The collective orientation barrier (COB), an energy barrier to form standing orientation in organic thin film growth, has been proposed as a new effective index of molecular orientation control. The COB for pentacene (PEN)/graphene (Gr), a system with strong molecular substrate interaction, was investigated and compared with that for PEN/SiO2, a system with weak substrate interaction. As a result, 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 and controlling an effect of substrate interaction on molecular orientation.
