Phase Transition in Copper Phthalocyanine Thin Films Observed in Surface Morphology

The surface morphology of organic semiconductor thin films determines the material performance for gas sensor and photovoltaic applications. Structural control of copper phthalocyanine thin films is achieved via post-annealing, altering the deposition temperature, and bi-thermal film deposition. The phase transition manifests in x-ray diffraction measurements through a peak shift from 6.8° to 7.0°. Simultaneously, the crystalline shape and alignments change in atomic force microscopy (AFM) images. At the α to β phase transition, the AFM images show local areas of both phases coexisting, while the x-ray diffraction data reveals only one phase. Thin films deposited sequentially at two deposition temperatures enable the production of crystals with predictable grain sizes, roughness, and surface morphologies.