Unravelling the electrical properties of epitaxial Graphene nanoribbons

The size-dependent electrical resistivity of single-layer graphene ribbons has been studied experimentally for ribbon widths from 16 nm to 320 nm. The experimental findings are that the resistivity follows a more dramatic trend than that seen for metallic nanowires of similar dimensions, due to a combination of surface scattering from the edges, band-gap related effects and shifts in the Fermi level that show a strong width dependence. We show that the Charge Neutrality point switches polarity below a ribbon width of around 50 nm, and that at this point, the thermal coefficient of resistance is a maximum. The majority doping type therefore can be controlled by altering ribbon width. We also demonstrate that an alumina passivation layer has a significant effect on the mean free path of the charge carriers within the graphene, which can be probed directly via measurements of the width-dependent resistivity. We propose a model for conduction that takes edge and confinement effects into account

An Econometric Model of Non-Agricultural Stock Changes. Quarterly Economic Commentary Special Article, December 1977

Macroeconometric models pay particular attention to the equations dealing with the major components of aggregate demand, such as consumption, investment and exports. In the Central Bank's econometric model [l], investment is broken down into three components: residential investment, non-residential investment and stockbuilding. While stockbuilding is a relatively small proportion of aggregate demand, it is a volatile magnitude and has traditionally been accorded an important place in the study of economic fluctuations. This note is devoted to a discussion of the stockbuilding equation. The following sections deal with the models tested, the empirical results and the conclusions. Data, sources and methods are given in the appendix

Economic Aspects of the Irish Exchange Control Regime. Quarterly Economic Commentary Special Article, April 1980

From the foundation of the State until March 1979, the Irish currency was maintained in a fixed one-to-one parity with the pound sterling. Aside from the 50% deposit requirement on capital inflows through the banking system imposed by the Central Bank in recent years, there were no significant restrictions on the movement of funds between Ireland and the sterling area. Capital movements between Ireland and non-sterling countries were subject to exchange control regulations broadly similar to the UK's own, although in practice they were administered in a somewhat more liberal fashion. The Irish controls could be seen as, in effect, part of the price of our membership of the sterling zone, since the UK's own controls would have been circumvented very readily if Ireland had presented an uncontrolled "window" to the rest of the world. So purchases of financial assets in non-sterling countries had to be financed through the dollar premium pool or through foreign currency loans

Electron transport behavior of quinoidal heteroacene-based junctions: effective electron-transport pathways and quantum interference.

The electron transport behavior through a series of molecular junctions composed of tetracene (TC) and S/O substituted-TC (S/O-TC) has been studied using density functional theory (DFT) combined with the non-equilibrium Green's function (NEGF) method. The unique transport behavior has been interpreted using correlated quantum interference and electron transport pathway models. In the TC system, two dominant electron transfer channels exist as demonstrated by a detailed transmission pathway analysis. In the substituted S/O-TC systems, the electron transport behavior is regulated through either constructive or destructive quantum interference due to the existence of additional p-electrons, leading to a significant diversity of current-voltage curves. Compared to the TC molecule in the bias region from 0 to 1.0 V, an α-connected molecular junction exhibits a greater current, whereas a β-connected molecular junction shows a smaller current. The substitution with O and S atoms shows a minor effect on the conductance of the molecular junctions. In order to clarify the role of heteroatoms, a series of artificial models designed by removing specific sulfur and carbon atoms in α-S-TC have been investigated in detail. The results have demonstrated that only the S heteroatom on one side of the molecule contributes to the junction conductivity through constructive quantum interference. It has also been observed that current exchange occurs between the two electron transfer channels

Adsorption of 4-n-Nonylphenol, Carvacrol, and Ethanol onto Iron Oxide from Nonaqueous Hydrocarbon Solvents.

The adsorption of 4-n-nonylphenol (4NP), carvacrol, and ethanol onto the surface of iron oxide from nonaqueous solutions is presented. It is found that adsorption of 4NP from alkanes is strong and proceeds to monolayer formation, where the molecules are essentially "upright". However, at high relative concentrations, ethanol successfully out-competes 4NP for the iron oxide surface. Estimates of the enthalpy and entropy of binding of 4NP were found to be exothermic and entropically disfavored. Sum frequency generation vibrational spectroscopy data indicate some evidence of binding through a phenolate anion, despite the nonpolar, nonaqueous solvent. Carvacrol is also found to adsorb as a monolayer where the molecules are lying "flat". The adsorption of ethanol onto iron oxide from dodecane was investigated through the use of quantitative NMR, which is a convenient analytical technique for measuring adsorption isotherms. It was concluded that ethanol does not form adsorbed monolayers on the surface. Instead, it partitions onto the surface as a surface-enhanced local phase separation related to its poor solubility in alkane solvents.B

Social consensus, income policies and unemployment

The original photocopying quality of this item renders some text unreadable. A hard copy is available in UCD Library at GEN 330.08 IR/UN

Periodic ripples on thermally-annealed Graphene on Cu (110) – reconstruction or Moiré pattern?

We have used Ultrahigh Vacuum (UHV) Scanning tunneling microscopy (STM) to investigate the effect of thermal annealing of graphene grown by chemical vapor deposition (CVD) on a Cu(110) foil. We show that the annealing appears to induce a reconstruction of the Cu surface along the [210] direction, with a period of 1.43 nm. Such reconstructions have been ascribed to the tensile strain induced in the Cu surface by its differential thermal expansion relative to the graphene over-layer, but we show that it is in fact a Moiré pattern due to interference between the graphene and the underlying atomic lattice as evidenced by the appearance of an odd-even transition only observed due to mis-orientation of the top layer of a layered crystal. This highlights that the analysis of STM measurements of graphene on metal surfaces should take such interference effects into account and that the graphene-Cu interface is more complex than previously thought

Current at the nanoscale: an introduction to nanoelectronics

This second edition of the book, initially written as an introductory text dealing with how electric currents behave at the nanometer scale, begins with a general description of electric currents at the macroscale. Then by considering the physical lengthscales relevant to electron flow, it is observed how the behavior of currents varies as they approach the nanoscale. A quantum description of electric current is covered as well as its relevance, with particular reference to defects, grain boundaries, tunnelling and atomic contacts, followed by the effects of current flow through nanostructures, including electromigration, of particular relevance for transistor miniaturization. Next, the techniques used to probe currents and voltages at the nanoscale are considered, focusing on scanning-probe microscopy and transport measurements, before considering electronic transport through molecular and single-electron devices. The book will tie together several aspects of current and recent research on the current flow at the nanoscale. Due to the introductory nature of the book, it will not become obsolete quickly, and chapters can be added at will at later stages as new developments arise. Readership: Advanced undergraduates, graduate students and researchers in nanotechnology