TY  - JOUR
AU  - Cojocariu, Iulia
AU  - Sturmeit, Henning Maximilian
AU  - Zamborlini, Giovanni
AU  - Cossaro, Albano
AU  - Verdini, Alberto
AU  - Floreano, Luca
AU  - D'Incecco, Enrico
AU  - Stredansky, Matus
AU  - Vesselli, Erik
AU  - Jugovac, Matteo
AU  - Cinchetti, Mirko
AU  - Feyer, Vitaliy
AU  - Schneider, Claus Michael
TI  - Evaluation of molecular orbital symmetry via oxygen-induced charge transfer quenching at a metal-organic interface
JO  - Applied surface science
VL  - 504
SN  - 0169-4332
CY  - Amsterdam
PB  - Elsevier
M1  - FZJ-2020-04755
SP  - 144343 -
PY  - 2020
AB  - Thin molecular films under model conditions are often exploited as benchmarks and case studies to investigate the electronic and structural changes occurring on the surface of metallic electrodes. Here we show that the modification of a metallic surface induced by oxygen adsorption allows the preservation of the geometry of a molecular adlayer, giving access to the determination of molecular orbital symmetries by means of near-edge X-ray absorption fine structure spectroscopy, NEXAFS. As a prototypical example, we exploited nickel tetraphenylporphyrin molecules deposited on a bare and on an oxygen pre-covered Cu(1 0 0) surface. We find that adsorbed atomic oxygen quenches the charge transfer at the metal-organic interface but, in contrast to a thin film sample, maintains the ordered adsorption geometry of the organic molecules. In this way, it is possible to disentangle π* and σ* symmetry orbitals, hence estimate the relative oscillator strength of core level transitions directly from the experimental data, as well as to evaluate and localize the degree of charge transfer in a coupled system. In particular, we neatly single out the σ* contribution associated with the N 1s transition to the mixed N 2px,y-Ni 3dx2-y2 orbital, which falls close to the leading π*-symmetry LUMO resonance.
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000502040600103
DO  - DOI:10.1016/j.apsusc.2019.144343
UR  - https://juser.fz-juelich.de/record/888201
ER  -