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62. Fractal and inertia moment analyses for thin film quality monitoringMohanachandran Nair Sindhu Swapna, 2022, izvirni znanstveni članek Opis: The widespread applications of thin films in optronics demand innovative techniques for its characterizations. The work reported here proposes electronic speckle pattern interferometry and fractal-based methods for assessing the quality of thin films taking the industrially relevant molybdenum oxide (MoO3) incorporated niobium oxide (Nb2O5) films. The films with different levels of MoO3 incorporation (1, 2, 3, 5, and 10 wt. %) are prepared by radio frequency sputtering. The study reveals the structure modifications of Nb2O5 from the orthorhombic to monoclinic phases with an associated morphological variation revealed through atomic force microscopy and field-emission scanning electron microscopy analyses. The films’ specklegrams are recorded under thermal stress; the inertia moment (IM) and fractal analyses are computed and compared with the root-mean-square surface roughness of the films. The lacunarity analysis of the AFM films agrees well with the specklegrams. Thus, the lower IM and lacunarity values of the specklegrams can be regarded as indicators of the good quality of thin films.
Ključne besede: cross-correlation, fractal dimension, inertia moment, lacunarity, speckle, surface roughness.
Objavljeno v RUNG: 30.06.2022; Ogledov: 1934; Prenosov: 0
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63. Silica coated Bi[sub]2Se[sub]3 topological insulator nanoplatelets : the way of making them colloidally stable but preserving their optical propertiesBlaž Belec, Nina Kostevšek, Sebastjan Nemec, Slavko Kralj, Sandra Gardonio, Mattia Fanetti, Matjaž Valant, 2021, objavljeni povzetek znanstvenega prispevka na konferenci Ključne besede: topological insulator, optical properties, topological surface states, silica-coated
Objavljeno v RUNG: 27.09.2021; Ogledov: 3220; Prenosov: 0
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64. Room-temperature solid-state reaction at the Ag/Bi[sub]2Se[sub]3 interfaceKatja Ferfolja, Mattia Fanetti, Iuliia Mikulska, Sandra Gardonio, Matjaž Valant, 2017, objavljeni povzetek znanstvenega prispevka na konferenci Opis: Topological insulators (TI) are materials that, while having a forbidden bandgap in bulk, are conductors at their surface due to presence of surface-localized electronic states crossing the band gap. [1] TIs are possible because of a time reversal symmetry and spin-orbit coupling, which invert bulk band states in their energy positions and make the bulk band structure non trivial. Consequently, the topological surface states (TSS) emerge on the surface of these materials. Unlike ordinary surface states, TSS cannot be destroyed by contamination or defects on the surface. Additionally, TSS are also spin polarized, which means that when applying current to TI, the current will have a well defined direction of the electron spins.
The topological insulators - a relatively new class of materials - are being widely studied not only from fundamental aspects, but also from their applicative perspectives. It has been predicted that TIs could be used in fields of spintronics, electronics and catalysis. [2,3] Interestingly, only a few studies about metal/TI interfaces have been reported. This is surprising since integration of TI in the applications will often necessitate an interface with the metal, therefore, detailed knowledge on chemistry and electrical conditions at the interface will be required.
In this contribution results on research on the chemistry of the Ag/Bi2Se interface will be presented, in particularonthesolid-statereactionbetweennanoparticles.IthasbeenobservedthatwhenBi2Se3 andAgare put in contact a chemical reaction occurs at the interface, producing AgBiSe2 and Ag2Se. Interestingly, the reaction already occurs at room temperature, which is not usual for solid-state reactions. In literature this reaction has not been properly described. The authors rather described it as intercalation of the silver atoms, which we have disproved and showed that recrystallization of the new phases occurs. [3,4,5] The results will alsobediscussedincomparisonwithothertwoAg/Bi2Se3 systemsunderourinvestigation:i)Agdepositedby achemicalrouteonBi2Se3 nanoflakesandii)AgdepositedfromavapourphaseinvacuumonaBi2Se3.single crystal
Ključne besede: topological insulators, topological surface states, solid-state reaction, TI/metal interface
Objavljeno v RUNG: 20.08.2021; Ogledov: 2786; Prenosov: 0
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65. Structural, morphological and chemical properties of metal/topological insulator interfaces : dissertationKatja Ferfolja, 2021, doktorska disertacija Opis: 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
i
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.
