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Low Temperature Scanning Tunneling Microscopy Studies Of The Surface And Impurity States In Narrow Gap Semiconductors
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Book Synopsis Low Temperature Scanning Tunneling Microscopy Studies of the Surface and Impurity States in Narrow Gap Semiconductors by : Sergei Urazhdin
Download or read book Low Temperature Scanning Tunneling Microscopy Studies of the Surface and Impurity States in Narrow Gap Semiconductors written by Sergei Urazhdin and published by . This book was released on 2002 with total page 246 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Low Temperature Scanning Tunneling Microscopy Studies of Surfaces and Molecules by : Lisa Marie Wesoloski
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.
Book Synopsis Scientific and Technical Aerospace Reports by :
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 704 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Dissertation Abstracts International by :
Download or read book Dissertation Abstracts International written by and published by . This book was released on 2009 with total page 810 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 American Doctoral Dissertations by :
Download or read book American Doctoral Dissertations written by and published by . This book was released on 2001 with total page 776 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Scanning Tunneling Microscopy and Spectroscopy of Aluminum Based Quasicrystals and Approximants by : Ruben Rafael Mäder
Download or read book Scanning Tunneling Microscopy and Spectroscopy of Aluminum Based Quasicrystals and Approximants written by Ruben Rafael Mäder and published by Logos Verlag Berlin GmbH. This book was released on 2010 with total page 167 pages. Available in PDF, EPUB and Kindle. Book excerpt: On the nanometer scale, the local variation of the electronic density of states of aluminum based complex metallic alloys (quasicrystals and approximants) is experimentally investigated by low temperature scanning tunneling spectroscopy. We report on the correlation between the local variations of the electronic density of states and the electrical resistivity. The surface structure is investigated by scanning tunneling microscopy, low energy electron diffraction, and X-ray photoemission diffraction. Experimental results are interpreted on the basis of the respective bulk structure models.
Book Synopsis Scanning Tunneling Microscopy Studies of Small Aromatic Molecules on Semiconductor Surfaces by : Alfred John Weymouth
Download or read book Scanning Tunneling Microscopy Studies of Small Aromatic Molecules on Semiconductor Surfaces written by Alfred John Weymouth and published by . This book was released on 2009 with total page 190 pages. Available in PDF, EPUB and Kindle. Book excerpt: Understanding the behaviour of molecules on a semiconductor surface is necessary if molecular self-assembly is going to be employed, with existing semiconductor technology, to create useful devices. Si(111)-7x7 is an invaluable surface upon which to study molecular adsorption. The surface reconstruction has been well characterized and it possesses seven symmetrically distinct dangling bonds that can serve as reaction sites. Aromatic molecules on Si(111)-7x7 have been investigated with a variety of techniques and have been shown to chemisorb at room temperature. However, it is not trivial to predict how an ensemble of aromatic molecules might distribute themselves amongst the available bonding sites on this surface. The work presented in this thesis begins with a joint STM and ab initio investigation of thiophene on 7x7 that demonstrates kinetics are necessary to describe the chemisorption sites occupied at various coverages. A kinetic Monte Carlo model, taking into account a mobile physisorbed state, is shown to accurately describe this site occupancy at room temperature. This model disregards molecule-molecule interaction because thiophene does not sterically hinder chemisorption to a neighbouring dangling bond. A larger molecule, mesitylene, was then studied on Si(111)-7x7, and shown to form an ordered molecular lattice on the Si(111)-7x7 surface. This is the first demonstration of a porous molecular lattice grown on Si(111)-7x7 at room temperature. Finally, molecular chemisorption on the related 5x5 reconstruction, grown by depositing Ge on 7x7, is studied. It is found that the presence of Ge hinders molecular chemisorption, preventing formation of the mesitylene lattice.
