Identification of an organic semiconductor superlattice structure of pentacene and perfluoro-pentacene through resonant and non-resonant X-ray scattering

• Published in: AIP advances Vol. 5; no. 11; pp. 117241 - 117241-7
• Main Authors: Kowarik, S., Hinderhofer, A., Wang, C., Weber, C., Gerlach, A., Hexemer, A., Leone, S. R., Schreiber, F.
• Format: Journal Article
• Language: English
• Published: Melville American Institute of Physics 01-11-2015; American Institute of Physics (AIP); AIP Publishing LLC
• Subjects: Crystal structure; Crystallinity; Dependence; MATERIALS SCIENCE; Optoelectronic devices; Organic semiconductors; Reflectance; Reflectivity; Semiconductor growth; Soft x rays; Superlattices; Thin film structure; X-ray scattering
• ISSN: 2158-3226; 2158-3226
• DOI: 10.1063/1.4936884

Highly crystalline and stable molecular superlattices are grown with the smallest possible stacking period using monolayers (MLs) of the organic semiconductors pentacene (PEN) and perfluoro-pentacene (PFP). Superlattice reflections in X-ray reflectivity and their energy dependence in resonant soft X-ray reflectivity measurements show that PFP and PEN MLs indeed alternate even though the coherent ordering is lost after ∼ 4 ML. The observed lattice spacing of 15.9 Å in the superlattice is larger than in pure PEN and PFP films, presumably because of more upright standing molecules and lack of interdigitation between the incommensurate crystalline PEN and PFP layers. The findings are important for the development of novel organic quantum optoelectronic devices.