Annealing-induced phase transition in zinc phthalocyanine ultrathin films

Abstract

We report the evidence of post-annealing-induced phase transition in zinc phthalocyanine (ZnPc) ultrathin (similar to 20 nm) films upon annealing at 200 degrees C. The signatures of phase transition are observed in their morphological, structural, and ultrafast spectroscopic properties. X-ray diffraction measurement shows that alpha-phase nanospheres transform to beta-phase nanorods that have a high degree of crystallinity with an excellent ordering along the c-direction in a monoclinic arrangement. Tight packing of molecules in the beta-crystallites allows a red-shift and intensity gain of the lowest-energy subband in the Q-band and subsequently increases the electronic coupling in both intercolumn and intracolumn paths. (C) 2016 Optical Society of America