Homoepitaxy Growth of Well-Ordered Rubrene Thin Films

Rubrene is a nonplanar molecule, it is recognized that only amorphous rubrene films can be obtained on such substrates as Au, SiO 2, and Al 2 O 3 by organic molecular beam deposition or ordinary vacuum evaporation. In this work, rubrene organic single crystals with very smooth surfaces were used as substrates. Well-ordered rubrene thin films were obtained by ordinary vacuum evaporation, and the substate temperature is room temperature. Two-dimensional nucleation-monolayer by monolayer growth and homoepitaxy was demonstrated when the deposition rate was kept at 0.2 nm/min. Furthermore, when the deposition rate was increased to 0.6 nm/min, two-dimensional hexagons were observed in the growth process of rubrene thin films and are similar to the two-dimensional islands with regular shapes observed in homoepitaxy growth of inorganic thin films.