Modern in situ real-time X-ray scattering and nucleation theory for an enhanced understanding of molecular self-assembly

Abstract

Quantifying nanoscale processes that drive the self-assembly of organic molecules into functional thin films is the prerequisite to understand and steer structure formation. In a study on the growth of PTCDI-C8 we unravel a remarkable layer-dependent molecular diffusion behaviour from an innovative simultatineous in situ acquisition of X-ray reflectivity growth oscillations and diffusively scattered X-rays and the application of state-of-the-art nucleation theory. This allows us to determine nucleation energies, critical cluster sizes and attempt frequencies.[1] These quantities can be strongly influenced when applying chemical tuning to well-known molecules. We showcase this on the example of the growth of 6P and 6PF2. As a result of the fluorination we achieve a significant film smoothening as desired for applications, where an efficient in-plane charge carrier transport is of importance.