Impact of graphene-molecular interaction on collective orientation barrier for organic film growth

Abstract

The temperature-dependent molecular orientation variation of pentacene (PEN) on a graphene-covered substrate (PEN/Gr) was investigated via p-polarized multiple-angle incidence resolution spectrometry (pMAIRS). The temperature regime of the orientation transition of PEN/Gr was different from that of PEN/SiO₂. The collective orientation barrier (COB), an energy barrier that molecules need to overcome to form a standing orientation, was estimated via pMAIRS. Consequently, the COB of PEN/Gr was found to be 10 times larger than that of PEN/SiO₂. This indicated that the COB is valuable for understanding the effect of substrate interaction on molecular orientation.