Theory of the Eigler-swith

We suggest a simple model to describe the reversible field-induced transfer of a single Xe-atom in a scanning tunneling microscope, --- the Eigler-switch. The inelasticly tunneling electrons give rise to fluctuating forces on and damping of the Xe-atom resulting in an effective current dependent temperature. The rate of transfer is controlled by the well-known Arrhenius law with this effective temperature. The directionality of atom transfer is discussed, and the importance of use of non-equlibrium-formalism for the electronic environment is emphasized. The theory constitutes a formal derivation and generalization of the so-called Desorption Induced by Multiple Electron Transitions (DIMET) point of view.Comment: 13 pages (including 2 figures in separate LaTeX-files with ps-\specials), REVTEX 3.

Graphene Oxide: Fundamentals and Applications

© 2017 John Wiley & Sons, Ltd. All rights reserved.Due to its unique properties, graphene oxide has become one of the most studied materials of the last decade and a great variety of applications have been reported in areas such as sensors, catalysis and biomedical applications. This comprehensive volume systematically describes the fundamental aspects and applications of graphene oxide. The book is designed as an introduction to the topic, so each chapter begins with a discussion on fundamental concepts, then proceeds to review and summarize recent advances in the field. Divided into two parts, the first part covers fundamental aspects of graphene oxide and includes chapters on formation and chemical structure, characterization methods, reduction methods, rheology and optical properties of graphene oxide solutions. Part Two covers numerous graphene oxide applications including field effect transistors, transparent conductive films, sensors, energy harvesting and storage, membranes, composite materials, catalysis and biomedical applications. In each case the differences and advantages of graphene oxide over its non-oxidised counterpart are discussed. The book concludes with a chapter on the challenges of industrial-scale graphene oxide production. Graphene Oxide: Fundamentals and Applications is a valuable reference for academic researchers, and industry scientists interested in graphene oxide, graphene and other carbon materials

Functionalization and Reduction of Graphene Oxide

© 2017 John Wiley & Sons, Ltd.The chemistry of graphene oxide (GO) is a growing field of research. The modification of the surface properties of GO is the main goal in application-driven research. Successful functionalization protocols must be interpreted in accordance with the chemical structure of the original GO, and therefore, in this chapter, crucial aspects of the chemical structure of GO are introduced first. Next, the thermal and chemical stability of GO is reviewed, followed by introducing wet-chemical non-covalent and covalent reaction principles. The covalent functionalization of GO requires special attention. When chemical reaction principles, well known from organic chemistry, are applied to GO, it remains challenging to prove the successful accomplishment of reactions by analyzing the as-modified GO product. We pay special attention to the reactivity of the edges of defects and provide alternative explanations for interpreting experimental results, where necessary. Next, chemical reduction methods are summarized; special accent is placed on differentiating true chemical reduction from so-called "thermal reduction". Several examples for the functionalization of reduced graphene oxide (RGO) are considered next. While discussing GO chemical properties, in parallel with typical GO, we discuss these properties for the oxo-functionalized graphene (oxo-G1), a type of GO with very low density of structural defects. This sheds additional light on the role of defects in GO chemistry. Finally, additional properties of oxo-G1 are introduced. Oxo-G1 can act as a compound that enables the controlled chemistry for the design and synthesis of functional materials and devices

Surface Screening Charge and Effective Charge

The charge on an atom at a metallic surface in an electric field is defined as the field-derivative of the force on the atom, and this is consistent with definitions of effective charge and screening charge. This charge can be found from the shift in the potential outside the surface when the atoms are moved. This is used to study forces and screening on surface atoms of Ag(001) c$(2\times 2)$ -- Xe as a function of external field. It is found that at low positive (outward) fields, the Xe with a negative effective charge of -0.093 $|{e}|$ is pushed into the surface. At a field of 2.3 V \AA$^{-1}$ the charge changes sign, and for fields greater than 4.1 V \AA$^{-1}$ the Xe experiences an outward force. Field desorption and the Eigler switch are discussed in terms of these results.Comment: 4 pages, 1 figure, RevTex (accepted by PRL

Quantum Breaking of Elastic String

Breaking of an atomic chain under stress is a collective many-particle tunneling phenomenon. We study classical dynamics in imaginary time by using conformal mapping technique, and derive an analytic formula for the probability of breaking. The result covers a broad temperature interval and interpolates between two regimes: tunneling and thermal activation. Also, we consider the breaking induced by an ultrasonic wave propagating in the chain, and propose to observe it in an STM experiment.Comment: 8 pages, RevTeX 3.0, Landau Institute preprint 261/643

Atomic Scale Memory at a Silicon Surface

The limits of pushing storage density to the atomic scale are explored with a memory that stores a bit by the presence or absence of one silicon atom. These atoms are positioned at lattice sites along self-assembled tracks with a pitch of 5 atom rows. The writing process involves removal of Si atoms with the tip of a scanning tunneling microscope. The memory can be reformatted by controlled deposition of silicon. The constraints on speed and reliability are compared with data storage in magnetic hard disks and DNA.Comment: 13 pages, 5 figures, accepted by Nanotechnolog

Atomic Tunneling from a STM/AFM tip: Dissipative Quantum Effects from Phonons

We study the effects of phonons on the tunneling of an atom between two surfaces. In contrast to an atom tunneling in the bulk, the phonons couple very strongly, and qualitatively change the tunneling behavior. This is the first example of {\it ohmic} coupling from phonons for a two-state system. We propose an experiment in which an atom tunnels from the tip of an STM, and show how its behavior would be similar to the Macroscopic Quantum Coherence behavior predicted for SQUIDS. The ability to tune and calculate many parameters would lead to detailed tests of the standard theories. (For a general intro to this work on the on the World-Wide-Web: http://www.lassp.cornell.edu. Click on ``Entertaining Science Done Here'' and ``Quantum Tunneling of Atoms'')Comment: 12 pages, ReVTex3.0, two figures (postscript). This is a (substantially) revised version of cond-mat/9406043. More info (+ postscript text) at : http://www.lassp.cornell.edu/ardlouis/publications.htm

Interaction between Kondo impurities in a quantum corral

We calculate the spectral densities for two impurities inside an elliptical quantum corral using exact diagonalization in the relevant Hilbert subspace and embedding into the rest of the system. For one impurity, the space and energy dependence of the change in differential conductance $\Delta = dI/dV$ observed in the quantum mirage experiment is reproduced. In presence of another impurity, $\Delta = dI/dV$ is very sensitive to the hybridization between impurity and bulk. The impurities are correlated ferromagnetically between them. A hopping $\gtrsim 0.15$ eV between impurities destroy the Kondo resonance.Comment: 4 pages, 4 figure