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1.
The CITIUS light source
Sandra Gardonio, Giovanni De Ninno, Barbara Ressel, 2013, objavljeni povzetek znanstvenega prispevka na konferenci

Najdeno v: ključnih besedah
Povzetek najdenega: ...femtosecond laser source, time resolved photoemission spectroscopy, correlated electron materials, ...
Ključne besede: femtosecond laser source, time resolved photoemission spectroscopy, correlated electron materials
Objavljeno: 06.05.2014; Ogledov: 4750; Prenosov: 23
URL Polno besedilo (0,00 KB)

2.
Chemical and structural investigation of the cobalt phthalocyanine
Matija Stupar, 2015, magistrsko delo

Opis: In the last two decades, studies on organic molecules mimicking substances of fundamental importance in nature, like chlorophyll or hemoglobin, have attracted researchers’ attention. These molecules are building blocks for a family of materials also referred to as “organic semiconductors”. Such compounds can be implemented in numerous applications, ranging from data-storage to light harvesting. Some of their fundamental advantages include low cost, light weight, relatively easy engineering and mechanical flexibility, compatible with bending plastic substrates. In this thesis work we investigated the chemical, structural and electronic properties of cobalt phthalocyanines (CoPc). These molecules have promising applications in the field of magnetic data storage and spintronics in general, due to the ferromagnetic properties of the cobalt atom. Several techniques like photoemission core-level spectroscopy and valence band spectroscopy, together with X-ray absorption, have been used in order to determine the CoPc properties in gaseous phase, i.e. in the absence of interaction with the surrounding environment. Another set of experiments was devoted to the commissioning of the CITIUS time-resolved photoemission setup, that will be used in future studies of CoPc molecules on surfaces.
Najdeno v: ključnih besedah
Povzetek najdenega: ...devoted to the commissioning of the CITIUS time-resolved photoemission setup, that will be used in...
Ključne besede: Cobalt phthalocyanine (CoPc), photoemission spectroscopy (PES), X-ray absorption spectroscopy (XAS), synchrotron radiation, laser, high order harmonic generation (HHG), time resolved spectroscopy
Objavljeno: 29.09.2015; Ogledov: 6405; Prenosov: 235
.pdf Polno besedilo (2,96 MB)

3.
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
Povzetek najdenega: ...the interaction of light with complex organic molecules. Time‐resolved spectroscopies are a new investigation tool that gives...
Ključne besede: self‐assembled monolayer (SAM), surface structures molecular layers, nanotechnology, electronic properties, spectroscopies, time resolved
Objavljeno: 12.06.2017; Ogledov: 2920; Prenosov: 128
.pdf Polno besedilo (5,78 MB)

4.
The role of charge transfer at reduced graphene oxide/organic semiconductor interface on the charge transport properties
Gvido Bratina, Egon Pavlica, 2019, izvirni znanstveni članek

Opis: The effect of 1-pyrenesulfonicacid sodium salt (1-PSA), tetracyanoethylene (TCNE) and tetrafluoro- tetracyanoquinodimethane (F4-TCNQ) on charge transport properties of reduced graphene oxide (RGO) is examined by measuring the transfer characteristics of field-effect transistors and co-planar time-of-flight photocurrent technique. Evidence of p-type doping and a reduction of mobility of electrons in RGO upon deposition of these materials is observed. Time-resolved photocurrent measurements show a reduction in elec- tron mobility even at submonolayer coverage of these materials. The variation of transit time with different coverages reveals that electron mobility decreases with increasing the surface coverage of 1-PSA, TCNE and F4- TCNQ to a certain extent, while at higher coverage the electron mobility is slightly recovered. All three molecules show the same trend in charge carrier mobility variation with coverage, but with different magnitude. Among all three molecules, 1-PSA acts as weak electron acceptor compared to TCNE and F4-TCNQ. The additional fluorine moieties in F4-TCNQ provides excellent electron withdrawing capability compared to TCNE. The experimental results are consistent with the density functional theory calculations.
Najdeno v: ključnih besedah
Povzetek najdenega: ...transfer characteristics of field-effect transistors and co-planar time-of-flight photocurrent technique. Evidence of p-type doping and... ...upon deposition of these materials is observed. Time- resolved photocurrent measurements show a reduction in elec-...
Ključne besede: organic semiconductors, reduced graphene oxide, time-resolved photocurrent measurements, organic thin film transistors
Objavljeno: 28.10.2019; Ogledov: 1691; Prenosov: 1
.pdf Polno besedilo (2,22 MB)

5.
Dissecting Mott and charge-density wave dynamics in the photoinduced phase of 1T-TaS[sub]2
Alberto Simoncig, Matija Stupar, Barbara Ressel, Tanusree Saha, Primož Rebernik Ribič, Giovanni De Ninno, 2021, izvirni znanstveni članek

Opis: The two-dimensional transition-metal dichalcogenide 1T−TaS2 is a complex material standing out for its puzzling low temperature phase marked by signatures amenable to both Mott-insulating and charge-density wave states. Electronic Mott states, coupled to a lattice, respond to coherent optical excitations via a modulation of the lower (valence) Hubbard band. Such dynamics is driven by strong electron-phonon coupling and typically lasts for tens of picoseconds, mimicking coherent structural distortions. Instead, the response occurring at the much faster timescale, mainly dominated by electronic many-body effects, is still a matter of intense research. By performing time- and angle-resolved photoemission spectroscopy, we investigated the photoinduced phase of 1T−TaS2 and found out that its lower Hubbard band promptly reacts to coherent optical excitations by shifting its binding energy towards a slightly larger value. This process lasts for a time comparable to the optical pump pulse length, mirroring a transient change of the onsite Coulomb repulsion energy (U). Such an observation suggests that the correction to the bare value of U, ascribed to the phonon-mediated screening which slightly opposes the Hubbard repulsion, is lost within an interval of a few tens of femtoseconds and can be understood as a fingerprint of electronic states largely decoupled from the lattice. Additionally, these results enforce the hypothesis, envisaged in the current literature, that the transient photoinduced states belong to a sort of crossover phase instead of an equilibrium metallic one.
Najdeno v: ključnih besedah
Povzetek najdenega: ...the response occurring at the much faster timescale, mainly dominated by electronic many-body effects, is... ...of intense research. By performing time- and angle- resolved photoemission spectroscopy, we investigated the photoinduced phase...
Ključne besede: ultrafast phenomena, time resolved photoemission, strongly correlated systems, transition metal dichalcogenide
Objavljeno: 13.04.2021; Ogledov: 697; Prenosov: 0
.pdf Polno besedilo (1,34 MB)

6.
Orbital selective dynamics in Fe-pnictides triggered by polarized pump pulse excitations
Kalobaran Maiti, A. Thamizhavel, Giovanni De Ninno, Jurij Urbančič, Barbara Ressel, Matija Stupar, Primož Rebernik Ribič, Tanusree Saha, Ganesh Adhikary, 2021, izvirni znanstveni članek

Opis: Quantum materials display exotic behaviours related to the interplay between temperature-driven phase transitions. Here, we study the electron dynamics in one such material, CaFe$_2$As$_2$, a parent Fe-based superconductor, employing time and angle-resolved photoemission spectroscopy. CaFe$_2$As$_2$ exhibits concomitant transition to spin density wave state and tetragonal to orthorhombic structure below 170 K. The Fermi surface of this material consists of three hole pockets ($\alpha$, $\beta$ and $\gamma$) around $\Gamma$-point and two electron pockets around $X$-point. The hole pockets have $d_{xy}$, $d_{yz}$ and $d_{zx}$ orbital symmetries. The $\beta$ band constituted by $d_{xz}$/$d_{yz}$ orbitals exhibit a gap across the magnetic phase transition. We discover that polarized pump pulses can induce excitations of electrons of a selected symmetry. More specifically, while $s$-polarized light (polarization vector perpendicular to the $xz$-plane) excites electrons corresponding to all the three hole bands, $p$-polarized light excites electrons essentially from ($\alpha$,$\beta$) bands which are responsible for magnetic order. Interestingly, within the magnetically ordered phase, the excitation due to the $p$-polarized pump pulses occur at a time scale of 50 fs, which is significantly faster than the excitation induced by $s$-polarized light ($\sim$ 200 fs). These results suggest that the relaxation of different ordered phases occurs at different time scales and this method can be used to achieve selective excitations to disentangle complexity in the study of quantum materials.
Najdeno v: ključnih besedah
Povzetek najdenega: ...material, CaFe$_2$As$_2$, a parent Fe-based superconductor, employing time and angle-resolved photoemission spectroscopy. CaFe$_2$As$_2$ exhibits concomit...
Ključne besede: Electronic structure, Pnictides and chalcogenides, Time-resolved spectroscopy
Objavljeno: 13.10.2021; Ogledov: 334; Prenosov: 0
.pdf Polno besedilo (9,56 MB)

7.
Hot-carrier and optical-phonon ultrafast dynamics in the topological insulator Bi2Te3 upon iron deposition on its surface
G De Ninno, K.C. Prince, M Stupar, B Ressel, B Arnaud, V Juvè, G Vaudel, A Ciavardini, T Sobol, K Balin, M Weis, P Ruello, J Szade, 2021, izvirni znanstveni članek

Opis: This paper presents a complete study of electronic structures and photoexcited carrier dynamics in topological insulators capped with iron and iron oxide. We combine static and time-resolved angle-resolved photoemission spectroscopies (ARPES, TR-ARPES) with time-resolved optical methods (transient optical reflectivity and transmission). Both single crystal and thin films of Bi2Te3 are studied. We show that monolayers of iron and iron oxide significantly affect the electronic band structure at the interface by shifting the Fermi level into the conduction band, which we explain by a band bending effect, and is confirmed by in situ XPS measurements
Najdeno v: ključnih besedah
Povzetek najdenega: ...and iron oxide. We combine static and time-resolved angle-resolved photoemission spectroscopies (ARPES, TR-ARPES) with time-resolve...
Ključne besede: time resolved spectroscopies, topological insulators, interfaces
Objavljeno: 13.12.2021; Ogledov: 127; Prenosov: 0
.pdf Polno besedilo (2,90 MB)

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