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1.
Introduction to Electronic Properties and Dynamics of Organic Complexes as Self‐Assembled Monolayers
Maddalena Pedio, 2017, samostojni znanstveni sestavek ali poglavje v monografski publikaciji

Opis: Self‐assembled monolayers (SAMs) of organic‐conjugated transition metal complexes on surfaces is a focus of both device engineering and basic science, since it is a key factor in nearly all important aspects of device performances, including operation voltages, degradation, and efficiency. The huge amount of literature results related to the first monolayer, and reorganization and self‐assembling processes are due to the general accepted result that structural and chemical properties of the first monolayer are the key parameters for controlled thin film growth. Optical and magneto‐electronic properties are intimately connected, and the accurate determination of electronic levels, excitation, and relaxation dynamics is mandatory for the optimization of electronic, photovoltaic, and opto‐electronic devices. Quite a number of electronic states is generated by the interaction of light with complex organic molecules. Time‐resolved spectroscopies are a new investigation tool that gives the possibility of correctly addressing their origin and life time. Examples of prototypical systems are presented and discussed. We review on complementary techniques, trying to single out how different approaches are fundamental to fully characterize these complex systems.
Najdeno v: ključnih besedah
Ključne besede: self‐assembled monolayer (SAM), surface structures molecular layers, nanotechnology, electronic properties, spectroscopies, time resolved
Objavljeno: 12.06.2017; Ogledov: 1879; Prenosov: 97
.pdf Polno besedilo (5,78 MB)

2.
Growth, morphology and stability of Au in contact with the Bi[sub]2Se[sub]3(0 0 0 1) surface
Mattia Fanetti, I. Mikulska, Katja Ferfolja, Paolo Moras, P. M. Sheverdyaeva, M. Panighel, A. Lodi-Rizzini, I. Píš, S. Nappini, Matjaž Valant, Sandra Gardonio, 2018, izvirni znanstveni članek

Najdeno v: ključnih besedah
Povzetek najdenega: ...metal contact, topological insulator contact, growth mode, electronic properties, chemical properties, photoemission spectroscopy, microscopy...
Ključne besede: metal contact, topological insulator contact, growth mode, electronic properties, chemical properties, photoemission spectroscopy, microscopy
Objavljeno: 05.12.2018; Ogledov: 895; Prenosov: 0
.pdf Polno besedilo (8,13 MB)

3.
Au and Ag on the Bi2Se3(0001) Surface: Experimental Electronic and Physical Properties
Sandra Gardonio, Mattia Fanetti, Katja Ferfolja, Matjaž Valant, objavljeni povzetek znanstvenega prispevka na konferenci

Opis: Binary bismuth chalcogenides, Bi2Se3 and Bi2Te3, have been extensively studied as reference topological insulators (TIs). These materials are bulk insulators with topological surface states (TSS) crossing the Fermi level. In contrast to conventional surface states of metals, the TSS are extremely robust against local modifications at the surface, such as adsorbed adatoms, localized defects or changes in the surface termination. This aspect makes the TIs attractive for applications in spintronics, plasmonics, quantum computing and catalysis. A theoretical model of charge transport by the TI surface states predicts that the TSS survive, provided that bonding at the metal/TI interface is weak. Ab-initio calculations have been done to understand the electronic properties of Au, Ni, Pt, Pd and graphene layers in a contact with Bi2Se3. These calculations showed that for Au and graphene the spin-momentum locking of TSS is maintained at the interface. In another theoretical study, Ag and Au thin layers on Bi2Se3 have been predicted to show a large Rashba splitting and a high spin polarization of the Ag quantum wells, providing a great potential for development of the spintronic devices. Finally, the calculations have foreseen that the presence of the robust TSS affects the adsorption properties of metals (Au bi-layer and clusters of Au, Ag, Cu, Pt, and Pd) supported on TI, in some cases resulting in the enhancement of the catalytic processes. Despite the fundamental importance of the metal/TI interfaces and a number of theoretical studies predicting exotic interfacial phenomena, the experimental knowledge about the metals on the TI surfaces is surprisingly limited, especially concerning combined study of morphology, growth mode, electronic and chemical properties. In order to exploit the predicted physical properties of such systems, it is especially important to extend the study above the diluted coverage regime and to understand what is the growth morphology of the metal on the TI surface, to what extent the metal overlayer interacts with the TI substrate, how the TSS change with the presence of the metal overlayer and what is the reactivity of the system at the different stages of the overlayer growth. Within this frame, we present a comprehensive surface sensitive study, of Au and Ag on Bi2Se3 by means of ARPES, XPS, SEM, LEED and XRD. The obtained results allow us to discuss the relation between electronic and physical properties at two of the most important model metal/TI interfaces
Najdeno v: ključnih besedah
Ključne besede: topological insulator, electronic properties, synchrotron radiation
Objavljeno: 27.06.2019; Ogledov: 771; Prenosov: 0
.pdf Polno besedilo (5,72 MB)

4.
Looking for a topological insulator in the tetradymite family
Matjaž Valant, Paolo Moras, P. M. Sheverdyaeva, Mattia Fanetti, Zipporah Rini Benher, Sandra Gardonio, 2019, objavljeni povzetek znanstvenega prispevka na konferenci

Opis: Materials that are topological insulators (TI) manifest a novel state for their electrons. They possess topological surface states that are not destroyed by the presence of non-magnetic impurities on their surfaces. This unique property lies in the bulk band structure and it is typically found in narrow gap semiconductor with strong spin-orbit coupling. Bi2Se3 and Bi2Te3 belong to the class of compounds called tetradymites and are considered as the 3D-prototypical TI materials. However, these compounds are not usually insulators but have metallic bulk conductivity as a consequence of intrinsic defect doping: vacancies and anti-site defects. For these reasons, it is difficult to electrically gate these materials for the manipulation and control of charge carriers for realizing devices. This led to the search for other topological materials, which might have better insulating behavior in their bulk. Theoretical studies have pointed out that ternary variants of the Bi2Se3 and Bi2Te3, such as Bi2Te2Se, Bi2Te2S, Bi2Se2S Sb2Te2Se and Sb2Te2S, should be stable TIs and potentially offer a chemical way to control TI behavior, in particular by lowering native doping. Among the cited ternary compounds, Bi2Se2S should manifest a genuine topological spin-transport regime hosting an isolated Dirac cone with the Dirac point in the gap as well. However, it has been poorly studied from the TI experimental perspective. Therefore, to uncover the full potential of the predicted topological electronic properties of the Bi-Se-S system, in this presentation we will revisit the crystallographic and electronic structure of Bi2Se3-Bi2S3 solid solutions. The combined use of bulk and surface sensitive techniques such as X-ray diffraction (XRD), low energy electron diffraction (LEED), scanning electron microscopy (SEM) with Energy Dispersive X-ray spectroscopy (EDX) and X-ray photoemission spectroscopy (XPS) was applied to analyze single crystal samples grown by us. The quality of the single crystals was suitable for rigorous measurement of the electronic properties by means of Angle Resolved Photoemission Spectroscopy. We unambiguously showed that within a certain solid solution range, the single crystals of Bi-Se-S have a rombohedral structure with the topological surface states as theoretically predicted.
Najdeno v: ključnih besedah
Povzetek najdenega: ...the full potential of the predicted topological electronic properties of the Bi-Se-S system, in this...
Ključne besede: topological insulators, ternary tetradymite, electronic properties.
Objavljeno: 19.12.2019; Ogledov: 707; Prenosov: 0
.pdf Polno besedilo (6,45 MB)

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