Download or read book Low temperature Scanning Tunneling Microscopy Studies of Organic Molecules on Noble Metal Surfaces written by Matthias Böhringer and published by . This book was released on 1997 with total page 147 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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.
Download or read book Reactions of Organic Molecules on Metal Surfaces Studied by STM written by Markus Wahl and published by Cuvillier Verlag. This book was released on 2007 with total page 23 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Electronic Interactions at Noble Metal Surfaces Studied by Scanning Tunneling Microscopy written by Nikolaus Knorr and published by . This book was released on 2002 with total page 83 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Observations and Calculations of Adsorbed Organic Molecules and Surface Reactions on Metal Surfaces Using Scanning Tunneling Microscopy written by Don Norimi Futaba and published by . This book was released on 2000 with total page 356 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Room temperature Scanning Tunneling Microscopy Studies of Organic Molecules on Copper Surfaces written by Catherine A. Skibo and published by . This book was released on 2007 with total page 280 pages. Available in PDF, EPUB and Kindle. Book excerpt: Room temperature scanning tunneling microscopy has been used to study the behavior and properties of organic molecules on copper single crystals in an ultra high vacuum environment. The background and theory of scanning tunneling microscopy are briefly described. All the data and images presented in this dissertation were measured with a home built scanning tunneling microscope, the methods and procedures of which are outlined. The bare copper surfaces of Cu(111) and Cu(100) are imaged in order to better understand the substrate on which molecules are deposited. Various features of the single crystal surfaces are shown in images, including monatomic steps, frizzy steps, and screw dislocations. The adsorption behavior of C60 and hexa- t-butylhexaphenylbenzene (HB-HBC) have been studied on the Cu(111) surface and the adsorption behavior of hexa-t-butyldecacylene (HBDC) has been studied on the Cu(100) surface. C60 has been seen growing epitaxially from copper step edges, in a 4x4 overlayer of the Cu(111) surface. Internal structure of C60 has been observed as well. Ordered islands of HB-HBC have been observed to grow on terraces, as opposed to step edges. Brighter features in the ordered islands suggest the possible formation of dimers of HB-HBC, which is known to form dimers in the solid state. HBDC has been studied on the Cu(100) surface. At low coverage, HBDC behaves as a two-dimensional molecular gas on the surface at room temperature, with molecules resolved only along step edges and near surface defects. At monolayer coverage, HBDC forms ordered arrays, with a high level of intermolecular interactions. At lower coverage, HBDC has been pinned out of the gas phase by several different high voltage tunneling methods. At biases greater than 2 V, molecules are pinned into a semi-stable immobile trapped state by vertical manipulation, lateral manipulation and high voltage image. We believe the pinning occurs primarily through an inelastic tunneling mechanism, though the electric field and mechanical contact of the tip could contribute to the pinning.
Download or read book Low Temperature Scanning Tunneling Microscopy Studies of Surfaces and Molecules written by Lisa Marie Wesoloski and published by . This book was released on 2006 with total page 368 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanotechnology is described as an emerging science discipline that is expected to have a greater impact on life as we know it than any innovation since the industrial revolution. Superior, cheaper, stronger and more efficient products are predicted to change the way we live, use technology and conduct research. This dissertation focuses on a remarkable instrument, the low temperature scanning tunneling microscope (LT-STM), which is a powerful tool that has played a significant role in revolutionizing the fields of nanoscience and nanotechnology. The work in this dissertation is divided into three sections. First, the fundamental principles of nanoscience and the history of microscopy are introduced. The second part provides a thorough study of Bardeen's formula and its application in STM. The third part describes experimental investigations involving the physicochemical properties of matter at the nanoscale conducted by means of LT-STM. Studies begin with bare substrate surfaces and successively build in complexity as small molecules, solvents, nanoclusters and large organic molecules are examined on surfaces. Experiments show that carbon monoxide exhibits chemical contrast, while oxygen shows a lack thereof. Solvents are demonstrated to weaken surface bonds and induce surface atom mass transport and the tip is shown to assist the diffusion. Manganese nanoclusters are shown to generate a localized electronic state on graphite by either an electronic or magnetic perturbation. The aromatic molecule, decacyclene (DC) is shown to exhibit both bias-dependent and tip-dependent contrast reversal. In addition, intermolecular interactions are found to compete with the surface-to-molecule interactions as dimers are observed on the surface. Two geometric orientations of the dimers are proposed to explain dimer characteristics and their relation to substrate-dependent properties. Lastly, DC molecules are examined at coverages in excess of a monolayer and shown to form ordered domains of the boat-shape conformation. This dissertation emphasizes the local modifications of electronic structures upon physisorption and the interplay between surface-to-molecule and molecule-to-molecule interactions, which demonstrate the various complexities occurring at the nanoscale.
