The local structure of OH species on the V2O3(0 0 0 1) surface: a scanned-energy mode photoelectron diffraction study

Scanned-energy mode photoelectron diffraction (PhD), using O 1s photoemission, together with multiple-scattering simulations, have been used to investigate the structure of the hydroxyl species, OH, adsorbed on a V2O3(0 0 0 1) surface. Surface OH species were obtained by two alternative methods; reaction with molecular water and exposure to atomic H resulted in closely similar PhD spectra. Both qualitative assessment and the results of multiple-scattering calculations are consistent with a model in which only the O atoms of outermost layer of the oxide surface are hydroxylated. These results specifically exclude significant coverage of OH species atop the outermost V atoms, i.e. in vanadyl O atom sites. Ab initio density-functional theory cluster calculations provide partial rationalisation of this result, which is discussed the context of the general understanding of this system

Growth and properties of strained VOx thin films with controlled stoichiometry

We have succeeded in growing epitaxial films of rocksalt VOx on MgO(001) substrates. The oxygen content as a function of oxygen flux was determined using 18O2-RBS and the vanadium valence using XAS. The upper and lower stoichiometry limits found are similar to the ones known for bulk material (0.8<x<1.3). From the RHEED oscillation period a large number of vacancies for both vanadium and oxygen were deduced, i.e. ~16% for stoichiometric VO. These numbers are, surprisingly, very similar to those for bulk material and consequently quite strain-insensitive. XAS measurements reveal that the vacancies give rise to strong low symmetry ligand fields to be present. The electrical conductivity of the films is much lower than the conductivity of bulk samples which we attribute to a decrease in the direct overlap between t2g orbitals in the coherently strained layers. The temperature dependence of the conductivity is consistent with a variable range hopping mechanism.Comment: 12 pages, 16 figures included, revised versio

Über planare Graphen

Im Laufe des 20. Jahrhunderts hat sich das Gebiet der Graphentheorie zu einer allgemein anerkannten Disziplin der Mathematik entwickelt. Graphen sind spezielle Konstrukte, welche aus Punkten sowie Verbindungsstrecken zwischen diesen Punkten bestehen; sie werden etwa zur Modellierung in der Informationstechnologie, der Logistik und anderen Gebieten herangezogen. Diese Arbeit beschäftigt sich mit einer Subgattung von Graphen, nämlich jener der planaren Graphen. Dies sind Graphen, welche derart visualisiert werden können, dass keinerlei Überkreuzungen der zugehörigen Verbindungsstrecken auftreten. Der Fokus liegt hierbei einerseits auf der Theorie planarer Graphen, welche unter anderem den Eulerschen Polyedersatz, den Satz von Kuratowski, Dualität sowie Färbung umfasst. Andererseits wird ein Algorithmus besprochen, welcher eine planare Einbettung eines beliebigen Graphen konstruiert, sofern dies möglich ist.During the last century the field of graph theory has become a widely accepted discipline in mathematics. Graphs are specific constructs which consist of points and connecting lines (or arcs) between these points. They find application in various fields, where modelling in both IT and logistics deserves special mention. This thesis deals with a subclass of graphs, namely planar graphs. These are graphs which can be visualised in a way to avoid any crossings of lines/arcs. On the one hand, the focus lies on the theory of planar graphs which, e. g., covers Euler's formula, Kuratowski's theorem, duality and colouring. On the other hand, an algorithm will be discussed which constructs some planar embedding of an arbitrary graph, in case this is possible.Autor: Harald LeisenbergerAbweichender Titel laut Übersetzung des Verfassers/der VerfasserinZusammenfassungen in Deutsch und EnglischKarl-Franzens-Universität Graz, Diplomarbeit, 2017(VLID)206217

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"užsienietis", [email protected] Didžiojo universiteta

Evidence of erratic behaviors in p-channel floating gate memories and cell architectural solution

This work shows for the first time the presence of erratic phenomena in p-channel floating gate memories using Fowler Nordheim tunneling for both program and erase operations. A specific p-channel EEPROM architecture is investigated and found to be intrinsically robust against erratic behaviors. A comparison between the p-channel device and a conventional n-channel Flash is discussed and physical interpretations are suggested