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11.
Ultra-Fast-VUV Photoemission Study of UV Excited 2-Nitrophenol
A. Ciavardini, Marcello Coreno, Carlo Callegari, C. Spezzani, Giovanni De Ninno, Barbara Ressel, Cesare Grazioli, Monica de Simone, Antti Kivimak̈i, Paolo Miotti, Fabio Frassetto, Luca Poletto, Petra Rudolf, Simona Fornarini, Marco Pezzella, Enrico Bodo, Susanna Piccirillo, 2019, original scientific article

Abstract: The initial deactivation pathways of gaseous 2-nitrophenol excited at 268 nm were investigated by time-resolved photoelectron spectroscopy (TRPES) with femtosecond-VUV light, produced by a monochromatized high harmonic generation source. TRPES allowed us to obtain new, valuable experimental information about the ultrafast excited-state dynamics of 2-nitrophenol in the gas phase. In accord with recent ab initio on-the-fly nonadiabatic molecular dynamic simulations, our results validate the occurrence of an ultrafast intersystem crossing leading to an intermediate state that decays on a subpicosecond time scale with a branched mechanisms. Two decay pathways are experimentally observed. One probably involves proton transfer, leading to the most stable triplet aci-form of 2-nitrophenol; the second pathway may involve OH rotation. We propose that following intersystem crossing, an ultrafast fragmentation channel leading to OH or HONO loss could also be operative.
Keywords: Ultrafast photoemission, nitrophenol
Published in RUNG: 12.02.2019; Views: 3547; Downloads: 0
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12.
Interface phenomena between CdTe and ZnTe: Cu back contact
Alessio Bosio, Roberta Ciprian, Alessio Lamperti, I Rago, Barbara Ressel, Greta Rosa, Matija Stupar, E Weschke, 2018, original scientific article

Abstract: Thin film technology has reached a maturity to achieve conversion efficiencies of the order of 22%. Among thin films, CdTe-based photovoltaic modules represent 80% of the total production. Nonetheless, some issues concerning back-contact are still open. In industrial process a chemical etching is required in order to make the CdTe film surface rich in Te. The Te-excess is fundamental in order to form a stable telluride compound with copper and to obtain an ohmic, low-resistance back-contact. Moreover, the Te-excess hinders the fast diffusion of copper in CdTe and its achievement of the junction region, preventing the destruction of the device. In this paper we study a ZnTe:Cu buffer layer deposited onto a CdTe film, characterized by a naturally Te-rich surface obtained with a particular chlorine heat treatment without any chemical etching. Copper diffusion and the CdTe/ZnTe:Cu interface were studied by x-ray
Keywords: solar cells, CdTe, ZnTe:Cu back contact
Published in RUNG: 29.11.2018; Views: 3704; Downloads: 0
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13.
Orbital-dependent electron dynamics in Fe-pnictide superconductors
Ganesh Adhikary, Barbara Ressel, Primož Rebernik Ribič, Jurij Urbančič, Giovanni De Ninno, Damjan Krizmancic, A. Thamizhavel, Kalobaran Maiti, Matija Stupar, 2018, original scientific article

Abstract: We report on orbital-dependent quasiparticle dynamics in EuFe 2 As 2, a parent compound of Fe-based superconductors, and a way to experimentally identify this behavior using time-and angle-resolved photoelectron spectroscopy across the spin density wave transition. We observe two different relaxation timescales for photoexcited d x z/d y z and d x y electrons. While the itinerant d x z/d y z electrons relax faster through the electron-electron scattering channel, d x y electrons form a quasiequilibrium state with the lattice due to their localized character, and the state decays slowly. Our findings suggest that electron correlation in Fe pnictides is an important property, which should carefully be taken into account when describing the electronic properties of both parent and carrier-doped compounds, and therefore establish a strong connection with cuprates
Keywords: photoelectron dynamics, Fe based superconductors
Published in RUNG: 29.11.2018; Views: 3469; Downloads: 0
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Chemical and structural investigation of the cobalt phthalocyanine
Matija Stupar, 2015, master's thesis

Abstract: 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.
Keywords: Cobalt phthalocyanine (CoPc), photoemission spectroscopy (PES), X-ray absorption spectroscopy (XAS), synchrotron radiation, laser, high order harmonic generation (HHG), time resolved spectroscopy
Published in RUNG: 29.09.2015; Views: 8713; Downloads: 280
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