Download or read book Scanning Tunneling Microscopy Studies of Organic Monolayers Adsorbed on Th Rhodium 111 Crystal Surface written by Paul Davis Cernota and published by . This book was released on 1999 with total page 272 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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.
Download or read book Variable temperature scanning tunneling microscopy studies of atomic and molecular level surface phenomena on semiconductor and metal surfaces written by William Patrick Fitts and published by . This book was released on 2001 with total page 704 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Constructing Two dimensional Molecular Networks on Metal and Semiconducting Surfaces written by Renjie Liu and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The synthesis of two-dimensional organic nanostructures on metal and semiconducting surfaces is studied under ultra-high vacuum (UHV) conditions. Three halogenated organic molecules are investigated using scanning tunneling microscopy (STM) on both metal and semiconducting substrates. The first system studied is the adsorption of brominated tetrathienoanthracene (TBTTA) molecules onto the Si(111) √3×√3 R30°-Ag (Si(111) √3-Ag) surface at room temperature. STM images reveal that at low coverage, the molecules readily migrate to step edges and defects in the √3 overlayer. With increasing coverage, the molecules eventually form compact supramolecular structures. At higher coverage (0.4 - 0.6 monolayers), the spatial extent of the supramolecular structures is often limited by defects in the underlying √3 layer. Our results suggest that the √3-Ag surface provides a relatively inert substrate for the adsorption of TBTTA molecules, and that the supramolecular structures are held together by relatively weak intermolecular forces. The second organic molecule investigated is 2,4,6-tris(4-iodophenyl)-1,3,5-triazine (TIPT). Molecules are deposited onto two related surfaces, Ag(111) and Si(111) √3-Ag. On the Ag(111) surface, TIPT molecules dehalogenate spontaneously upon deposition and form organometallic structures at room temperature. Gentle annealing at ~ 100 °C leads to a more ordered molecular network characterized almost exclusively by hexagons and polymerization was confirmed after further annealing at ~135 °C. On the Si(111) √3-Ag surface TIPT molecules remain largely intact and readily diffuse to step edges and defects in the √3 overlayer. At low coverage, most images display regularly spaced "fuzzy lines" which indicate molecular diffusion at room temperature. At higher coverage (0.4 - 0.8 monolayers), supramolecular domains are formed. The geometry of the cell is similar to an energy optimized 2-d free-standing TIPT layer determined by DFT indicating that de-halogenation does not occur on the Si(111) √3-Ag surface at room temperature and that the supramolecular domains are characterized by zig-zag rows of intact monomers held together primarily by I···H hydrogen-like bonding. Finally, the adsorption of 2,6,10-tribromo-4,8,12-trioxa-3a2-azadibenzo[cd,mn]pyrene (TBTANG) molecules is detailed on both Au(111) and Si(111) √3-Ag surfaces. Dosing TBTANG molecules onto a Au(111) surface at room temperature leads to the self-assembly of intact molecules while deposition onto a hot Au(111) surface yields a complete polymer layer. On the Si(111) √3-Ag surface the molecules display high mobility. With increasing coverage, TBTANG exhibits long-range self-assembly of intact molecules. As the coverage approaches one monolayer, the self-assembled layer extends over the entire surface. Defects in the √3-Ag substrate affect the integrity of domains, but do not limit the size. Preliminary annealing experiments do not lead to polymerization of the TBTANG layer. Rather, annealing at ~ 90°C leads to disordered regions which nucleate primarily at step edges.
