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.