The Role of Molecular Arrangement on the Dispersion in Strongly Coupled Metal-Organic Hybrid Structures

Autor: Rödel, Maximilian, Lisinetskaya, Polina, Rudloff, Maximilian, Stark, Thomas, Manara, Jochen, Mitric, Roland, Pflaum, Jens
Rok vydání: 2021
Předmět:
Druh dokumentu: Working Paper
DOI: 10.1021/acs.jpcc.1c10084
Popis: Metal-organic hybrid structures have been demonstrated a versatile platform to study primary aspects of light-matter interaction by means of emerging states comprising excitonic and plasmonic properties. Here we are studying the wave-vector dependent photo-excitations in gold layers covered by molecular films of zinc-phthalocyanine and its fluorinated derivatives (FnZnPc, with n = 0,4,8,16). These layered metal-organic samples show up to four anti-crossings in their dispersions correlating in energy with the respective degree of ZnPc fluorination. By means of complementary structural and theoretical data, we attribute the observed anti-crossings to three main scenarios of surface plasmon coupling: i) to aggregated $\alpha $-phase regions within the FnZnPc layers at 1.75 eV and 1.85 eV , ii) to a coexisting F16ZnPc $\beta $-polymorph at 1.51 eV, and iii) to monomers, preferentially located at the metal interface, at 2.15 eV. Whereas energy and splitting of the monomer anti-crossings depend on strength and average tilting of the molecular dipole moments, the aggregate related anti-crossings show a distinct variation with degree of fluorination. These observations can be consistently explained by a change in FnZnPc dipole density induced by an increased lattice spacing due to the larger molecular van der Waals radii upon fluorination. The reported results prove Au/FnZnPc bilayers a model system to demonstrate the high sensitivity of exciton-plasmon coupling on the molecular alignment at microscopic length scales.
Comment: Artikel 23 pages, 5 figures; Supplement Information: 15 pages, 3 figures; Submitted to ASC Photonics
Databáze: arXiv
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