Annealing-induced phase transition in zinc phthalocyanine ultrathin films

Hyeyoung Ahn,Ting-Chang Chu

doi:10.1364/ome.6.003586

Abstract

We report the evidence of post-annealing-induced phase transition in zinc phthalocyanine (ZnPc) ultrathin (~20 nm) films upon annealing at 200 °C. The signatures of phase transition are observed in their morphological, structural, and ultrafast spectroscopic properties. X-ray diffraction measurement shows that α-phase nanospheres transform to β-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 β-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.

Highlights

Phthalocyanines (Pcs) are two-dimensional aromatic molecules with an inner ring
We report the evidence of post-annealing-induced phase transition in zinc phthalocyanine (ZnPc) ultrathin (~20 nm) films upon annealing at 200 °C
Tight packing of molecules in the β-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

Summary

Introduction

Phthalocyanines (Pcs) are two-dimensional aromatic molecules with an inner ring. The π-π orbital overlap and electrostatic interactions between adjacent Pc cores induce disc-like Pc molecules to self-assemble into one-dimensional columnar structures in condensed phases.

Results

Conclusion