Structural analysis of zinc phthalocyanine (ZnPc) thin films: X-ray diffraction study

X-ray diffraction (XRD) was used to analyze the structure of thermally evaporated zinc phthalocyanine (ZnPc) organic thin films, as functions of the substrate temperature and film thickness. A metastable α to stable β phase transformation has been observed when the films are coated at higher substrate temperatures. The core structure of the zinc phthalocyanine macrocycle is formed by four isoindole units, which endows the molecule with a two-dimensional conjugated π electron system. The structural analysis and high-resolution transmittance electron microscope images, along with simulation, support the formation of molecular arrays, with the electronic structure fixing the molecular spacing and producing mainly parallel arrays in small domains. These arrays produce the frontier orbital gap, which match the experimental values, and also the experimental data of periodicity, which can be reproduced theoretically.