kMap.py: A Python program for simulation and data analysis in photoemission tomography

Brandstetter, Dominik; Yang, Xiaosheng; Lüftner, Diana; Tautz, F. Stefan; Puschnig, Peter

doi:10.1016/j.cpc.2021.107905

Cited by 15 publications

(20 citation statements)

References 38 publications

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“…In fact, using the Fourier transform of these four electron densities and the entire experimental data cube, that is, photoemission intensity as a function of ( E B , k [11̅0] , k [001] ), we can deconvolute the emissions into molecular orbital contributions. , The resulting deconvolution curves are shown in Figure b, using the same color code as that for the MOPDOS plot in panel c, together with a k ∥ -integrated energy distribution curve (EDC) shown as a black dashed line. The good agreement between the deconvoluted experimental spectra and the MOPDOS from the DFT calculation gives us further confidence in the assignment of the molecular emissions and also in the exceptionally strong surface-induced charge transfer into the LUMO + 1.…”

Section: Resultsmentioning

confidence: 99%

Demonstrating the Impact of the Adsorbate Orientation on the Charge Transfer at Organic–Metal Interfaces

et al. 2021

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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.

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Section: Resultsmentioning

confidence: 99%

Demonstrating the Impact of the Adsorbate Orientation on the Charge Transfer at Organic–Metal Interfaces

et al. 2021

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“…Photoemission simulations have been carried out for the isolated molecules within the PW approximation, with the initial state being supplied by DFT calculations (i.e., the well-known photoemission tomography method , ). The geometric structures of gas-phase BPPP and BPF are comparatively flat, so we neglected the inevitable change of geometry upon adsorption on the substrate.…”

Section: Resultsmentioning

confidence: 99%

Orbital Mapping of Semiconducting Perylenes on Cu(111)

et al. 2021

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Semiconducting O-doped polycyclic aromatic hydrocarbons constitute a class of molecules whose optoelectronic properties can be tailored by acting on the πextension of the carbon-based frameworks and on the oxygen linkages. Although much is known about their photophysical and electrochemical properties in solution, their selfassembly interfacial behavior on solid substrates has remained unexplored so far. In this paper, we have focused our attention on the on-surface self-assembly of O-doped biperylene derivatives. Their ability to assemble in ordered networks on Cu(111) singlecrystalline surfaces allowed a combination of structural, morphological, and spectroscopic studies. In particular, the exploitation of the orbital mapping methodology based on angleresolved photoemission spectroscopy, with the support of scanning tunneling microscopy and low-energy electron diffraction, allowed the identification of both the electronic structure of the adsorbates and their geometric arrangement. Our multi-technique experimental investigation includes the structure determination from powder X-ray diffraction data for a specific compound and demonstrates that the electronic structure of such large molecular self-assembled networks can be studied using the reconstruction methods of molecular orbitals from photoemission data even in the presence of segregated chiral domains.

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“…In the POT approach ( 25 , 50 ), the final state Ψ f is approximated by a PW. Thereby, the photocurrent I i arising from one particular initial state i turns out to be proportional to the Fourier transform normalΨtrue~ifalse(boldkfalse)of the initial-state wave function multiplied by the polarization factor ∣ A ∙ k ∣ 2 Iifalse(k‖false)∝∣boldA∙boldk∣2 ∣normalΨtrue~ifalse(boldkfalse)∣2…”

Section: Methodsmentioning

confidence: 99%

“…The δ function ensures energy conservation, where Φ denotes the sample work function, E i denotes the binding energy of the initial state, and ℏω denotes the energy of the exciting photon. The transition matrix element is given in the dipole approximation, where p and A , respectively, denote the momentum operator of the electron and the vector potential of the exciting electromagnetic wave ( 50 ).…”

Section: Methodsmentioning

confidence: 99%

Momentum space imaging of σ orbitals for chemical analysis

et al. 2022

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Tracing the modifications of molecules in surface chemical reactions benefits from the possibility to image their orbitals. While delocalized frontier orbitals with π character are imaged routinely with photoemission orbital tomography, they are not always sensitive to local chemical modifications, particularly the making and breaking of bonds at the molecular periphery. For such bonds, σ orbitals would be far more revealing. Here, we show that these orbitals can indeed be imaged in a remarkably broad energy range and that the plane wave approximation, an important ingredient of photoemission orbital tomography, is also well fulfilled for these orbitals. This makes photoemission orbital tomography a unique tool for the detailed analysis of surface chemical reactions. We demonstrate this by identifying the reaction product of a dehalogenation and cyclodehydrogenation reaction.

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kMap.py: A Python program for simulation and data analysis in photoemission tomography

Cited by 15 publications

References 38 publications

Demonstrating the Impact of the Adsorbate Orientation on the Charge Transfer at Organic–Metal Interfaces

Demonstrating the Impact of the Adsorbate Orientation on the Charge Transfer at Organic–Metal Interfaces

Orbital Mapping of Semiconducting Perylenes on Cu(111)

Momentum space imaging of σ orbitals for chemical analysis

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