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Vempati S, Deinert JC, Gierster L, Bogner L, Richter C, Mutz N, Blumstengel S, Zykov A, Kowarik S, Garmshausen Y, Hildebrandt J, Hecht S, Stähler J. Uncovering the (un-)occupied electronic structure of a buried hybrid interface. J Phys Condens Matter 2019; 31:094001. [PMID: 30562727 DOI: 10.1088/1361-648x/aaf98a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The energy level alignment at organic/inorganic (o/i) semiconductor interfaces is crucial for any light-emitting or -harvesting functionality. Essential is the access to both occupied and unoccupied electronic states directly at the interface, which is often deeply buried underneath thick organic films and challenging to characterize. We use several complementary experimental techniques to determine the electronic structure of p -quinquephenyl pyridine (5P-Py) adsorbed on ZnO(1 0 -1 0). The parent anchoring group, pyridine, significantly lowers the work function by up to 2.9 eV and causes an occupied in-gap state (IGS) directly below the Fermi level E F. Adsorption of upright-standing 5P-Py also leads to a strong work function reduction of up to 2.1 eV and to a similar IGS. The latter is then used as an initial state for the transient population of three normally unoccupied molecular levels through optical excitation and, due to its localization right at the o/i interface, provides interfacial sensitivity, even for thick 5P-Py films. We observe two final states above the vacuum level and one bound state at around 2 eV above E F, which we attribute to the 5P-Py LUMO. By the separate study of anchoring group and organic dye combined with the exploitation of the occupied IGS for selective interfacial photoexcitation, this work provides a new pathway for characterizing the electronic structure at buried o/i interfaces.
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Affiliation(s)
- S Vempati
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Abt. Physikalische Chemie, Faradayweg 4-6, 14195 Berlin, Germany
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Deinert JC, Wegkamp D, Meyer M, Richter C, Wolf M, Stähler J. Ultrafast exciton formation at the ZnO(1010) surface. Phys Rev Lett 2014; 113:057602. [PMID: 25126937 DOI: 10.1103/physrevlett.113.057602] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2014] [Indexed: 06/03/2023]
Abstract
We study the ultrafast quasiparticle dynamics in and below the ZnO conduction band using femtosecond time-resolved two-photon photoelectron spectroscopy. Above band gap excitation causes hot electron relaxation by electron-phonon scattering down to the Fermi level E_{F} followed by ultrafast (200 fs) formation of a surface exciton (SX). Transient screening of the Coulomb interaction reduces the SX formation probability at high excitation densities near the Mott limit. Located just below the surface, the SX are stable with regard to hydrogen-induced work function modifications and thus the ideal prerequisite for resonant energy transfer applications.
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Affiliation(s)
- J-C Deinert
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Abteilung Physikalische Chemie, Faradayweg 4-6, 14195 Berlin, Germany
| | - D Wegkamp
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Abteilung Physikalische Chemie, Faradayweg 4-6, 14195 Berlin, Germany
| | - M Meyer
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Abteilung Physikalische Chemie, Faradayweg 4-6, 14195 Berlin, Germany
| | - C Richter
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Abteilung Physikalische Chemie, Faradayweg 4-6, 14195 Berlin, Germany
| | - M Wolf
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Abteilung Physikalische Chemie, Faradayweg 4-6, 14195 Berlin, Germany
| | - J Stähler
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Abteilung Physikalische Chemie, Faradayweg 4-6, 14195 Berlin, Germany
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Mitrano M, Cotugno G, Clark SR, Singla R, Kaiser S, Stähler J, Beyer R, Dressel M, Baldassarre L, Nicoletti D, Perucchi A, Hasegawa T, Okamoto H, Jaksch D, Cavalleri A. Pressure-dependent relaxation in the photoexcited mott insulator ET-F2TCNQ: influence of hopping and correlations on quasiparticle recombination rates. Phys Rev Lett 2014; 112:117801. [PMID: 24702420 DOI: 10.1103/physrevlett.112.117801] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2013] [Indexed: 06/03/2023]
Abstract
We measure the ultrafast recombination of photoexcited quasiparticles (holon-doublon pairs) in the one dimensional Mott insulator ET-F(2)TCNQ as a function of external pressure, which is used to tune the electronic structure. At each pressure value, we first fit the static optical properties and extract the electronic bandwidth t and the intersite correlation energy V. We then measure the recombination times as a function of pressure, and we correlate them with the corresponding microscopic parameters. We find that the recombination times scale differently than for metals and semiconductors. A fit to our data based on the time-dependent extended Hubbard Hamiltonian suggests that the competition between local recombination and delocalization of the Mott-Hubbard exciton dictates the efficiency of the recombination.
