Electronic and Geometrical Structure of Phthalocyanines on Surfaces : An Electron Spectroscopy and Scanning Tunneling Microscopy Study

Core- and Valence Photoelectron Spectroscopy (PES), X-ray- and Ultraviolet-Visible Absorption Spectroscopy (XAS and UV-Vis), Scanning Tunneling Microscopy (STM) and Density Functional Theory (DFT) calculations are used to study the electronic and geometrical structure of a class of macro-cyclic molecules, Phthalocyanines (Pc), on surfaces. These molecules are widely studied due to their application in many different fields. Multilayer and monolayer coverages of Iron Phthalocyanine (FePc) and metal-free Phthalocyanine (H2Pc) deposited on different surfaces are investigated in order to get insight in the electronic and geometrical structure of the obtained overlayers, of crucial importance for the understanding of the film functionality. Sublimation of molecular thick films on Si(100) and on conducting glass results in films with molecules mainly oriented with their molecular plane orthogonal to the surface. Ex-situ deposited H2Pc films on conductive glass show different molecular orientation and morphology with respect to the vacuum sublimated films. We study the monolayer adsorption structure of FePc and H2Pc and compare our results with other Pc’s adsorbed on graphite. We find that the molecular unit cell and the superstructure is characteristic for each Pc adsorbed on graphite, even if the geometrical size of the compared molecules is the same. The PE- and XA- spectra of FePc on graphite are essentially identical for the mono- and multilayer preparations, evidencing weak intermolecular and molecular-substrate interactions of van der Waals nature. Furthermore, we characterize Pc’s on InSb (001)-c(8x2). The substrate In rows are observed to be the adsorption site for Pc’s. We find that the growth of the two-dimensional islands of FePc is prolonged in the [-110] direction, in contrast to ZnPc adsorbed on the same substrate at room temperature. We interpret this result as an indication that the adsorption is controlled by the substrate corrugation observed at 70 K

Higher capital requirements and banks’ cost of capital : An empirical study of the Swedish major banks

In the wake of the financial crisis the systemic importance of banks for the stability of the financial system became evident. Finansinspektionen classifies the banks Nordea, Skandinaviska Enskilda Banken, Svenska Handelsbanken and Swedbank as systemically important for the Swedish financial system. The Basel accords strive to increase the resilience of banks and the financial system by imposing stricter regulatory capital requirements. It is debated how these restraints affect the banks’ cost of capital which prompt the first research question of the study: How has the increase in regulation regarding the capital structure of banks affected Sweden’s major banks’ cost of capital? According to Modigliani & Miller a firm’s cost of capital is independent of its capital structure. The second research question is thus: Does the development regarding Sweden’s major bank’s cost of capital align itself with the Modigliani-Miller theorem? The purpose of the study is thus to assess how the increase in regulatory capital requirements have affected the Swedish major banks’ cost of capital and to what extent these developments align with the Modigliani-Miller theorem. The researchers utilizes a quantitative method and collected secondary data for the period 2008 to 2016 to answer the formulated hypotheses which are deduced from the theoretical framework.   The results from the study illustrate significant correlations between increased regulatory capital requirements and the cost of capital. The authors can however not assert the irrelevance of capital structure for the banks’ cost capital but find that reduced tax shields only have modest effects on the banks’ cost of capital

JamSense : Interference and Jamming Classification for Low-power Wireless Networks

Low-power wireless networks transmit at low output power and are hence susceptible to cross-technology interference. The latter may cause packet loss which may waste scarce energy resources by requiring the retransmission of packets. Jamming attacks are even more harmful than cross-technology interference in that they may totally prevent packet reception and hence disturb or even disrupt applications. Therefore, it is important to recognize such jamming attacks. In this paper, we present JamSense. JamSense extends SpeckSense, a system that is able to detect multiple sources of interference, with the ability to classify jamming attacks. As SpeckSense, JamSense runs on resource-constrained nodes. Our experimental evaluation on real hardware shows that JamSense is able to identify jamming attacks with high accuracy while not classifying Bluetooth or WiFi interference as jamming attacks