Download or read book Japanese Journal of Applied Physics written by and published by . This book was released on 2005 with total page 1772 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 692 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Scanning Tunneling Microscopy and Spectroscopy of Metal Organic Complexes written by Kezilebieke Shawulienu and published by . This book was released on 2014 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the bottom up approach of today's nanoscience, the supramolecular assembly of metal atoms and molecules on surfaces is leading to functional compounds, relevant to many applications in optoelectronics, magnetism, and catalysis. It has been found that in some cases high magnetic spin states and strong magnetic anisotropy appear as a result of electron transfer between ligands, surface and metal atom. The focus of this thesis lies on the self assembling of 1,2,4,5-Tetracyanobenzene (TCNB) and Fe-TCNB coordination nanostructures on the Au(111) surface. The structural formation is directed by the non covalent interactions. Scanning tunneling spectroscopy (STS) reveal that the TCNB molecules are physisorbed on Au(111) surface. By detail analysis of the dI/dV spectra above the TCNB monolayer on the Au(111) surface, we found that the TCNB molecules on Au(111) shows a negligible charge transfer with Au(111) substrate and a small adsorption energy of 0.5 eV per TCNB molecules. STS measurement provide a HOMO-LUMO gap of 3 eV in agreement with DFT calculations. By controlling the fabrication parameters, surface coordination nanostructures with different chemical composition or molecular packing have been synthesized. The electronic properties have been characterized by the local dI/dV analysis of the metal centers at different steps of a Fe-(TCNB)x (x=4, 2) complexes formation. At low temperature deposition, first form an ordered metastable intermediate. STM data yield the bond angle between the Fe-N-C is 120°. The scanning tunneling spectroscopy reveal that Fe atoms and the TCNB molecules keep their identity while the Fe atoms localize the surface-state electrons similar to what they do on the bare Au(111) surface. This result indicates that the TCNB molecules are virtually in the same electronic state as before the Fe adsorption. The situations are different when the deposition performance at room temperature. When the temperature is changed, to room temperature, the original entities transform into the Fe(TCNB)4 monomer complexes with 180° Fe-N-C bond angles. The STS above the Fe(TCNB)4 complex strongly suggest that the coordination bond had been formed between the Fe atom and the TCNB ligands. DFT calculations support the conclusions and drawn from experimental studies and assist the interpretations of experiment. Further structural complexation is achieved by the synthesis of Fe(TCNB)2 network. The network has a square structure with a regular separation of the magnetic Fe atoms in the network. The electronic information is gathered from the spectroscopic labeling of FePc to identify some of the resonances of the Fe(TCNB)2 network. There are similar features are found in the dI/dV spectra above the Fe atoms and ligand in both system, indicating that the Fe somehow feels a similar environment from the TCNB ligands in the network and in the FePc molecules. Further analysis of this feature have been disused by means of metal-ligand bond formation.
Download or read book Self assembly Dynamics and Reactions of Organic Molecules on Metal Surfaces written by Sigrid Weigelt and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Structures and Dynamics of Atomic and Molecular Adsorbates on Metal Surfaces by Scanning Tunneling Microscopy and Low Energy Electron Diffraction written by Hyungsuk Alexander Yoon and published by . This book was released on 1996 with total page 394 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Scanning Tunneling Microscopy and Spectroscopy of Functional Molecules on Metal Surfaces written by Xin Ge and published by . This book was released on 2006 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
