21. The role of substrate on thermal evolution of Ag/TiO[sub]2 nanogranular thin filmsVincenzo Balzano, Emanuele Cavaliere, Mattia Fanetti, Sandra Gardonio, Luca Gavioli, 2021, original scientific article Keywords: nanogranular composite thin film, substrate driven properties, morphology, optical absorption, Ag/TiO2 Published in RUNG: 03.12.2021; Views: 1783; Downloads: 135 Link to full text This document has many files! More... |
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23. Structural, morphological and chemical properties of metal/topological insulator interfaces : dissertationKatja Ferfolja, 2021, doctoral dissertation Abstract: Topological insulators (TIs) represent a new state of matter that possess a different band structure than regular insulators or conductors. They are characterized with a band gap in the bulk and conductive topological states on the surface, which are spin polarized and robust toward contamination or deformation of the surface. Since the intriguing properties of the TIs are localized at the surface, it is important to obtain knowledge of the possible phenomena happening at the interface between TIs and other materials. This is especially true in the case of metals, due to the fact that such interfaces will be present in the majority of foreseen TI applications.
The presented study combines microscopy and spectroscopy techniques for characterization of morphology, stability and chemical interaction at the interface between TI and metals deposited by means of physical vapor deposition. Our research is based on the interface of Bi2Se3 topological insulator with Ag, Ti and Pt – metals that can be encountered in devices or applications predicted to utilize the special properties of topological insulators.
STM and SEM imaging of Ag/Bi2Se3 interface showed that Ag atoms arrange on the surface in the form of islands, whereas significantly bigger agglomerates are found at the surface steps. The interface was found to be unstable in time and resulted in the absorption of the metal into the crystal at room temperature. Evidences of a chemical reaction at the Ag/Bi2Se3 interface are presented, showing that new phases (Ag2Se, AgBiSe2 and metallic Bi) are formed.
Deposition of Ti on Bi2Se3 resulted in different morphologies depending on the film thickness. At a very low coverage (<1 Å) islands are formed. However, the islands growth is hindered before the completion of a full layer due to the occurrence of a chemical reaction. No surface features could be detected by SEM for Ti coverage up to 20 nm. In contrary, when Ti thickness reached 40 nm, compressive stress triggered buckling of the deposited film. XPS analysis revealed that a redox solid-state reaction occurs at the Ti/Bi2Se3 interface at room temperature forming titanium selenides and metallic Bi. The reaction has significant kinetics even at cryogenic temperature of 130 K.
Pt forms a homogenous film over the whole substrate surface, which is stable in time at room temperature. Although the interface of Pt with Bi2Se3 was found to be
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less reactive compared to Ag and Ti, an interfacial phase formed upon annealing to ∼90 °C was detected by TEM cross section experiment.
A model for prediction of interfacial reactions between a metal and Bi2Se3 based on the standard reduction potential of the metals and Gibbs free energy for a model reaction is presented. Based on these two values the reaction can be expected to result in the formation of binary and/or ternary selenides and Bi.