Book Synopsis Scanning Tunneling Microscopy of Two-dimensional Materials by : Grady A. Gambrel
Download or read book Scanning Tunneling Microscopy of Two-dimensional Materials written by Grady A. Gambrel and published by . This book was released on 2017 with total page 131 pages. Available in PDF, EPUB and Kindle. Book excerpt: Two-dimensional materials are of fundamental and practical interest due to the unique properties they exhibit. As they are only one layer or one atom thick, their physical and electronic properties are sensitive to their local environment, and may be manipulated by engineering variations within the materials. Incorporating these materials into electronic devices requires that their interactions are well understood so that they behave as predicted. For this reason, the study of defects, likely contaminants, and engineered structures is worthwhile. The scanning tunneling microscope is of particular use in such experiments as it can be used to characterize the atomic structure and locally measure the electronic properties of samples. Graphene islands were grown on Cu(111) in ultrahigh vacuum to study graphene/copper interactions with minimal surface adsorbates. Using in situ low-temperature scanning tunneling microscopy (STM), both the physical and electronic structure were measured with atomic spatial resolution and compared with those of clean copper regions. These measurements indicate a decrease in the work function relative to clean Cu(111) and reduced coupling of surface electronic states to the bulk. Other measurements find that both the band edge and effective mass of Shockley surface state electrons are infuenced by the graphene layer. Similarly, single-layer germanene was grown on and measured on Cu(111). A competing alloy process which forms Cu2Ge restricts notable germanene coverage to a substrate temperature range between 40 degrees and 150 degrees Celsius. Atomic resolution imaging and tunneling spectroscopy are used to distinguish germanene and Cu2Ge regions, and probe the interaction of both with the Cu(111) substrate. Germanene was found to be weakly coupled to the Cu(111), maintaining an incommensurate 3.8 Angstrom lattice but lack any clear signatures of the Dirac point. In contrast, a 4.4 Angstrom lattice is observed on Cu2Ge that is commensurate with a v3 x v3 R30 reconstruction of Cu(111), and distinct unoccupied electronic states are observed well above the sample Fermi level.
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 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 Low Temperature Scanning Tunneling Microscope Study of Metallic Thin Films on the Semiconductor Substrates by : Daejin Eom
Download or read book Low Temperature Scanning Tunneling Microscope Study of Metallic Thin Films on the Semiconductor Substrates written by Daejin Eom and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Scanning Tunneling Microscopy and Spectroscopy by : Dawn Bonnell
Download or read book Scanning Tunneling Microscopy and Spectroscopy written by Dawn Bonnell and published by Wiley. This book was released on 1993-03-29 with total page 436 pages. Available in PDF, EPUB and Kindle. Book excerpt: Scanning tunneling microscopy (STM) provides three-dimensional real- space images of surfaces at high spatial resolution. When the surface is flat and clean, even atoms can be imaged. Its extreme usefulness has led it to near instantaneous acceptance as a characterization tool. This book covers fundamental concepts of STM operation, image interpretation, instrumentation, and techniques for various applications. It als contains advanced treatments of theory and spectroscopy. Surface physicists, electrochemists, materials scientists, and other scientists who see a use for STM will find the depth of coverage and accompanying reference lists in this book essential to their work. In addition, those who wish to add the capabilities of probe microscopy to their operations, such as microscopists and quality control engineers, will find the basic information in this book.
Book Synopsis Variable-temperature scanning tunneling microscopy studies of atomic and molecular level surface phenomena on semiconductor and metal surfaces by : William Patrick Fitts
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:
Book Synopsis Low-temperature Scanning Tunneling Microscopy Studies of Organic Molecules on Noble Metal Surfaces by : Matthias Böhringer
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:
Book Synopsis Restoration of a Low Temperature Scanning Tunneling Microscope by : Baird Bankovic
Download or read book Restoration of a Low Temperature Scanning Tunneling Microscope written by Baird Bankovic and published by . This book was released on 2024 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Scanning tunneling microscopy is a technique that enables the study of the surfaces of materials with sub-nanometer resolution. A scanning tunneling microscope (STM) gives local electronic information about the surface and is an invaluable analysis technique in modern condensed matter physics. The goal of my project was to restore an existing low temperature STM which had fallen into disrepair. This thesis outlines the restoration process, along with a description of the supporting techniques that were necessary. In parallel with the restoration process, I also developed an automated tungsten tip fabricator for making atomically sharp tips for the STM. This is an original design that I have shared on an open source website. Additionally, I explored the use of a low temperature transimpedance preamplifier that would improve the performance of our STM and tested a number of operational amplifiers that could be used to this end.
Book Synopsis In Situ Studies of the Determination of Surface States at the Semiconductor/solution Interface by : Anuncia Gonzalez-Martin
Download or read book In Situ Studies of the Determination of Surface States at the Semiconductor/solution Interface written by Anuncia Gonzalez-Martin and published by . This book was released on 1993 with total page 664 pages. Available in PDF, EPUB and Kindle. Book excerpt:
