Growth Mechanism of Large-Size Rubrene Single Crystals Grown by a Solution Technique

Abstract

Large-size and high-quality rubrene single crystals have been grown by a solution technique. The biggest crystal has 4 mm dimension. Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy both indicate that the crystals obtained are pure rubrene and did not incorporate the solvent at the detection level. The morphology of surface and transect of the rubrene single crystals was observed by optical microscope, atomic force microscope (AFM), and scanning electron microscope (SEM). Three-dimensional nucleation was happened on the surface of single crystals. The array of small and large straight steps was observed on the surface of the rubrene single crystals. Layer-like structures were also observed on the cross-section of single crystals. All results indicate that each large step is most probably formed from the piling of small steps and the growth mechanism of rubrene crystals grown from solution is probably a three-dimensional nucleation–layer-by-layer periods growth.