Ac160ts probes

The morphology of the samples was investigated employing an Asylum Research MFP-3D AFM system operating under ambient conditions. Olympus AC160TS probes were used with typical force constants of 20–80 N/m and tip curvature radii of 5–7 nm. AFM topography images of the samples were processed using the open source software Gwyddion (version 2.38). The thickness of the molecular crystals was estimated considering the total volume on the device active area and presented as an equivalent in complete monolayers (ML) of the bulk structure (in the case of 6P considering up-right standing molecules that form island-like crystallites) of the molecular crystals, since an ideal layer-by-layer growth was not observed. In the considered ranges of the growth temperatures, only the monoclinic β-phase of 6P crystallites is expected (the Baker structure) and the fcc structure of C₆₀. The morphology of C₆₀ films indicated layered growth (step edge height of ~0.8 nm), while 6P films were found to consist of both, islands of up-right standing molecules (~2.6 nm) and needles with flat-laying molecules (taller than 10 nm).