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Affiliation(s)
- M Mitrano
- Max Planck Institute for the Structure and Dynamics of Matter, Luruper Chaussee 149, 22761 Hamburg, Germany
| | - G Cotugno
- Max Planck Institute for the Structure and Dynamics of Matter, Luruper Chaussee 149, 22761 Hamburg, Germany and Department of Physics, Oxford University, Clarendon Laboratory, Parks Road, OX1 3PU Oxford, United Kingdom
| | - S R Clark
- Department of Physics, Oxford University, Clarendon Laboratory, Parks Road, OX1 3PU Oxford, United Kingdom and Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543, Singapore
| | - R Singla
- Max Planck Institute for the Structure and Dynamics of Matter, Luruper Chaussee 149, 22761 Hamburg, Germany
| | - S Kaiser
- Max Planck Institute for the Structure and Dynamics of Matter, Luruper Chaussee 149, 22761 Hamburg, Germany
| | - J Stähler
- Fritz Haber Institute of the Max Planck Society, Faradayweg 4-6, 14195 Berlin, Germany
| | - R Beyer
- 1. Physikalisches Insitut, Universität Stuttgart, Pfaffenwaldring 57, 70550 Stuttgart, Germany
| | - M Dressel
- 1. Physikalisches Insitut, Universität Stuttgart, Pfaffenwaldring 57, 70550 Stuttgart, Germany
| | - L Baldassarre
- Center for Life NanoScience@Sapienza, Istituto Italiano di Tecnologia, V.le Regina Elena 291, 00185 Rome, Italy
| | - D Nicoletti
- Max Planck Institute for the Structure and Dynamics of Matter, Luruper Chaussee 149, 22761 Hamburg, Germany
| | - A Perucchi
- INSTM UdR Trieste-ST and Elettra - Sincrotrone Trieste S.C.p.A., S.S. 14 km 163.5 in Area Science Park, 34012 Basovizza, Trieste Italy
| | - T Hasegawa
- National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8562, Japan
| | - H Okamoto
- Department of Advanced Material Science, University of Tokyo, Chiba 277-8561, Japan
| | - D Jaksch
- Department of Physics, Oxford University, Clarendon Laboratory, Parks Road, OX1 3PU Oxford, United Kingdom and Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543, Singapore
| | - A Cavalleri
- Max Planck Institute for the Structure and Dynamics of Matter, Luruper Chaussee 149, 22761 Hamburg, Germany and Department of Physics, Oxford University, Clarendon Laboratory, Parks Road, OX1 3PU Oxford, United Kingdom
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Wall S, Wegkamp D, Foglia L, Appavoo K, Nag J, Haglund RF, Stähler J, Wolf M. Ultrafast changes in lattice symmetry probed by coherent phonons. Nat Commun 2012; 3:721. [PMID: 22395612 DOI: 10.1038/ncomms1719] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2011] [Accepted: 02/01/2012] [Indexed: 11/09/2022] Open
Abstract
The electronic and structural properties of a material are strongly determined by its symmetry. Changing the symmetry via a photoinduced phase transition offers new ways to manipulate material properties on ultrafast timescales. However, to identify when and how fast these phase transitions occur, methods that can probe the symmetry change in the time domain are required. Here we show that a time-dependent change in the coherent phonon spectrum can probe a change in symmetry of the lattice potential, thus providing an all-optical probe of structural transitions. We examine the photoinduced structural phase transition in VO(2) and show that, above the phase transition threshold, photoexcitation completely changes the lattice potential on an ultrafast timescale. The loss of the equilibrium-phase phonon modes occurs promptly, indicating a non-thermal pathway for the photoinduced phase transition, where a strong perturbation to the lattice potential changes its symmetry before ionic rearrangement has occurred.
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Affiliation(s)
- S Wall
- Department of Physical Chemistry, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, Berlin 14195, Germany.
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Stähler J, Mehlhorn M, Bovensiepen U, Meyer M, Kusmierek DO, Morgenstern K, Wolf M. Impact of ice structure on ultrafast electron dynamics in D2O clusters on Cu(111). Phys Rev Lett 2007; 98:206105. [PMID: 17677714 DOI: 10.1103/physrevlett.98.206105] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2006] [Indexed: 05/16/2023]
Abstract
The structure of D2O clusters on a Cu(111) surface and the femtosecond dynamics of photoexcited excess electrons are investigated by low-temperature scanning tunneling microscopy and two-photon photoemission spectroscopy. Two types of amorphous ice clusters, porous and compact, which exhibit characteristic differences in electron dynamics, are identified. By titration with Xe we show that in both structures solvated electrons preferentially bind on the cluster surface.
