, the mechanisms promoting growth across the step edges (as a carpet across steps) are identified. These results provide new insights into the nucleation and growth of hBN monolayers and potentially other 2D materials and related heterostructures on metal substrates. The thermal stability of hBN covered Pd(111) thin films was investigated using in situ variable-temperature STM. STM images were acquired from bare Pd(111) and hBN covered Pd(111) at temperatures between 600 K and 1000 K. It was found that the hBN overlayer enhances the stability of the underlying Pd surface by suppressing the surface mobility of adatoms. These results provide new, direct insights into the behavior of substrate supported 2D materials at elevated temperatures. Finally, in situ VT-STM was used to investigate the growth of graphene using benzene (C6H6) on Pd(111). STM images were acquired during and after benzene deposition at temperatures between 300 K and 1100 K. Compared to growth of graphene on Pd(111) using other hydrocarbon precursors (e.g. ethylene), benzene enables the growth of graphene at lower T, and at significantly lower doses, likely due to an increased probability of forming C6 and/or C6Hx(x
Book Synopsis Scanning Tunneling Microscopy and Related Methods by : R.J. Behm
Download or read book Scanning Tunneling Microscopy and Related Methods written by R.J. Behm and published by Springer Science & Business Media. This book was released on 2013-03-09 with total page 516 pages. Available in PDF, EPUB and Kindle. Book excerpt: Proceedings of the NATO Advanced Study Institute on Basic Concepts and Applications of Scanning Tunneling Microscopy, Erice, Italy, April 17-29, 1989
Book Synopsis Scanning Tunneling Microscopy Studies of Fluorinated Graphene Films and Field-directed Sputter Sharpening by :
Download or read book Scanning Tunneling Microscopy Studies of Fluorinated Graphene Films and Field-directed Sputter Sharpening written by and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Scanning Tunneling Microscopic Studies of Metal Clusters Supported on TiO[subscript 2](110) by : Xiaofeng Lai
Download or read book Scanning Tunneling Microscopic Studies of Metal Clusters Supported on TiO[subscript 2](110) written by Xiaofeng Lai and published by . This book was released on 2000 with total page 388 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Scanning, Tunneling Microscopy of Metals on Graphite by : Eric David Ganz
Download or read book Scanning, Tunneling Microscopy of Metals on Graphite written by Eric David Ganz and published by . This book was released on 1989 with total page 410 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Scanning Tunneling Microscopy II by : Roland Wiesendanger
Download or read book Scanning Tunneling Microscopy II written by Roland Wiesendanger and published by Springer. This book was released on 1992 with total page 332 pages. Available in PDF, EPUB and Kindle. Book excerpt: Vol. 2.
Book Synopsis Low Temperature Scanning Tunneling Microscopy Studies of Single Molecules Adsorbed on Thin Insulating Films by :
Download or read book Low Temperature Scanning Tunneling Microscopy Studies of Single Molecules Adsorbed on Thin Insulating Films written by and published by . This book was released on 2008 with total page 120 pages. Available in PDF, EPUB and Kindle. Book excerpt: The present work is concentrated on the study of two isomers of an organic molecule -methylterrylene- adsorbed on a thin insulating _lm (a NaCl bi or tri-layer) deposited on a metallic substrate -Cu(111)-, by Scanning Tunneling Microscopy and Spectroscopy (STM and STS). Most STM studies of adsorbed atoms and molecules up to now have been performed on metallic or semiconducting surfaces. In this situation, the object is strongly electronically coupled to the substrate. The atomic or molecular levels are then shifted and broadened in energy, with the consequence that some of the intrinsic properties of the object are lost, to a more or less large extend. It has been shown recently that interposing between this object and the substrate an insulating leads to an efficient decoupling which allows to recover some of these properties. This decoupling effect of the insulating layer is at the center of the work reported here. Experiments where the molecules are directly adsorbed on the metal are compared with experiments where the molecule is decoupled from the Cu(111) surface by a NaCl bi-layer. The interpretation of these experimental results is supported and extended by current and image calculations with the Elastic Scattering Quantum Chemistry method where the structure of the Metal-insulating layer-molecule-metal junction is described at the atomic level. In the framework of molecular electronics, where the objective is to design and use molecules as electronic devices, understanding and controlling the coupling of a molecule to its environment is a central issue.
