Alignment-induced epitaxial transition in organic-organic heteroepitaxy.

We report the epitaxial growth of thin films of a small organic molecule (pentacene) on polymer substrates with controllable photoalignment over a wide range. The pentacene molecular plane exhibited a distinct orientational change from parallel to perpendicular relative to the polymer chain with increasing substrate polymer alignment. Each orientation consists of twinlike domains. Such characteristics reveal a unique alignment-induced epitaxial transition controlled by the subtle balance of weak interactions, showing a promising approach for tuning the characteristics of organic semiconductor based electronic devices.