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Affiliation(s)
- J Stähler
- Freie Universität Berlin, Fachbereich Physik, Arnimallee 14, 14195 Berlin-Dahlem, Germany
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Oppelt P, Plathow D, Oppelt A, Stähler J, Petrich S, Scharl A, Costa S, Jesgarz J, Kaufmann M, Bergh B. [Feather--data acquisition in gynaecology and obstetrics]. Zentralbl Gynakol 2002; 124:362-7. [PMID: 12439763 DOI: 10.1055/s-2002-35535] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Nowadays many types of medical documentation are based on computer facilities. Unfortunately, this involves the considerable disadvantage that almost every single department and specialty has its own software programs, with the physician having to learn a whole range of different programs. In addition, data sometimes have to be entered twice - since although open interfaces are often available, the elaborate programming required to transfer data from outside programs makes the financial costs too high. Since 1995 the University's of Frankfurt am Main Department of Gynecology and Obstetrics has therefore developed a consistent program of its own under Windows NT for in-patient facilities, as well as for some outpatient services. The program does not aim to achieve everything that is technically possible, but focuses primarily on user requirements. In addition to the general requirements for medical documentation in gynecology and obstetrics, the program can also handle perinatal inquiries and gynecological quality control (QSmed [Qualitätssicherung in der Medizin] of the BQS [Bundesgeschäftsstelle Qualitätssicherung]).
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Affiliation(s)
- P Oppelt
- Universitäts-Frauenklinik, Universitätsstrasse 21-23, 91054 Erlangen, Germany.
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Müller-Wittig WK, Bisler A, Bockholt U, Los Arcos JL, Oppelt P, Stähler J, Voss G. LAHYSTOTRAIN development and evaluation of a complex training system for hysteroscopy. Stud Health Technol Inform 2001; 81:336-40. [PMID: 11317765] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/19/2023]
Abstract
Hysteroscopy has already become an irreplaceable method in gynaecoloic diagnosis and therapy. In the diagnostic case the hysteroscope with a 30 degrees optic is insert transvaginally, in the therapeutic case the resectoscope with a 12 degrees optic is used. The endoscopic intervention requires special surgical skills for endoscope handling and remote instrument control. To acquire these skills currently hands-on training in clinical praxis has become standard, which is linked with higher danger for the women. To overcome current drawbacks of traditional training methods the European project LAHYSTOTRAIN was set up, that tries to combine Virtual Reality (VR), Multimedia (MM) technology, and Intelligent Tutoring Systems (ITS) to develop an alternative training system for hysteroscopic interventions. The first prototype of the LAHYSTOTRAIN demonstrator has been shown on several European conferences. An evaluation of the system was performed, with the idea, to collect feedback and impressions, that should be considered in further developments. This paper presents the LAHYSTOTRAIN prototype and the results of these evaluations.
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Affiliation(s)
- W K Müller-Wittig
- Fraunhofer-Institut für Graphische Datenverarbeitung (Fraunhofer-IGD), Department Visualization & Virtual Reality, Rundeturmstrasse 6, D-64283 Darmstadt, Germany.
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Voss G, Bockholt U, Los Arcos JL, Müller W, Oppelt P, Stähler J. LAHYSTOTRAIN intelligent training system for laparoscopy and hysteroscopy. Stud Health Technol Inform 2000; 70:359-64. [PMID: 10977572] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
Abstract
Rapid developments in the medical field, as an expanding knowledge base and emerging new technologies require continuing medical education to achieve life long learning and to keep the surgeons up to date. Consequently, specific training is necessary to guarantee qualification of the surgeons. The goal of LAHYSTOTRAIN is to overcome the current drawbacks of traditional training methods for laparoscopic/hysteroscopic procedures. A computer-assisted simulator for training and quality control in laparoscopy and hysteroscopy is developed using Virtual Reality (VR), Multimedia (MM) technology, and Intelligent Tutoring Systems (ITS).
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Affiliation(s)
- G Voss
- Fraunhofer-Institut für Graphische Datenverarbeitung (Fraunhofer-IGD), Department Visualization & Virtual Reality, Darmstadt, Germany.
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Oppelt P, Stähler J, Miller W, Kaufmann M. Lahystotrain - integration of virtual environments and intelligent training systems for laparoscopy and hysteroscopy. Int J Gynaecol Obstet 2000. [DOI: 10.1016/s0020-7292(00)82478-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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