Book Synopsis Scanning Tunneling Microscopy and Low Energy Electron Microscopy of Metal Overlayers on Metal Surfaces by :
Download or read book Scanning Tunneling Microscopy and Low Energy Electron Microscopy of Metal Overlayers on Metal Surfaces written by and published by . This book was released on 1995 with total page 47 pages. Available in PDF, EPUB and Kindle. Book excerpt: Thin metal films are of ever increasing importance as the scale of devices shrinks. In order to provide new insight into the atomic details of metal film structure and the nanoscopic details of magnetic domains, efforts were made to study thin metal films on tungsten single crystals using both scanning tunneling microscopy (STM) and spin polarized low energy electron microscopy (SPLEEM). Difficulties were encountered with the as-delivered SPLEEM instrument which required extensive efforts to rectify. STM investigators were directed towards understanding the structure of multilayer metal films on W(111) and Al2O3(0001). Atomic models for a number of different and complex surface structures are derived for Au films on W(l10) for coverages between 0.5 and 5 monolayers. STM studies of sputter deposited Pt films on sapphire substrates, for use as seed layers for epitaxial spin valves, are described. By varying the Pt layer thickness and deposition temperature, continuous epitaxial thin films were developed. An epitaxial spin valve was constructed and assessed by magneto-transport measurements. Future opportunities for improved understanding of magnetic and electrical phenomena in thin films are briefly described. p1.
Book Synopsis Scanning Tunneling Microscopy Studies of Growth and Adsorption on Transition Metal Surfaces by : Morten Østergaard Pedersen
Download or read book Scanning Tunneling Microscopy Studies of Growth and Adsorption on Transition Metal Surfaces written by Morten Østergaard Pedersen and published by . This book was released on 1998 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Scanning Tunneling Microscopy Studies of Clusters and Materials Modification at the Nanometer Scale by : Gordon Michael Shedd
Download or read book Scanning Tunneling Microscopy Studies of Clusters and Materials Modification at the Nanometer Scale written by Gordon Michael Shedd and published by . This book was released on 1991 with total page 350 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Real-time Scanning Tunneling Microscopy Studies of Thin Film Deposition and Ion Erosion by : Vincent Fokkema
Download or read book Real-time Scanning Tunneling Microscopy Studies of Thin Film Deposition and Ion Erosion written by Vincent Fokkema and published by . This book was released on 2011 with total page 151 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Low Temperature Scanning Tunneling Microscope Study of Metallic Thin Films and Nanostructures on the Semiconductor Substrates by : Shengyong Qin
Download or read book Low Temperature Scanning Tunneling Microscope Study of Metallic Thin Films and Nanostructures on the Semiconductor Substrates written by Shengyong Qin and published by . This book was released on 2008 with total page 254 pages. Available in PDF, EPUB and Kindle. Book excerpt: Many properties of the thin films are different from the bulk value and in many cases, depend dramatically on the film thickness. In the metallic ultra-thin films epitaxially grown on the semiconductor substrate, the conduction electrons are confined by the vacuum and metal-semiconductor interface. When the film thickness is comparable to the electron Fermi wavelength, this confinement will produce discrete energy levels known as quantum well states (QWS), which dramatically modify the electronic structures of the thin film and this is called quantum size effect (QSE). QSE will have a profound effect on a lot of physical properties of the thin films. Among various systems exhibiting QSE, Pb/Si (111) is the most widely studied one and exhibits the richest phenomena in QSE. In this study, a home made low temperature Scanning Tunneling Microscopy/Spectroscopy (LT-STM/S) was used to study the superconductivities of the Pb thin films. Quantum oscillations of the superconductivity have been observed for the films down to 4 monolayer and the oscillation amplitude increases as the film gets thinner. To resolve the discrepancies between the superconductivities measured with ex-situ transport and in-situ STS. We also studied the influence of Au overlay on the Pb thin films with LT-STM/S, and found out the deposition of Au on Pb dramatically roughened the Pb films. Finally, we successfully grew large scale near perfect 2ML Pb films. There are two types of films which exhibit different Moiré patterns. LT-STS studies revealed there is big difference in the superconductivity Tc of these two films, both of which decreased dramatically from that of the 4ML film.
