Surface Termination (surface + termination)

Distribution by Scientific Domains


Selected Abstracts


The Influence of Doping Levels and Surface Termination on the Electrochemistry of Polycrystalline Diamond

ELECTROANALYSIS, Issue 6 2004
Matthew
Abstract The influence of surface chemistry and boron doping density on the redox chemistry of Fe(CN) at CVD polycrystalline diamond electrodes is considered. It is demonstrated that for this couple both the doping density and the surface chemistry are important in determining the rate of charge transfer at the electrode/electrolyte interface. For hydrogen terminated CVD diamond metallic electrochemical behavior is always observed, even at boron doping densities as low as 7×1018,cm,3. In contrast, the electrochemical behavior of oxygen terminated CVD diamond varies with doping density, a metallic response being observed at high doping density and semiconductor behavior at low doping density. It is shown that the results attained may be explained by a surface state mediated charge transfer mechanism, thus demonstrating the importance of controlling surface chemistry in electroanalytical applications of diamond. [source]


Real-Space Observation of Surface Termination of a Complex Metal Oxide Catalyst,

ANGEWANDTE CHEMIE, Issue 35 2010
Wei Zhang Dr.
Schöner Anblick: Hochauflösungs-TEM kann genutzt werden, um die Oberflächenstruktur eines Metalloxid-Katalysators im Realraum zu bestimmen. Das Bild zeigt HR-TEM-Aufnahmen eines einzelnen Katalysatorpartikels entlang ,001,-Richtung weit entfernt vom Scherzer-Fokus. Der Partikelumfang wird durch die frakturierten Struktureinheiten verdeutlicht. [source]


Oxygen-Terminated Nanocrystalline Diamond Film as an Efficient Anode in Photovoltaics

ADVANCED FUNCTIONAL MATERIALS, Issue 8 2010
Candy Haley Yi Xuan Lim
Abstract The potential of using p-doped nanocrystalline diamond as the anode for organic solar cells, because of its outstanding photostability and well-matched energetics with organic dyes, is demonstrated. The interface dipole and open-circuit potential can be tuned by varying the surface termination on diamond. Oxygenated nanocrystalline diamond (O-NCD) exhibits the best photocurrent conversion among all the surface-treated electrodes studied in this work because of its large open-circuit potential. The good energy alignment of the valence band of O-NCD with the HOMO of poly(3-hexylthiophene), as well as its p-doped characteristics, suggest that O-NCD can replace the hole transport layer, such as PEDOT:PSS, needed for efficient performance on indium tin oxide (ITO) electrodes. If the sheet resistance and optical transparency on NCD can be further optimized, chemical-vapor-deposited diamond electrodes may offer a viable alternative to ITO and fluorinated tin oxide (FTO). [source]


Engineering the line up of electronic energy levels at inorganic,organic semiconductor interfaces by variation of surface termination and by substitution

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 9 2008
Thomas Mayer
Abstract In the Anderson model the alignment of electronic energy levels follows from the assumption that the vacuum-levels of the contacting phases are at equal height. Engineering of the line up may be attempted by changing the ionization energy of the substrate and/or of the adsorbate. We report on the variation of the Si(111) ionization energy by induced surface dipoles of ,CH3, ,H, and ,GaSe terminations and the induced variation of the HOMO line up of PTCDA and ZnPc layers. In addition the variation of the line up by changing the organic molecule ionization energy is exemplified by F substitution in ZnPc. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Inhomogeneous surface electronic properties and charge ordering in epitaxial Fe3O4 films on MgO(001)

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 12 2007
A. Subagyo
Abstract We report scanning tunneling microscopy (STM) study of surface electronic properties and charge ordering of epitaxially grown magnetite, Fe3O4, (001) films exhibiting high density of antiphase domain boundaries (APBs). STM measurements using a W tip reveal surface termination at B-sites. Fe ions with a 0.3 nm periodicity, i.e., a single atomic distance are observed. Current imaging tunneling spectroscopy reveals the alternation of two kinds of current peaks with a 0.6 nm periodicty indicating the presence of charge ordering consisted of Fe dimers with different charge states. STM measurements using a magnetic Ni tip provide higher contrast of the charge ordering. The APBs can modify the charge ordering as ordered and disordered areas are observed on adjacent domains separated by an APB. These strongly indicate that APBs can induce inhomogeneous properties on the surface of Fe3O4(001) films. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Microscopic diagnostics of DNA molecules on mono-crystalline diamond

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 9 2007
Bohuslav Rezek
Abstract Detailed data about deoxyribonucleic acid (DNA) attachment, arrangement, density and functionality on mono-crystalline diamond surfaces are obtained by direct measurements in electrolytic solutions using fluorescence microscopy and atomic force microscopy in various regimes (oscillating, contact, phase, and surface potential imaging) and by fitting the data into a microscopic geometrical model of DNA. DNA is immobilized on undoped and boron-doped diamonds with hydrogen and oxygen surface terminations which were functionalized by aminodecene and nitrofenyl linker molecules. The data show that, except photochemically processed oxidized diamond surfaces, the DNA molecules are covalently linked to diamond in a 65,92 Å thin and highly dense layers (6 × 1012 molecules/cm2) with sub-nanometer intermolecular spacing and a strong tilt of 31° with respect to the surface. Ordering of these DNA layers shows only a weak (<10%) response to a change of buffer salinity in the range of 1,300 mM. The data are discussed with view to biosensor applications. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Density functional study of graphene overlayers on SiC

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 7 2008
Alexander Mattausch
Abstract Despite the ongoing "graphene boom" of the last three years our understanding of epitaxial graphene grown on SiC substrate is only beginning to emerge. Along with experimental methods such as low energy electron diffraction (LEED), scanning tunneling microscopy (STM) and angle resolved photoemission spectroscopy (ARPES), ab initio calculations help to uncover the geometric and electronic structure of the graphene/SiC interface. In this chapter we describe the density-functional calculations we performed for single and double graphene layers on Si- and C-terminated 6H-SiC surfaces. Experimental data reveal a pronounced difference between the two surface terminations. On a Si-terminated surface the interface adopts a 6,3 × 6,3 unit cell whereas the C-face supports misoriented (turbostratic) graphene layers. It has been recently realized that, on the Si-face, the large commensurate cell is subdivided into patches of coherently matching to the substrate carbon atoms. In our calculations we assumed the "coherent match" geometry for the whole interface plane. This reduces the periodic unit to the ,3 × ,3R 30° cell but requires a substantial stretching of the graphene sheet. Although simplified, the model provides a qualitative picture of the bonding and of the interface electron energy spectrum. We find that the covalent bonding between the carbon layer and the substrate destroys the massless "relativistic" electron energy spectrum, the hallmark of a freestanding graphene. Hence the first carbon layer cannot be responsible for the graphene-type electron spectrum observed by ARPES and rather plays a role of a buffer between the substrate and the subsequent carbon sheets. The "true" graphene spectrum appears with the second carbon layer which exhibits a weak van der Waals bonding to the underlying structure. For Si-terminated substrate, we find that the Fermi level is pinned by the interface state at 0.45 eV above the graphene Dirac point, in agreement with experimental data. This renders the interface metallic. On the contrary, for a C-face the "coherent match" model predicts the Fermi level exactly at the Dirac point. However, this does not necessarily apply to the turbostratic graphene layers that normally grow on the C-terminated substrate. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]