2023
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| 7. | A. Windischbacher Investigating Ground and Excited State Properties of Complex Organic/Inorganic Interfaces With Ab-Initio Calculations PhD Thesis 2023. @phdthesis{nokey,
title = {Investigating Ground and Excited State Properties of Complex Organic/Inorganic Interfaces With Ab-Initio Calculations},
author = {A. Windischbacher},
year = {2023},
date = {2023-10-02},
keywords = {},
pubstate = {published},
tppubtype = {phdthesis}
}
|
| 6. | C. S. Kern, A. Windischbacher, P. Puschnig Photoemission orbital tomography for excitons in organic molecules Journal Article In: Phys. Rev. B, vol. 108, pp. 085132, 2023. @article{Kern2023,
title = {Photoemission orbital tomography for excitons in organic molecules},
author = {C. S. Kern and A. Windischbacher and P. Puschnig},
doi = {10.1103/PhysRevB.108.085132},
year = {2023},
date = {2023-08-22},
urldate = {2023-08-22},
journal = {Phys. Rev. B},
volume = {108},
pages = {085132},
abstract = {Driven by recent developments in time-resolved photoemission spectroscopy, we extend the successful method of photoemission orbital tomography (POT) to excitons. Our theory retains the intuitive orbital picture of POT, while respecting both the entangled character of the exciton wave function and the energy conservation in the photoemission process. Analyzing results from three organic molecules, we classify generic exciton structures and give a simple interpretation in terms of natural transition orbitals. We validate our findings by directly simulating pump-probe experiments with time-dependent density functional theory.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Driven by recent developments in time-resolved photoemission spectroscopy, we extend the successful method of photoemission orbital tomography (POT) to excitons. Our theory retains the intuitive orbital picture of POT, while respecting both the entangled character of the exciton wave function and the energy conservation in the photoemission process. Analyzing results from three organic molecules, we classify generic exciton structures and give a simple interpretation in terms of natural transition orbitals. We validate our findings by directly simulating pump-probe experiments with time-dependent density functional theory. |
2022
|
| 5. | M. Stredansky, S. Moro, M. Corva, H. M. Sturmeit, V. Mischke, D. Janas, I. Cojocariu, M. Jugovac, A. Cossaro, A. Verdini, L. Floreano, Z. Feng, A. Sala, G. Comelli, A. Windischbacher, P. Puschnig, C. Hohner, M. Kettner, J. Libuda, M. Cinchetti, C. M. Schneider, V. Feyer, E. Vesselli, G. Zamborlini Disproportionation of Nitric Oxide at a Surface-Bound Nickel Porphyrinoid Journal Article In: Angew. Chem. Int. Ed., vol. 61, pp. e202201916, 2022. @article{Stredansky2022,
title = {Disproportionation of Nitric Oxide at a Surface-Bound Nickel Porphyrinoid},
author = {M. Stredansky and S. Moro and M. Corva and H. M. Sturmeit and V. Mischke and D. Janas and I. Cojocariu and M. Jugovac and A. Cossaro and A. Verdini and L. Floreano and Z. Feng and A. Sala and G. Comelli and A. Windischbacher and P. Puschnig and C. Hohner and M. Kettner and J. Libuda and M. Cinchetti and C. M. Schneider and V. Feyer and E. Vesselli and G. Zamborlini},
doi = {10.1002/anie.202201916},
year = {2022},
date = {2022-01-01},
journal = {Angew. Chem. Int. Ed.},
volume = {61},
pages = {e202201916},
abstract = {Uncommon metal oxidation states in porphyrinoid cofactors are responsible for the activity of many enzymes. The F430 and P450nor co-factors, with their reduced NiI- and FeIII-containing tetrapyrrolic cores, are prototypical examples of biological systems involved in methane formation and in the reduction of nitric oxide, respectively. Herein, using a comprehensive range of experimental and theoretical methods, we raise evidence that nickel tetraphenyl porphyrins deposited in vacuo on a copper surface are reactive towards nitric oxide disproportionation at room temperature. The interpretation of the measurements is far from being straightforward due to the high reactivity of the different nitrogen oxides species (eventually present in the residual gas background) and of the possible reaction intermediates. The picture is detailed in order to disentangle the challenging complexity of the system, where even a small fraction of contamination can change the scenario.