The adsorption of iron phthalocyanine on graphite: A scanning tunnelling microscopy study

Different adsorption phases of iron phthalocyanine (FePc) on highly oriented pyrolitic graphite (HOPG) have been characterized by scanning tunnelling microscopy (STM). Evaporation of FePc onto the graphite (000 1) surface, kept at room temperature. results in the formation of three-dimensional molecular islands. After annealing to 400 degrees C different two-dimensional features Lire identified. depending on the initial coverage. At low doses. domains with well defined boundaries have been observed, within which molecules tend to organise in chains. At higher coverage, islands exhibiting well-ordered densely-packed square or hexagonal molecular arrangement have been resolved. For the adsorption structures corresponding to one monolayer islands our results show that the molecules adsorb with the molecular plane parallel to the surface. The high resolution STM images allow us to resolve the orientation of single molecules and Subsequently we suggest that the molecular monolayer is stabilized by van der Waals interactions. The characterization of the observed Moire contrast and a comparison with other similar systems underlines the importance of the central metal in the molecule-molecule and molecule-substrate interactions, which govern the molecular adsorption geometry. (c) 2007 Elsevier B.V. All rights reserved

A high pressure x-ray photoelectron spectroscopy experimental method for characterization of solid-liquid interfaces demonstrated with a Li-ion battery system

We report a methodology for a direct investigation of the solid/liquid interface using high pressure x-ray photoelectron spectroscopy (HPXPS). The technique was demonstrated with an electrochemical system represented by a Li-ion battery using a silicon electrode and a liquid electrolyte of LiClO4 in propylene carbonate (PC) cycled versus metallic lithium. For the first time the presence of a liquid electrolyte was realized using a transfer procedure where the sample was introduced into a 2 mbar N-2 environment in the analysis chamber without an intermediate ultrahigh vacuum (UHV) step in the load lock. The procedure was characterized in detail concerning lateral drop gradients as well as stability of measurement conditions over time. The X-ray photoelectron spectroscopy (XPS) measurements demonstrate that the solid substrate and the liquid electrolyte can be observed simultaneously. The results show that the solid electrolyte interphase (SEI) composition for the wet electrode is stable within the probing time and generally agrees well with traditional UHV studies. Since the methodology can easily be adjusted to various high pressure photoelectron spectroscopy systems, extending the approach towards operando solid/liquid interface studies using liquid electrolytes seems now feasible. (C) 2015 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License

A high-pressure x-ray photoelectron spectroscopy instrument for studies of industrially relevant catalytic reactions at pressures of several bars

We present a new high-pressure x-ray photoelectron spectroscopy system dedicated to probing catalytic reactions under realistic conditionsat pressures of multiple bars. The instrument builds around the novel concept of a “virtual cell” in which a gas flow onto the sample surfacecreates a localized high-pressure pillow. This allows the instrument to be operated with a low pressure of a few millibar in the main chamber,while simultaneously a local pressure exceeding 1 bar can be supplied at the sample surface. Synchrotron based hard x-ray excitation is usedto increase the electron mean free path in the gas region between sample and analyzer while grazing incidence <5○ close to total externalrefection conditions enhances surface sensitivity. The aperture separating the high-pressure region from the differential pumping of theelectron spectrometer consists of multiple, evenly spaced, micrometer sized holes matching the footprint of the x-ray beam on the sample.The resulting signal is highly dependent on the sample-to-aperture distance because photoemitted electrons are subject to strong scatteringin the gas phase. Therefore, high precision control of the sample-to-aperture distance is crucial. A fully integrated manipulator allows forsample movement with step sizes of 10 nm between 0 and −5 mm with very low vibrational amplitude and also for sample heating up to500 ○C under reaction conditions. We demonstrate the performance of this novel instrument with bulk 2p spectra of a copper single crystal atHe pressures of up to 2.5 bars and C1s spectra measured in gas mixtures of CO + H2 at pressures of up to 790 mbar. The capability to detectemitted photoelectrons at several bars opens the prospect for studies of catalytic reactions under industrially relevant operando conditions