Presented work shows on the importance of metal/topological insulator interfaces characterization taking into account the possibility of a chemical reaction with all of its consequences. Results should be considered for future theoretical and applicative studies involving such interfaces as well as for the possible engineering of 2D TI heterostructures. Keywords: topological insulators, topological surface states, Bi2Se3, thin films, Ag, Ti, Pt, morphology, interfaces, solid-state reaction, metal selenides, reactivity, stability, electron microscopy, dissertations Published in RUNG: 09.06.2021; Views: 3667; Downloads: 173 Link to full text This document has many files! More... |
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25. Do Slavic secondary imperfectives contain multiple theme vowels?Stefan Milosavljević, Marko Simonović, Boban Arsenijević, Petra Mišmaš, Franc Marušič, Rok Žaucer, 2021, published scientific conference contribution abstract Keywords: Slavic, morphology, secondary imperfectives, theme vowels Published in RUNG: 17.05.2021; Views: 1997; Downloads: 62 Link to full text This document has many files! More... |
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28. Why kl~kolj, br~ber, v~ved, but never kl~br or kolj~ber? : restrictions on the phonological shape of root allomorphs in SlovenianPetra Mišmaš, Marko Simonović, 2021, published scientific conference contribution abstract Keywords: Slovenian, phonology, morphology, verbs, root allomorphy, theme vowels Published in RUNG: 29.01.2021; Views: 2260; Downloads: 69 Link to full text This document has many files! More... |
29. √ov Is in the Air: The Extreme Multifunctionality of the Slovenian Affix ovMarko Simonović, Petra Mišmaš, 2020, original scientific article Abstract: In this paper we consider several instances of the Slovenian affix ov, which surfaces in many, apparently unrelated contexts. Here we focus on (i) ov in verbs, where it can act as an imperfectivizer or a verbalizer, (ii) ov found in possessive adjectives and kind adjectives derived from nouns, (iii) ov which precedes the adjectiviser (e)n in denominal adjectives, and (iv) ov in nominal declension (acting as a genitive case ending in dual and plural or as a dual/plural augment). Building on the observation that certain affixes function either as inflectional or as derivational (see Simonović and Arsenijević 2020), and working within a Distributed Morphology approach which postulates that derivational affixes should be analyzed as roots (e.g. Lowenstamm 2014), we argue for a single multifunctional ov. This ov is a potentially meaningless root that can take as a complement other roots (thus forming a “radical core”) or phrases, resulting in different structures and consequently different stress patterns and meanings, but can also act as an Elsewhere allomorph, whose insertion is guided by an interplay of phonological and morphological constraints. Keywords: morphology, Distributed Morphology, Slovenian, multifunctional affix, roots Published in RUNG: 04.01.2021; Views: 2188; Downloads: 64 Full text (609,55 KB) |
30. Effect of the Morphology of the High-Surface-Area Support on the Performance of the Oxygen-Evolution Reaction for Iridium NanoparticlesLeonard Moriau, Marjan Bele, Živa Marinko, Francisco Ruiz-Zepeda, Gorazd Koderman, Martin Šala, Angelija Kjara Šurca, Janez Kovač, Iztok Arčon, Primož Jovanovič, Nejc Hodnik, Luka Suhadolnik, 2021, original scientific article Abstract: The development of affordable, low-iridium-loading,
scalable, active, and stable catalysts for the oxygen-evolution
reaction (OER) is a requirement for the commercialization of
proton-exchange membrane water electrolyzers (PEMWEs).
However, the synthesis of high-performance OER catalysts with
minimal use of the rare and expensive element Ir is very challenging
and requires the identification of electrically conductive and stable
high-surface-area support materials. We developed a synthesis
procedure for the production of large quantities of a nanocomposite
powder containing titanium oxynitride (TiONx) and Ir.
The catalysts were synthesized with an anodic oxidation process
followed by detachment, milling, thermal treatment, and the
deposition of Ir nanoparticles. The anodization time was varied to grow three different types of nanotubular structures exhibiting different lengths and wall thicknesses and thus a variety of properties. A comparison of milled samples with different degrees of nanotubular clustering and morphology retention, but with identical
chemical compositions and Ir nanoparticle size distributions and dispersions, revealed that the nanotubular support morphology is
the determining factor governing the catalyst’s OER activity and stability. Our study is supported by various state-of-the-art
materials’ characterization techniques, like X-ray photoelectron spectroscopy, scanning and transmission electron microscopies, Xray powder diffraction and absorption spectroscopy, and electrochemical cyclic voltammetry. Anodic oxidation proved to be a very suitable way to produce high-surface-area powder-type catalysts as the produced material greatly outperformed the IrO2 benchmarks
as well as the Ir-supported samples on morphologically different TiONx from previous studies. The highest activity was achieved for the sample prepared with 3 h of anodization, which had the most appropriate morphology for the effective removal of oxygen
bubbles. Keywords: electrocatalysis, oxygen-evolution reaction, TiONx-Ir powder catalyst, iridium nanoparticles, anodic oxidation, morphology−activity correlation Published in RUNG: 04.01.2021; Views: 2537; Downloads: 0 This document has many files! More... |