Ključne besede: topological insulators, topological surface states, Bi2Se3, thin films, Ag, Ti, Pt, morphology, interfaces, solid-state reaction, metal selenides, reactivity, stability, electron microscopy, dissertations
Objavljeno v RUNG: 09.06.2021; Ogledov: 4968; Prenosov: 186
 Povezava na celotno besedilo
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66. Nitrate as a probe of cytochrome c surface : crystallographic identification of crucial "hot spots" for protein-protein recognitionMatteo De March, Nicola Demitri, Rita De Zorzi, Angela Casini, Chiara Gabbiani, Annalisa Guerri, Luigi Messori, Silvano Geremia, 2014, izvirni znanstveni članek Ključne besede: cytochrome c, electron transfer complexes, electrostatic surface, redox protein
Objavljeno v RUNG: 03.03.2021; Ogledov: 2809; Prenosov: 0
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67. Analysis of Data from Surface Detector Stations of the AugerPrime UpgradeÁlvaro Taboada, Andrej Filipčič, Gašper Kukec Mezek, Samo Stanič, Marta Trini, Serguei Vorobiov, Lili Yang, Danilo Zavrtanik, Marko Zavrtanik, Lukas Zehrer, 2019, objavljeni znanstveni prispevek na konferenci Ključne besede: Pierre Auger Observatory (PAO), ultra-high energy cosmic rays, AugerPrime upgrade of the PAO, Scintillator Surface Detector (SSD), Water-Cherenkov Detectors (WCDs), AugerPrime data analysis
Objavljeno v RUNG: 21.12.2020; Ogledov: 3047; Prenosov: 67
 Celotno besedilo (2,56 MB) |
68. Estimating the Depth of Shower Maximum using the Surface Detectors of the Pierre Auger ObservatoryCarlos José Todero Peixoto, Andrej Filipčič, Gašper Kukec Mezek, Samo Stanič, Marta Trini, Serguei Vorobiov, Lili Yang, Danilo Zavrtanik, Marko Zavrtanik, Lukas Zehrer, 2019, objavljeni znanstveni prispevek na konferenci Ključne besede: Pierre Auger Observatory, ultra-high energy cosmic rays (UHECR), extensive air showers, Auger Surface Detector (SD) array, depth
of shower maximum
Objavljeno v RUNG: 21.12.2020; Ogledov: 2898; Prenosov: 68
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69. Bounds on diffuse and point source fluxes of ultra-high energy neutrinos with the Pierre Auger ObservatoryFrancisco Pedreira, Andrej Filipčič, Gašper Kukec Mezek, Samo Stanič, Marta Trini, Serguei Vorobiov, Lili Yang, Danilo Zavrtanik, Marko Zavrtanik, Lukas Zehrer, 2019, objavljeni znanstveni prispevek na konferenci Ključne besede: Pierre Auger Observatory, Auger Surface Detector, search for ultra-high energy (UHE) neutrinos, upper limits on diffuse and point source UHE neutrino fluxes
Objavljeno v RUNG: 21.12.2020; Ogledov: 3018; Prenosov: 69
Celotno besedilo (447,71 KB) |
70. Analysis of Data from the Low-Energy Modes of the Surface Detector of the Pierre Auger ObservatoryMartin Schimassek, Andrej Filipčič, Gašper Kukec Mezek, Samo Stanič, Marta Trini, Serguei Vorobiov, Lili Yang, Danilo Zavtranik, Marko Zavrtanik, Lukas Zehrer, 2019, objavljeni znanstveni prispevek na konferenci Ključne besede: Pierre Auger Observatory, Surface Detector, Low-Energy Modes
Objavljeno v RUNG: 21.12.2020; Ogledov: 2749; Prenosov: 75
Celotno besedilo (919,66 KB) |