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Uncommon metal oxidation states in porphyrinoid cofactors are responsible for the activity of many enzymes. The F430 and P450nor co-factors, with their reduced NiI- and FeIII-containing tetrapyrrolic cores, are prototypical examples of biological systems involved in methane formation and in the reduction of nitric oxide, respectively. Herein, using a comprehensive range of experimental and theoretical methods, we raise evidence that nickel tetraphenyl porphyrins deposited in vacuo on a copper surface are reactive towards nitric oxide disproportionation at room temperature. The interpretation of the measurements is far from being straightforward due to the high reactivity of the different nitrogen oxides species (eventually present in the residual gas background) and of the possible reaction intermediates. The picture is detailed in order to disentangle the challenging complexity of the system, where even a small fraction of contamination can change the scenario. |
| 4. | M. S. Sättele, A. Windischbacher, K. Greulich, L. Egger, A. Haags, H. Kirschner, R. Ovsyannikov, E. Giangrisostomi, A. Gottwald, M. Richter, S. Soubatch, F. S. Tautz, M. G. Ramsey, P. Puschnig, G. Koller, H. F. Bettinger, T. Chassé, H. Peisert Hexacene on Cu(110) and Ag(110): Influence of the Substrate on Molecular Orientation and Interfacial Charge Transfer Journal Article In: J. Phys. Chem. C, vol. 126, pp. 5036-5045, 2022. @article{Saettele2022,
title = {Hexacene on Cu(110) and Ag(110): Influence of the Substrate on Molecular Orientation and Interfacial Charge Transfer},
author = {M. S. Sättele and A. Windischbacher and K. Greulich and L. Egger and A. Haags and H. Kirschner and R. Ovsyannikov and E. Giangrisostomi and A. Gottwald and M. Richter and S. Soubatch and F. S. Tautz and M. G. Ramsey and P. Puschnig and G. Koller and H. F. Bettinger and T. Chassé and H. Peisert},
doi = {10.1021/acs.jpcc.2c00081},
year = {2022},
date = {2022-01-01},
journal = {J. Phys. Chem. C},
volume = {126},
pages = {5036-5045},
abstract = {Hexacene, composed of six linearly fused benzene rings, is an organic semiconductor material with superior electronic properties. The fundamental understanding of the electronic and chemical properties is prerequisite to any possible application in devices. We investigate the orientation and interface properties of highly ordered hexacene monolayers on Ag(110) and Cu(110) with X-ray photoemission spectroscopy (XPS), photoemission orbital tomography (POT), X-ray absorption spectroscopy (XAS), low-energy electron diffraction (LEED), scanning tunneling microscopy (STM), and density functional theory (DFT). We find pronounced differences in the structural arrangement of the molecules and the electronic properties at the metal/organic interfaces for the two substrates. While on Cu(110) the molecules adsorb with their long molecular axis parallel to the high symmetry substrate direction, on Ag(110), hexacene adsorbs in an azimuthally slightly rotated geometry with respect to the metal rows of the substrate. In both cases, molecular planes are oriented parallel to the substrate. A pronounced charge transfer from both substrates to different molecular states affects the effective charge of different C atoms of the molecule. Through analysis of experimental and theoretical data, we found out that on Ag(110) the LUMO of the molecule is occupied through charge transfer from the metal, whereas on Cu(110) even the LUMO+1 receives a charge. Interface dipoles are determined to a large extent by the push-back effect, which are also found to differ significantly between 6A/Ag(110) and 6A/Cu(110).},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Hexacene, composed of six linearly fused benzene rings, is an organic semiconductor material with superior electronic properties. The fundamental understanding of the electronic and chemical properties is prerequisite to any possible application in devices. We investigate the orientation and interface properties of highly ordered hexacene monolayers on Ag(110) and Cu(110) with X-ray photoemission spectroscopy (XPS), photoemission orbital tomography (POT), X-ray absorption spectroscopy (XAS), low-energy electron diffraction (LEED), scanning tunneling microscopy (STM), and density functional theory (DFT). We find pronounced differences in the structural arrangement of the molecules and the electronic properties at the metal/organic interfaces for the two substrates. While on Cu(110) the molecules adsorb with their long molecular axis parallel to the high symmetry substrate direction, on Ag(110), hexacene adsorbs in an azimuthally slightly rotated geometry with respect to the metal rows of the substrate. In both cases, molecular planes are oriented parallel to the substrate. A pronounced charge transfer from both substrates to different molecular states affects the effective charge of different C atoms of the molecule. Through analysis of experimental and theoretical data, we found out that on Ag(110) the LUMO of the molecule is occupied through charge transfer from the metal, whereas on Cu(110) even the LUMO+1 receives a charge. Interface dipoles are determined to a large extent by the push-back effect, which are also found to differ significantly between 6A/Ag(110) and 6A/Cu(110). |
