Effect of Co-evaporant Induced Crystallization on Needle Growth of Phthalocyanine Thin Films

Needle growth control of metal-free phthalocyanine (H2Pc) films was performed by using a recently proposed method, co-evaporant induced crystallization. Nominally 200nm of H2Pc films were grown on indium tin oxide (ITO) coated glass substrates with substrate heating of 70 and 40 degrees C. The morphologies were observed by using scanning electron microscopy (SEM), and the crystallinities were confirmed by X-ray diffraction (XRD). Various lengths of needles were observed in the H2Pc films grown without co-evaporant. With co-evaporant, in contrast, rather uniform and shorter needles with larger diameters were grown. These results suggest that the co-evaporant enhances rather 2-dimensional-growth than 3-dimensional-growth of organic films.