Stabilisierung von Hochspinzuständen in übergangsmetalldotierten Siliziumclustern
Zusammenfassung der Projektergebnisse
The aim of this project was to tailor the electronic and optical properties of silicon clusters by combining doping and surface modification. The ultimate goal was to arrive at a level of understanding where targeted control of these properties would become feasible. This required a fundamental investigation of doped silicon clusters and their interaction with adsorbate molecules, as well as surface passivation. A major effort was to establish an understanding of the electronic properties in the exohedral and endohedral size ranges of transition-metal doped silicon clusters, which seemed to be characterized by localized and delocalized valence electrons of the impurity atom, respectively, leading to distinct electronic, geometric, and magnetic properties in both size regimes. This insight was to be used for recovery of high spin states in the endohedral size regime by hydrogen passivation of the silicon shell. Most of the original goals have been reached. We could establish the general transition from high-spin states, for exohedral structures with localized valence electrons at the low-coordinated transition-metal dopant, to low spin states for endohedral structures with delocalized valence electrons and highcoordinated transition metal atom. This was achieved by x-ray absorption and x-ray magnetic circular dichroism spectroscopy of size-selected transition-metal-doped silicon cluster ions in our unique cryogenic ion trap setup. We could also demonstrate that hydrogen passivation indeed restores highspin states for clusters in a size range where bare clusters are endohedral and low spin. This recovery is the result of geometrical rearrangements in the hydrogen passivated clusters that leads to amorphous, exohedral structures with localized 3d valence electrons. Insight into these phenomena was also gained by comparison to additional results from well-characterized transition-metal-benzene complexes that, although not part of the original proposal, turned out to be very useful model systems for x-ray absorption and x-ray circular dichroism spectroscopy.
Projektbezogene Publikationen (Auswahl)
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Communication: Highest occupied molecular orbital – lowest unoccupied molecular orbital gaps of doped silicon clusters from core level spectroscopy, J. Chem. Phys. 134, 041102, 2011
J.T. Lau, M. Vogel, A. Langenberg, K. Hirsch, J. Rittmann, V. Zamudio-Bayer, T. Möller, B. von Issendorff
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Electronic properties of transition metal doped silicon clusters, Doctoral thesis, Technische Universität Berlin, 2011
J. Rittmann
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2p core-level binding energies of size-selected free silicon clusters: Chemical shifts and cluster structure, Phys. Rev. B 85, 195454, 2012
M. Vogel, K. Hirsch, A. Langenberg, J. Rittmann, V. Zamudio-Bayer, A. Kulesza, R. Mitric, T. Möller, B. v. Issendorff, J.T. Lau
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Coordination-driven magnetic-to-nonmagnetic transition in manganese doped silicon clusters, Phys. Rev. B 88, 115425, 2013
V. Zamudio-Bayer, L. Leppert, K. Hirsch, A. Langenberg, J. Rittmann, M. Kossick, M. Vogel, R. Richter, A. Terasaki, T. Möller, B. v. Issendorff, S. Kümmel, J.T. Lau
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Electronic and magnetic properties of impurities embedded in non-magnetic finite hosts, Doctoral thesis, Technische Universität Berlin, 2013
K. Hirsch
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Magnetic properties of pure and mixed 3d5 transition metal clusters, Doctoral thesis, Technische Universität Berlin, 2014
V. Zamudio-Bayer
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Higher ionization energies from sequential vacuum-ultraviolet multiphoton ionization of size-selected silicon cluster cations, J. Phys. Chem. C 119, 11148, 2015
C. Kasigkeit, K. Hirsch, A. Langenberg, T. Möller, J. Probst, J. Rittmann, M. Vogel, J. Wittich, V. Zamudio- Bayer, B. von Issendorff, J.T. Lau
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Impurity electron localization in early-transition-metal-doped gold clusters, J. Phys. Chem. C 119, 11184, 2015
K. Hirsch, V. Zamudio-Bayer, A. Langenberg, M. Vogel, J. Rittmann, S. Forin, T. Möller, B. von Issendorff, and J.T. Lau
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Magnetic moments of chromium-doped gold clusters: The Anderson impurity model in finite systems, Phys. Rev. Lett. 114, 087202, 2015
K. Hirsch, V. Zamudio-Bayer, A. Langenberg, M. Niemeyer, B. Langbehn, T. Möller, A. Terasaki, B. v. Issendorff, J.T. Lau
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Probing the electronic structure and magnetic properties of size-selected free atomic, molecular, and cluster ions with x-ray spectroscopy – an ion trap approach, Habilitation thesis, Technische Universität Berlin, 2015
J.T. Lau
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Size-dependent ligand quenching of ferromagnetism in Co3(benzene)n+ clusters studied with XMCD spectroscopy, J. Phys. Chem. Lett. 7, 4568, 2016
S. T. Akin, V. Zamudio-Bayer, K. Duanmu, G. Leistner, K Hirsch, C. Bülow, A. Ławicki, A. Terasaki, B. von Issendorff, D. G. Truhlar, J.T. Lau, M.A. Duncan