2021
|
| 3. | H. M. Sturmeit, I. Cojocariu, A. Windischbacher, P. Puschnig, C. Piamonteze, M. Jugovac, A. Sala, C. Africh, G. Comelli, A. Cossaro, A. Verdini, L. Floreano, M. Stredansky, E. Vesselli, C. Hohner, M. Kettner, J. Libuda, C. M. Schneider, G. Zamborlini, M. Cinchetti, V. Feyer Room-temperature on-spin-switching and tuning in a porphyrin-based multifunctional interface Journal Article In: Small, vol. 17, pp. 2104779, 2021. @article{Sturmeit2021,
title = {Room-temperature on-spin-switching and tuning in a porphyrin-based multifunctional interface},
author = {H. M. Sturmeit and I. Cojocariu and A. Windischbacher and P. Puschnig and C. Piamonteze and M. Jugovac and A. Sala and C. Africh and G. Comelli and A. Cossaro and A. Verdini and L. Floreano and M. Stredansky and E. Vesselli and C. Hohner and M. Kettner and J. Libuda and C. M. Schneider and G. Zamborlini and M. Cinchetti and V. Feyer},
doi = {10.1002/smll.202104779},
year = {2021},
date = {2021-01-01},
journal = {Small},
volume = {17},
pages = {2104779},
abstract = {Molecular interfaces formed between metals and molecular compounds offer a great potential as building blocks for future opto-electronics and spintronics devices. Here, a combined theoretical and experimental spectro-microscopy approach is used to show that the charge transfer occurring at the interface between nickel tetraphenyl porphyrins and copper changes both spin and oxidation states of the Ni ion from [Ni(II)},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Molecular interfaces formed between metals and molecular compounds offer a great potential as building blocks for future opto-electronics and spintronics devices. Here, a combined theoretical and experimental spectro-microscopy approach is used to show that the charge transfer occurring at the interface between nickel tetraphenyl porphyrins and copper changes both spin and oxidation states of the Ni ion from [Ni(II) |
| 2. | T. G. Boné, A. Windischbacher, M. S. Sättele, K. Greulich, L. Egger, T. Jauk, F. Lackner, H. F. Bettinger, H. Peisert, T. Chassé, M. G. Ramsey, M. Sterrer, G. Koller, P. Puschnig Demonstrating the Impact of the Adsorbate Orientation on the Charge Transfer at Organic-Metal Interfaces Journal Article In: J. Phys. Chem. C, vol. 125, pp. 9129-9137, 2021. @article{Bone2021,
title = {Demonstrating the Impact of the Adsorbate Orientation on the Charge Transfer at Organic-Metal Interfaces},
author = {T. G. Boné and A. Windischbacher and M. S. Sättele and K. Greulich and L. Egger and T. Jauk and F. Lackner and H. F. Bettinger and H. Peisert and T. Chassé and M. G. Ramsey and M. Sterrer and G. Koller and P. Puschnig},
doi = {10.1021/acs.jpcc.1c01306},
year = {2021},
date = {2021-01-01},
journal = {J. Phys. Chem. C},
volume = {125},
pages = {9129-9137},
abstract = {Charge-transfer processes at molecule–metal interfaces play a key role in tuning the charge injection properties in organic-based devices and thus, ultimately, the device performance. Here, the metal’s work function and the adsorbate’s electron affinity are the key factors that govern the electron transfer at the organic/metal interface. In our combined experimental and theoretical work, we demonstrate that the adsorbate’s orientation may also be decisive for the charge transfer. By thermal cycloreversion of diheptacene isomers, we manage to produce highly oriented monolayers of the rodlike, electron-acceptor molecule heptacene on a Cu(110) surface with molecules oriented either along or perpendicular to the close-packed metal rows. This is confirmed by scanning tunneling microscopy (STM) images as well as by angle-resolved ultraviolet photoemission spectroscopy (ARUPS). By utilizing photoemission tomography momentum maps, we show that the lowest unoccupied molecular orbital (LUMO) is fully occupied and also, the LUMO + 1 gets significantly filled when heptacene is oriented along the Cu rows. Conversely, for perpendicularly aligned heptacene, the molecular energy levels are shifted significantly toward the Fermi energy, preventing charge transfer to the LUMO + 1. These findings are fully confirmed by our density functional calculations and demonstrate the possibility to tune the charge transfer and level alignment at organic–metal interfaces through the adjustable molecular alignment.