@article{JohanssonLeitnerBidermaneetal.2022, author = {Johansson, Fredrik O. L. and Leitner, Torsten and Bidermane, Ieva and Born, Artur and F{\"o}hlisch, Alexander and Svensson, Svante and M{\aa}rtensson, Nils and Lindblad, Andreas}, title = {Auger- and photoelectron coincidences of molecular O2 adsorbed on Ag(111)}, series = {Journal of electron spectroscopy and related phenomena : the international journal on theoretical and experimental aspects of electron spectroscopy}, volume = {256}, journal = {Journal of electron spectroscopy and related phenomena : the international journal on theoretical and experimental aspects of electron spectroscopy}, publisher = {Elsevier}, address = {New York, NY [u.a.]}, issn = {0368-2048}, doi = {10.1016/j.elspec.2022.147174}, pages = {6}, year = {2022}, abstract = {The oxygen on Ag(111) system has been investigated with Auger electron-photoelectron coincidence spectroscopy (APECS). The coincidence spectra between O 1s core level photoelectrons and O KLL Auger electrons have been studied together with Ag(3)d/AgM4,5NN coincidences. We also describe the electron-electron coincidence spectrometer setup, CoESCA, consisting of two angle resolved time-of-flight spectrometers at a synchrotron light source. Contributions from molecular oxygen and chemisorbed oxygen are assigned using the coincidence data, conclusions are drawn primarily from the O 1s/O KLL data. The data acquisition and treatment procedure are also outlined. The chemisorbed oxygen species observed are relevant for the catalytic ethylene oxidation.}, language = {en} } @article{SorgenfreiGiangrisostomiJayetal.2021, author = {Sorgenfrei, Nomi and Giangrisostomi, Erika and Jay, Raphael Martin and K{\"u}hn, Danilo and Neppl, Stefan and Ovsyannikov, Ruslan and Sezen, Hikmet and Svensson, Svante and F{\"o}hlisch, Alexander}, title = {Photodriven transient picosecond top-layer semiconductor to metal phase-transition in p-doped molybdenum disulfide}, series = {Advanced materials}, volume = {33}, journal = {Advanced materials}, number = {14}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {0935-9648}, doi = {10.1002/adma.202006957}, pages = {8}, year = {2021}, abstract = {Visible light is shown to create a transient metallic S-Mo-S surface layer on bulk semiconducting p-doped indirect-bandgap 2H-MoS2. Optically created electron-hole pairs separate in the surface band bending region of the p-doped semiconducting crystal causing a transient accumulation of electrons in the surface region. This triggers a reversible 2H-semiconductor to 1T-metal phase-transition of the surface layer. Electron-phonon coupling of the indirect-bandgap p-doped 2H-MoS2 enables this efficient pathway even at a low density of excited electrons with a distinct optical excitation threshold and saturation behavior. This mechanism needs to be taken into consideration when describing the surface properties of illuminated p-doped 2H-MoS2. In particular, light-induced increased charge mobility and surface activation can cause and enhance the photocatalytic and photoassisted electrochemical hydrogen evolution reaction of water on 2H-MoS2. Generally, it opens up for a way to control not only the surface of p-doped 2H-MoS2 but also related dichalcogenides and layered systems. The findings are based on the sensitivity of time-resolved electron spectroscopy for chemical analysis with photon-energy-tuneable synchrotron radiation.}, language = {en} } @article{MartenssonFoehlischSvensson2022, author = {Martensson, Nils and F{\"o}hlisch, Alexander and Svensson, Svante}, title = {Uppsala and Berkeley}, series = {Journal of vacuum science \& technology : JVST ; an AVS journal / A}, volume = {40}, journal = {Journal of vacuum science \& technology : JVST ; an AVS journal / A}, number = {4}, publisher = {American Institute of Physics}, address = {New York}, issn = {0734-2101}, doi = {10.1116/6.0001879}, pages = {11}, year = {2022}, abstract = {The development of modern photoelectron spectroscopy is reviewed with a special focus on the importance of research at Uppsala University and at Berkeley. The influence of two pioneers, Kai Siegbahn and Dave Shirley, is underlined. Early interaction between the two centers helped to kick-start the field. Both laboratories have continued to play an important role in the field, both in terms of creating new experimental capabilities and developing the theoretical understanding of the spectroscopic processes.}, language = {en} } @article{GiangrisostomiOvsyannikovSorgenfreietal.2018, author = {Giangrisostomi, Erika and Ovsyannikov, Ruslan and Sorgenfrei, Florian and Zhang, Teng and Lindblad, Andreas and Sassa, Yasmine and Cappel, Ute B. and Leitner, Torsten and Mitzner, Rolf and Svensson, Svante and Martensson, Nils and F{\"o}hlisch, Alexander}, title = {Low Dose Photoelectron Spectroscopy at BESSY II}, series = {Journal of electron spectroscopy and related phenomena : the international journal on theoretical and experimental aspects of electron spectroscopy}, volume = {224}, journal = {Journal of electron spectroscopy and related phenomena : the international journal on theoretical and experimental aspects of electron spectroscopy}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0368-2048}, doi = {10.1016/j.elspec.2017.05.011}, pages = {68 -- 78}, year = {2018}, abstract = {The implementation of a high-transmission, angular-resolved time-of-Right electron spectrometer with a 1.25 MHz pulse selector at the PM4 soft X-ray dipole beamline of the synchrotron BESSY II creates unique capabilities to inquire electronic structure via photoelectron spectroscopy with a minimum of radiation dose. Solid-state samples can be prepared and characterized with standard UHV techniques and rapidly transferred from various preparation chambers to a 4-axis temperature-controlled measurement stage. A synchronized MHz laser system enables excited-state characterization and dynamical studies starting from the picosecond timescale. This article introduces the principal characteristics of the PM4 beamline and LowDosePES end-station. Recent results from graphene, an organic hole transport material for solar cells and the transition metal dichalcogenide MoS2 are presented to demonstrate the instrument performances.