N. Mrkyvkova, A. Cernescu, Z. Futera, A. Nebojsa, A. Dubroka, M. Sojkova, M. Hulman, E. Majkova, M. Jergel, P. Siffalovic and F. Schreiber
J. Phys. Chem. C 125, 9229 (2021)
The development of defect analysis for inorganic semiconductors in the past century paved the way for the success story of today’s electronics. By analogy, defect analysis plays a critical role in developing and improving devices based on organic molecular semiconductors. However, because of weak molecular interactions, absent in inorganic semiconductors, device-relevant thin organic films are susceptible to the formation of defects in the molecular orientation, which in turn have a profound impact on the performance in the optoelectronic applications. To address this problem, we broaden the applicability of scattering-type scanning near-field optical microscopy (s-SNOM) and utilize the light-induced anisotropic response of vibrational modes to reveal the defects in molecular orientation. We show that in the case of molecular islands with steep crystal facets only the scattered s-SNOM optical amplitude can be exploited to describe the molecular arrangement reliably, while the phase-based analysis leads to artifacts. The presented s-SNOM analysis of molecular defects can be universally applied to diverse topographies, even at the nanoscale.