Book Synopsis Development of a Scanning Probe Microscope and Studies of Graphene Grown on Copper by : Haider Imad Rasool
Download or read book Development of a Scanning Probe Microscope and Studies of Graphene Grown on Copper written by Haider Imad Rasool and published by . This book was released on 2012 with total page 117 pages. Available in PDF, EPUB and Kindle. Book excerpt: A description of the construction of a low noise fiber interferometer deflection sensor is presented in order to illustrate the capabilities of the developed home built scanning probe microscope (SPM). A description of the critical components and a rationale behind their implementation in the design of the sensor is provided. An analysis of an ideal interference cavity is used to understand the optimization of the deflection sensor towards achieving the highest possible sensitivity and lowest deflection noise density. The low noise interferometer can be used to detect the motion of micron sized resonators without the need for external lenses or polarization sensitive optical components, allowing for simplified implementation in a variety of circumstances. True atomic resolution imaging of muscovite mica in water by atomic force microscopy (AFM) is demonstrated using the developed sensor in the home built SPM. Results on graphene grown on copper substrates by chemical vapor deposition (CVD) is provided. Graphene appears to grow over grains of different identities and across grain boundaries of the copper. Graphene island growth on the surface appears to depend on the underlying substrate. Temperature dependent growth studies show a significant decrease in growth rate with decreasing temperature. The graphene grown on copper is shown to be transferable to arbitrary substrates and can be suspended across perforations in a receiving substrate. The knowledge gained from the growths on copper allowed for the successful fabrication of a new type of hybrid polymeric - conductive AFM probe using patterned silicon substrates and thin copper films. Scanning tunneling microscopy (STM) was performed on graphene grown on copper substrates using the home built instrument. First, atomic scale STM imaging of graphene on polycrystalline copper substrates was accomplished. Graphene is shown to grow continuously over atomic steps, edges, and vertices of these corrugated copper surfaces. Continuous graphene growth is observed to exist over facets of different identities. The results on polycrystalline copper strongly suggests that the copper atoms are mobile during growth and that the underlying substrate does not limit graphene growth. In addition, STM was performed on graphene grown on copper (100) single crystals. The growth is again shown to be continuous over a wide range of surface features. The grown graphene exists in a variety of orientations with respect to the underlying copper crystal lattice. This leads to graphene overlayers which are polycrystalline in nature. Transmission electron microscopy (TEM) is used to reveal the crystallinity of graphene grown on single crystals and the real space distribution of the crystal domains in grown graphene. The compiled results of graphene growth on copper suggest that understanding and controlling the nucleation at the surface will ultimately be required for wafer scale growth of monolayer single crystal graphene on copper.
Book Synopsis Scanning Tunneling Microscopy and Spectroscopy Studies of Graphene by : Adina Luican-Mayer
Download or read book Scanning Tunneling Microscopy and Spectroscopy Studies of Graphene written by Adina Luican-Mayer and published by . This book was released on 2012 with total page 143 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the two-dimensional (2D) lattice of graphene, consisting of carbon atoms arranged in a honeycomb lattice, the charge carriers are described by a Dirac-Weyl Hamiltonian. Seeking to understand their unique nature, this thesis presents results of scanning tunneling microscopy (STM) and spectroscopy (STS) experiments at low temperatures and in magnetic fi eld. These techniques give access, down to atomic scales, to structural information as well as to the electronic properties of graphene. The main findings include the observation of quantized Landau levels (LL) in the presence of magnetic field, their dependence on carrier density and e ffects of charged impurities and other disorder on the LL spectrum. Twisting graphene layers away from the equilibrium Bernal stacking leads to the formation of Moir e patterns that signi ficantly alter the electronic properties of graphene stacks. The second part of the thesis discusses the eff ects of such rotations on the electronic properties as a function of twist angle.
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