Real-time X-ray scattering studies on temperature dependence of perfluoropentacene thin film growth

We report on real-time scattering investigations of growth of thin films of Perfluoropentacene (PFP) and its dependence on the substrate temperature, ranging between $−120°C$ and $60°C$⁠. All films were grown up to 50 nm on silicon oxide. We find that along with the known thin-film phase, there is also a coexisting molecular arrangement with a unit cell twice the size with respect to the long axis. Furthermore, we observe that even at temperatures as low as $−20°C$ PFP shows a high degree of crystallinity in the out-of-plane direction. The growth of PFP is characterized by a two-stage process, where the molecular lattice experiences a much stronger in-plane relaxation in the thickness regime $0–19 nm$ compared to the thickness regime $19–50 nm,$ which can be probed only by $in situ$ real-time scattering measurements.