Substrate-Induced Phase of a Benzothiophene Derivative Detected by Mid-Infrared and Lattice Phonon Raman Spectroscopy

Benedikt Schrode*, Andrew O.F. Jones, Roland Resel, Natalia Bedoya, Robert Schennach, Yves Henri Geerts, Christian Ruzié, Michele Sferrazza, Aldo Brillante, Tommaso Salzillo, Elisabetta Venuti

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


The presence of a substrate-induced polymorph of 2,7-dioctyloxy[1]benzothieno[3,2-b]benzothiophene is probed in microscopic crystals and in thin films. Two experimental techniques are used: lattice phonon Raman and IR spectroscopy. The bulk crystal and substrate-induced phase have an entirely different molecular packing, and therefore, their Raman spectra are characteristic fingerprints of the respective polymorphs. These spectra can be unambiguously assigned to the individual polymorphs. Drop-cast and spin-coated thin films on solid substrates are investigated in the as-prepared state and after solvent-vapor annealing. Because Raman spectroscopy is less sensitive with decreasing film thickness, IR spectroscopy is shown to be a more feasible tool for phase detection. The surface-induced phase is mainly present in the as-prepared thin films, whereas the bulk phase is present after solvent-vapor annealing. This result suggests that the surface-induced phase is a metastable polymorph.

Original languageEnglish
Pages (from-to)993 - 1000
Publication statusPublished - 2018


  • Crystal growth
  • Polymorphism
  • Raman spectroscopy
  • Surface analysis
  • Thin films

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Physical and Theoretical Chemistry

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