The effects of fluorination and side-chain addition on core-level spectra of anthracene

Shashank S. Harivyasi1, Egbert Zojer1, Gian Paolo Brivio2 and Guido Fratesi3

1.Institute of Solid State Physics, NAWI Graz, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria

2.Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, Via Cozzi 55, 20125 Milano, Italy

3.Dipartimento di Fisica, Università degli Studi di Milano, Via Celoria, 16, 20133 Milano, Italy

The performance of organic electronic devices depends to a significant extent on the interfaces that form in these devices; this makes the investigation of organic-inorganic interfaces a topic of active research. Over the past few decades, X-Ray Photoelectron Spectroscopy (XPS) and Near-Edge X-Ray Absorption Fine Structure Spectroscopy (NEXAFS) have emerged as standard tools for analyzing organic thin-film structures adsorbed on inorganic surfaces. Simultaneously, the theoretical understanding as well as the ability to simulate and disentangle the experimental features has also been developed. Overall, this makes XPS an effective tool to reveal adsorption-induced changes in the chemical environment of the thin film and NEXAFS to determine its spatial orientation.

In this poster, we present the results from density functional theory calculations of XPS and NEXAFS spectra. We compare the XPS spectra for anthracene and perfluorinated anthracene molecules to determine the chemically-induced core-level shifts that arise due to the fluorination. The analysis of NEXAFS spectra provides additional information on how valence states are affected. Considering the many initial and final states relevant in a NEXAFS process, which is even larger for perfluorinated anthracene, we find a comparison of theoretical and experimental spectra crucial for properly understanding the various spectral features. Last we discuss the consequences of side-chain addition to the molecule (relevant for SAM formation) and highlight its impact on the simulated NEXAFS spectra.