}, language = {en} } @article{KuehnSorgenfreiGiangrisostomietal.2018, author = {K{\"u}hn, Danilo and Sorgenfrei, Florian and Giangrisostomi, Erika and Jay, Raphael and Musazay, Abdurrahman and Ovsyannikov, Ruslan and Strahlman, Christian and Svensson, Svante and M{\aa}rtensson, Nils and F{\"o}hlisch, Alexander}, title = {Capabilities of angle resolved time of flight electron spectroscopy with the 60 degrees wide angle acceptance lens}, series = {Journal of electron spectroscopy and related phenomena : the international journal on theoretical and experimental aspects of electron spectroscopy}, volume = {224}, journal = {Journal of electron spectroscopy and related phenomena : the international journal on theoretical and experimental aspects of electron spectroscopy}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0368-2048}, doi = {10.1016/j.elspec.2017.06.008}, pages = {45 -- 50}, year = {2018}, abstract = {The simultaneous detection of energy, momentum and temporal information in electron spectroscopy is the key aspect to enhance the detection efficiency in order to broaden the range of scientific applications. Employing a novel 60 degrees wide angle acceptance lens system, based on an additional accelerating electron optical element, leads to a significant enhancement in transmission over the previously employed 30 degrees electron lenses. Due to the performance gain, optimized capabilities for time resolved electron spectroscopy and other high transmission applications with pulsed ionizing radiation have been obtained. The energy resolution and transmission have been determined experimentally utilizing BESSY II as a photon source. Four different and complementary lens modes have been characterized. (C) 2017 The Authors. Published by Elsevier B.V.}, language = {en} } @article{CappelSvanstromLanzilottoetal.2017, author = {Cappel, Ute B. and Svanstrom, Sebastian and Lanzilotto, Valeria and Johansson, Fredrik O. L. and Aitola, Kerttu and Philippe, Bertrand and Giangrisostomi, Erika and Ovsyannikov, Ruslan and Leitner, Torsten and F{\"o}hlisch, Alexander and Svensson, Svante and Martensson, Nils and Boschloo, Gerrit and Lindblad, Andreas and Rensmo, Hakan}, title = {Partially Reversible Photoinduced Chemical Changes in a Mixed-Ion Perovskite Material for Solar Cells}, series = {ACS applied materials \& interfaces}, volume = {9}, journal = {ACS applied materials \& interfaces}, publisher = {American Chemical Society}, address = {Washington}, issn = {1944-8244}, doi = {10.1021/acsami.7b10643}, pages = {34970 -- 34978}, year = {2017}, abstract = {Metal halide perovskites have emerged as materials of high interest for solar energy-to-electricity conversion, and in particular, the use of mixed-ion structures has led to high power conversion efficiencies and improved stability. For this reason, it is important to develop means to obtain atomic level understanding of the photoinduced behavior of these materials including processes such as photoinduced phase separation and ion migration. In this paper, we implement a new methodology combining visible laser illumination of a mixed-ion perovskite ((FAP-bI(3))(0.85)(MAPbBr(3))(0.15)) with the element specificity and chemical sensitivity of core-level photoelectron spectroscopy. By carrying out measurements at a synchrotron beamline optimized for low X-ray fluxes, we are able to avoid sample changes due to X-ray illumination and are therefore able to monitor what sample changes are induced by visible illumination only. We find that laser illumination causes partially reversible chemistry in the surface region, including enrichment of bromide at the surface, which could be related to a phase separation into bromide- and iodide-rich phases. We also observe a partially reversible formation of metallic lead in the perovskite structure. These processes occur on the time scale of minutes during illumination. The presented methodology has a large potential for understanding light-induced chemistry in photoactive materials and could specifically be extended to systematically study the impact of morphology and composition on the photostability of metal halide perovskites.}, language = {en} } @misc{KuehnSorgenfreiGiangrisostomietal.2018, author = {K{\"u}hn, Danilo and Sorgenfrei, Florian and Giangrisostomi, Erika and Jay, Raphael Martin and Musazayb, Abdurrahman and Ovsyannikov, Ruslan and Str{\aa}hlman, Christian and Svensson, Svante and M{\aa}rtensson, Nils and F{\"o}hlisch, Alexander}, title = {Capabilities of angle resolved time of flight electron spectroscopy with the 60 degrees wide angle acceptance lens}, series = {Postprints der Universit{\"a}t Potsdam Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam Mathematisch-Naturwissenschaftliche Reihe}, number = {782}, issn = {1866-8372}, doi = {10.25932/publishup-43662}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-436629}, pages = {45 -- 50}, year = {2018}, abstract = {The simultaneous detection of energy, momentum and temporal information in electron spectroscopy is the key aspect to enhance the detection efficiency in order to broaden the range of scientific applications. Employing a novel 60 degrees wide angle acceptance lens system, based on an additional accelerating electron optical element, leads to a significant enhancement in transmission over the previously employed 30 degrees electron lenses. Due to the performance gain, optimized capabilities for time resolved electron spectroscopy and other high transmission applications with pulsed ionizing radiation have been obtained. The energy resolution and transmission have been determined experimentally utilizing BESSY II as a photon source. Four different and complementary lens modes have been characterized. (C) 2017 The Authors. Published by Elsevier B.V.}, language = {en} }