Solid to Quasi-Liquid Phase Transition of Submonolayer Pentacene

This is the authors' abstract. We don't add key points for this paper.

Based on surface charge states, the thermodynamics of pentacene molecules exhibit intriguing structural transitions with various temperatures. On an SiO 2 surface, the mean tilt angle decreases with increasing temperature, whereas three different structural regimes form on the Au surface. To understand these contrasting temperature dependencies of molecular orientation on the two surfaces, a model wherein the tilt angle has two stable states is proposed in this study. Consequently, the pentacene crystals undergoes a phase transition at a relatively low temperature of 350 K, thus indicating a hidden factor governing the morphology of molecular crystals, and providing insights into the thermal behavior of physisorbed organic molecules.