ORIENTATIONAL ORDERING OF DOMAINS IN VACUUM-GROWN OLIGOMER THIN-FILMS- A SCANNING FORCE MICROSCOPY STUDY

We investigate by Scanning Force Microscopy the effects of the deposit ion temperature on the ordering of sexithienyl thin films grown on mic a in high-vacuum. The low-temperature aggregates are formed by isotrop ic grains, while elongated lamellae appears, as the temperature increa ses which align along directions of the mica lattice. This change in t he film morphology does not correspond to a discontinuity in the param eter which describes the anisotropy of the domains, while it makes the slope of the orientational order parameter (2nd Chebyshev polynomial) of the domains to change discontinuously. We infer that the transitio n is second-order or weak-first order, and we locate the corresponding transition temperature.