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Charge-transfer processes at molecule–metal interfaces play a key role in tuning the charge injection properties in organic-based devices and thus, ultimately, the device performance. Here, the metal’s work function and the adsorbate’s electron affinity are the key factors that govern the electron transfer at the organic/metal interface. In our combined experimental and theoretical work, we demonstrate that the adsorbate’s orientation may also be decisive for the charge transfer. By thermal cycloreversion of diheptacene isomers, we manage to produce highly oriented monolayers of the rodlike, electron-acceptor molecule heptacene on a Cu(110) surface with molecules oriented either along or perpendicular to the close-packed metal rows. This is confirmed by scanning tunneling microscopy (STM) images as well as by angle-resolved ultraviolet photoemission spectroscopy (ARUPS). By utilizing photoemission tomography momentum maps, we show that the lowest unoccupied molecular orbital (LUMO) is fully occupied and also, the LUMO + 1 gets significantly filled when heptacene is oriented along the Cu rows. Conversely, for perpendicularly aligned heptacene, the molecular energy levels are shifted significantly toward the Fermi energy, preventing charge transfer to the LUMO + 1. These findings are fully confirmed by our density functional calculations and demonstrate the possibility to tune the charge transfer and level alignment at organic–metal interfaces through the adjustable molecular alignment. |
| 1. | M. S. Sättele, A. Windischbacher, L. Egger, A. Haags, P. Hurdax, H. Kirschner, A. Gottwald, M. Richter, F. C. Bocquet, S. Soubatch, F. S. Tautz, H. F. Bettinger, H. Peisert, T. Chassé, M. G. Ramsey, P. Puschnig, G. Koller Going beyond Pentacene: Photoemission Tomography of a Heptacene Monolayer on Ag(110) Journal Article In: J. Phys. Chem. C, vol. 125, pp. 2918-2925, 2021. @article{Saettele2020,
title = {Going beyond Pentacene: Photoemission Tomography of a Heptacene Monolayer on Ag(110)},
author = {M. S. Sättele and A. Windischbacher and L. Egger and A. Haags and P. Hurdax and H. Kirschner and A. Gottwald and M. Richter and F. C. Bocquet and S. Soubatch and F. S. Tautz and H. F. Bettinger and H. Peisert and T. Chassé and M. G. Ramsey and P. Puschnig and G. Koller},
doi = {10.1021/acs.jpcc.0c09062},
year = {2021},
date = {2021-01-01},
journal = {J. Phys. Chem. C},
volume = {125},
pages = {2918-2925},
abstract = {Longer acenes such as heptacene are promising candidates for optoelectronic applications but are unstable in their bulk structure as they tend to dimerize. This makes the growth of well-defined monolayers and films problematic. In this article, we report the successful preparation of a highly oriented monolayer of heptacene on Ag(110) by thermal cycloreversion of diheptacenes. In a combined effort of angle-resolved photoemission spectroscopy and density functional theory (DFT) calculations, we characterize the electronic and structural properties of the molecule on the surface in detail. Our investigations allow us to unambiguously confirm the successful fabrication of a highly oriented complete monolayer of heptacene and to describe its electronic structure. By comparing experimental momentum maps of photoemission from frontier orbitals of heptacene and pentacene, we shed light on differences between these two acenes regarding their molecular orientation and energy-level alignment on the metal surfaces.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Longer acenes such as heptacene are promising candidates for optoelectronic applications but are unstable in their bulk structure as they tend to dimerize. This makes the growth of well-defined monolayers and films problematic. In this article, we report the successful preparation of a highly oriented monolayer of heptacene on Ag(110) by thermal cycloreversion of diheptacenes. In a combined effort of angle-resolved photoemission spectroscopy and density functional theory (DFT) calculations, we characterize the electronic and structural properties of the molecule on the surface in detail. Our investigations allow us to unambiguously confirm the successful fabrication of a highly oriented complete monolayer of heptacene and to describe its electronic structure. By comparing experimental momentum maps of photoemission from frontier orbitals of heptacene and pentacene, we shed light on differences between these two acenes regarding their molecular orientation and energy-level alignment on the metal surfaces. |
